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Land Records Glossary




  1. Ability of a computer to reference a specific data set (single record, file, group of files, other) by identifying a specific sector of memory or the disk drive (server) where it is stored for the purpose of editing, assembling, manipulating and/or directing this data set to a peripheral devise.
  2. Portion of the operating system dedicated to locating a body of data and making it available to the user for viewing, analyzing, and/or editing purposes.

Accuracy: Closeness of results of observations, computations, or estimation of spatial features to their true value of position. "Absolute Accuracy" is the differential between the actual real world location of a point on the surface of the earth and its mathematically assigned geographic coordinate.

Address Matching: Process that compares a table of addresses to the address attributes of a theme to convert textual addresses to locations on a map. Street name and address values are compared to DBMS records to find the street segment with a matching name and address range. The address is then located at a prorata distance from the street segments startpoint proportional to the addresses value relative to the street's address range value and on the appropriate side of the street (even addresses always on the right, etc.).

Algorithm: Step-by-step problem-solving procedure, especially an established, recursive computational procedure for solving a problem. Set of ordered procedures, steps, or rules usually applied to mathematical calculations, and assumed to lead to the solution of a problem in a finite number of steps; the logic (and/or formula) that is used to solve a problem. Typical Algorithms possess the following characteristics:

  • Application to a particular problem results in a finite sequence of steps.
  • Unique initial step.- Predicated on the results it derives, each step has a unique successor.
  • Terminates with either the solution or an error message stating that the problem has no solution.

Alphanumeric: Combination of alphabetic letters, numbers and/or special characters. A mailing address is an alphanumeric listing. The designation ljsdoijwe92393 is an alphanumeric word. Alphabetic characters consist of letters A through Z. Numeric characters consist of the characters 0 through 9... sometimes excludes () and * / \.

AM/FM: Acronym for Automated Mapping/Facility Management, a computer-based Land Information System (LIS). It is used to produce, edit, archive and correlate Automated Map features with nongraphic facility related design or operation attibutes. Primarily applies to systems that support infrastructure operations. Spatial data management system that support the utility and public works operations, maintenance, planning, analysis, and accountability of utility infrastructure systems such as sewer, water, natural gas, telephone and cable networks, electrical, and storm drainage.

Analogue: In the context of remote sensing and GIS, refers to data in graphical or pictorial form as opposed to digital form. Generally, refers to a quantity which is continuously variable, rather than one which varies only in discrete steps.

Annotation: Text or labels plotted graphically on a map or drawing. Text labels for naming such map features as streets and places; unique identification numbers assigned to individual map features including parcels, utility nodes and links; dimensioning; posted notes and instructions; descriptive text used to label area features such as soil types, zoning categories. Annotation is typically primitive map features and is not intelligently associated to the map feature and/or possible linked DBMS records.

ANSI: Acronym for American National Standard Institute that organizes committees of computer users and manufacturers to develop and publish industry standards. ANSI standards are used by US firms as guidelines, although they may be modified.

Application: Use of software, data, procedures and techniques in a series of steps that are then put into practice to solve a problem or perform a function.

  1. Of or being a computer program designed for a specific task or use.
  2. Also referred to as a GIS project.

Application Solution: A combination of spatial data structures, symbol libraries, data dictionaries, attribute formats, linked DBMS configurations, menus, icons, dialogs, software executables, productivity enhancements, tutorials and focused documentation that together provide a total environment for building, maintaining and operating a GIS or AM/FM database.

Arc: Locus of points that forms a linear feature in a spatial database that is not closed.

  1. A set of XY coordinates used to represent a linear feature or a polygon boundary. It is a continuous string of XY coordinate pairs (vertices) beginning at one location and ending at another location, having length but no area.
  2. A coverage feature class used to represent linear features and polygon boundaries. One linear feature can contain many arcs.
  3. In CAD it is a curvalinear feature defined by such location combinations as
    • Center point, radius, and starting point
    • Center Point, Start and End Point.
    • Start point, end point and one point in between others.

Architecture: Set of data, processes, and technologies that together make up the physical and communication system supporting information management operations. There are data architectures for the database system. There are software architectures that support the computation, analysis, and processing aspects of the organization. There are technology architectures that support the hardware and network configurations.

ASCII: Acronym for the "American Standard Code for Information Interchange", a standard way to represent text. Because ASCII text contains no formatting (fonts, underlines or special characters), it can be read by all computers. A convention for using digital data to represent printable characters that provide compatibility for data communications. Used for information interchange between different computer systems. A set of 128 characters used for communication between computers and word processing systems. An ASCII File, also referred to as a text files, is made up of text records each of which contains only letters, numbers, punctuation symbols and control codes.

ASCM: Acronym for the American Society of Civil Engineers.


  1. Horizontal direction in which a slope faces, or the exposure, commonly expressed in degrees clockwise from north.
  2. Compass direction facing downward in the direction of the steepest slope (maximum rate of decent. For example, if the declination from north of the steepest gradient were 90 degrees, the aspect (or exposure) would be west-facing. Aspect maps display the general orientation of each area of land typically according to eight regimes: N NW W SW S SE E NE.

Asynchronous Communications: Transmission of data via serial lines without a specific timing pattern. Transmission of data in which each character is a self-contained unit. Intervals between characters may be uneven.


  1. Single element of nongraphic data assigned to a spatial feature either as an imbedded data element within the spatial database or located in a linked DBMS data record.
  2. Descriptive characteristics of a feature, site or phenomenon.
  3. Location is a mandatory attribute.
  4. Set or collection of datum that describe the characteristics of real-world conditions.

Automated Mapping: Computer-aided process for creating, editing and manipulating cartographic information. The resulting computer-generated files are a compilation of primitive drafted spatial features.

Automated Polygon Processing (APP): Software utility that transforms primitive vector boundaries and text labels into polygon data models able to support spatial analysis operations. A second function typically supported is intersecting multiple polygon overlays to formulate composite polygon overlays and linked attribute records describing the combination of conditions present in each newly crated polygon.


Bandwidth: Usually measured in bits-per-second, it is another way of stating how much"

Base Map:

  1. Basic representation of a region of the earth as it would appear if viewed from above.
  2. Portrays basic reference information onto which other information of a specialized nature is placed. Usually shows the location and extent of natural earth surface features and permanent man-made objects.
  3. Contains basic digital survey control and topographic elevation reference framework for integrating all of the other map features of a particular geographic area.

Baud Rate:

  1. Speed at which information can be transferred through a COM (serial) Port. Measured in bits per second. For example, a 28,80000-baud transmission device moves data at a rate of 28,800 bits per second.
  2. Number of signal elements sent over a communication line (modem, printer...) in a single second.

BBS: Acronym for a Bulletin Board System, a computerized meeting and announcement system that allows people to carry on discussions, upload and download files, and make announcements without the people being connected to the computer at the same time.

Bit Map (also Bitmap): Image stored as a pattern of dots. A way of storing the digital representation of an image in which bits are referenced (mapped) as rectilinear picture elements (pixels). In color graphics, an individual value is used for each red, green and blue component of a pixel.

Block Feature: Aggregation of primitive spatial features grouped together to represent a single spatial feature, typically in the form of a symbol within a spatial database.

Block Group: U.S. Census Bureau term that refers to a set of U.S. census blocks combined together to provide a small population and housing census area. All selected census Blocks are contained within a single census tract boundary containing an average of population of 800(+/-), about one fourth to one fifth the population of a census tract.

Boolean Operations:

  1. Of or relating to a logical combinatorial system which treats variables such as propositions and computer logic elements, through the operators AND, OR, NOT, IF, THEN, and EXCEPT.
  2. Within multiple sets of polygon feature, operations that produce their union, intersection, complement and exclusion.

Boundary: Indicates a border or limit. Typically designate the extents of such divergent areas as a school, water, sewer and flood control districts, community planning areas, zoning designations, soil conditions, geologic formations, parcels and easements.


  1. System capability to find a defined feature or set of features in a database.
  2. In regards to the World Wide Web, they also access multiple communication systems including WAIS, Gopher, FTP and telnet.


  1. Area within a specified distance (radius) around a selected map feature(s).
  2. Operation that creates a new entity by tracing around an entity or entities at a constant distance. For example, the buffer around a point is a circle.


CAD: Acronym for Computer Aided Drafting, a computer aided process for interactively creating modifying and manipulating spatial information. Mathematical integrity of the spatial model is adequate to support legal survey and engineering design requirements.

CAD/GIS: Refers to integrating Geographic Information System technology with that of Computer Aided Design Systems.

Cadastre: Official map records pertaining to location, quantity, value and ownership of land parcels within a government jurisdiction. Polygon overlay of parcel boundaries, each containing a PIN (Parcel ID Number) and linked non-graphic DBMS tables of supporting land tenure and other pertinent information for the primary purpose of taxation. See Multipurpose Cadastre.

CAE: Acronym for Computer Aided Engineering, software that performs such engineering design functions as structural, stress-strain, grading, pressure distribution, hydrological, load lost, and other analysis.


  1. In vector mapping, the adjustment of the digitizing tablet so that a location on the manual map corresponds to the location of the cursor within the display of the spatial database. To implement, XY values of known coordinates within the survey control network are entered in conjunction with screen selections of the corresponding locations on the map sheet to be digitized.
  2. In remote sensing, these are parameters pertaining to spectral and/or geometric characteristics of a sensor or radiation source.

CAMA: Accronym for Computer Aided Mass Appraisal, a standard for managing Assessors information. The CAMA Interface Direct Query Application (CIDQA) is used to analyze CAMA data.

Cartesian Coordinate: Point whose location is expressed in terms of its distance above or below an X, a Y and a Z coordinate plane. Location of a point on a plane is expressed by two coordinate values, one representing the distance from the Y axis and the other representing the distance from the X axis.

Cartography: Science and art of making maps and charts. More broadly, the term includes all the steps necessary to produce a map: planning, aerial photography, drafting, editing, color separation, and multicolored printing. With regard to computerized spatial databases, a cartospatial feature is a point, line, arcs, string, chain, polygons, symbol, text or other form of spatial entity. Functionality of cartographic information systems is limited to encoding, displaying and measuring cartospatial features.

Cell: Basic element of spatial information in a grid data set.

  1. A cell map is generally made up of a spatial grid of rectilinear spatial units (sometimes square) of same size and shape, each depicting a condition assigned to all areas within the cell relative to a selected measurement. Such values are typically stored in a linked attribute table.
  2. The location of a single value in a database defined by intersecting a row or record with a field or column.

Census Data: Official, usually periodic, enumeration of a population, often including the collection of related demographic information. The U.S. Census Bureau conducts a census of the U.S. Population every ten years and publishes detailed descriptions of subgroups within the overall population for a variety of purposes. The U.S. Census Bureau organizes this data according the following hierarchy of designated census areas.

Census Tract: subarea of a county or city containing an average of approximately 4000 inhabitants that have statistically comparable population characteristics, economic status, and living conditions.

Block Group: Subset of a Census Tract containing a population of approximately 800.

Census Block: Subset of a Block Group, the smallest geographic area for which census data is collected.

Centerline: Linear feature representing the midpoint along a linear element like a road or stream.

Centroid: Any point used to label the location of a feature in a spatial database (polygon, line or point).The geometric center of polygon; may be calculated as the average location of all vertices of a polygon boundary. Any single location within a polygon, arithmetically derived or not, to which attribute information about that polygon area is linked. Midpoint of a line to which attribute information about that line is linked.

Character String: A consecutive sequence of alphanumeric characters (i.e. ABC,def,123) used together as a single unit for purposes of display or analysis.


  1. Data that are devoid of errors.
  2. Process for identifying and correcting potential errors in digital map line work. For example, closed polygon areas made up of boundary segments wherein the location of the end point of one segment is identical with the start point of the next segment.
  3. In other words, line work free of gaps and dangles.


  1. Communications between computers. The client computer is typically a desktop microcomputer device using a software program to contact and obtatin data from a server computer. The server is typically a minicomputer, workstation, or mainframe computer integrated over a network. However, the server can be a micro-computer linked to multiple storage devices.
  2. In context with the Internet, the client is any computer that can access an Internet service. For example, there are Gopher clients and telnet clients. The server is a central computer from which a particular service takes place. For example, there are FTP servers and Gopher servers.

COGO: Acronym for Coordinate Geometry, COGO is a subsystem of CAD or GIS made up of a set of standard procedures for processing survey data such as bearings, distances and angles to generate precise spatial representation of land features and survey control networks.

Commit: To make permanent any changes to the database implemented during the current transaction.

Compiler: Program for translating instructions written in a high-level computer language into machine instructions.

Composite Mapping: Overlaying and combining data types from two or more map overlays to create a map displaying:

  1. Combination of these characteristics.
  2. Combination of information from different thematic maps.
  3. Map containing the combined characteristics of multiple overlapping spatial data layers.

Computer Aided Drafting (CAD): Computer-aided process for creating, modifying and manipulating spatial information. Typical operations are interactive wherein a user either requests immediate results in the creation of new spatial features or modification of existing spatial features. The mathematical integrity of the spatial model is adequate to support legal survey and engineering design requirements.

Concatenation: Arrange (strings of characters) into a chained list. For example, the text strings.

Conflate (or Conflation): To meld or fuse two or more components into one whole. With regard to GIS, to merge two or more spatial data sets into one.

Conformal Projection: A projection wherein the scale is the same in every direction at any point. Meridians and parallels intersect at right angles; the shape of small areas and angles with very short sides are preserved. Most area values are distorted.

Conic Projection: A projection in which the surface is drawn as it would appear if projected on a cone wrapped around the Earth. A Lambert projection is a form of Conic projection often used for maps of the continental United States, France, and other countries.

Connectivity: Topological property of lines and nodes being linked or attached to each other, typically pertaining to infrastructure networks such as utility and transportation systems.

Continuous Map: Treats the entire service territory as one large map and hence one large file. More complex than tiled mapping systems because of the need to reference the entire database in order to act on any one part of it.See Tiled Mapping Systems.

Contour Mapping: Display of contour lines, each of which represents a constant value, typically elevation, throughout its length. Also called an Isoline map, it displays linear features that connect all points having the same numeric value (i.e. elevation, rainfall, noise, concentration level).

Conversion: Translating manually displayed spatial information (drawing maps and diagrams) into digital spatial databases.

Corridor Analysis: Procedure used to identify the extents of corridors of land area containing candidate routes for such linear transportation features as highways, pipelines, and electric transmission. Land use / environmental data overlays are prepared for the areas within the selected corridors which are subsequently used to determine explicit and relative measurements for comparing alternative routes and assessing the selected route in terms of construction cost, environmental impact, and operational effectiveness.

Cover: Environmental data overlay that defines the surface of the earth in terms of vegetation type in non developed areas (i.e., forest, rowcrops, orchards, grasslands) and land use type in developed areas (residential, transportation, vacant, light industrial). Land cover map overlays can be derived from interpretation and classification of remotely sensed images.

CPU: Acronym for Central Processing Unit. The portion of a computer which directs and supervises all of its functions (screen, printer, disks....) and controls the interpretation and execution of instructions assigned by a program called theoperating system (OS).

Cyberspace: Name for a whole range of information resources available though computer networks. Originated by William Gibson in his novel.

Cylindrical Projection: Projection in which a surface is drawn as it would appear if projected on a cylinder wrapped around the earth. "Mercador Projection" is a form of cylindrical projection in which the surface is drawn as it would appear if projected on a cylinder wrapped around the earth in a north south direction.


Data Field: A column or item in a database. Individual data item within a row or record. The logical equivalent of a database column. Another term for domain or column. Specified area within a record for placing a particular category of data.

Data Flow Diagram: A picture of the flows of data through a business activity or automated system that illustrates the external agents, internal processing, and data communication.

Data: General term for information including facts, measurements, classifications or value representations from which conclusions can be inferred. Things known about real-world entities; results of observations or measurements of such features. A single datum has three potential components:

  1. "Attributes", attributes describing the substance characteristics variables, values, and similar qualities of the datum.
  2. "Geographic", information describing the position of the datum in space relative to other data.
  3. "Temporal", information describing the instant or period of time for which the datum is valid.

Database Design: Structure of a database. In spatial data management systems, refers to both the spatial and tabular parts. A collection of interrelated data sets stored together and controlled by a specific schema for efficient management of information. A consistent and specified set of procedures is used in building, maintaining, accessing, and interrogating information from a database.

Database Management System (DBMS): An acronym for Database Management System, a computer-based system or application software that enables users to build and maintain a non-spatial database. The DBMS performs a variety of data access, edit, query and reporting operations. DBMS can also refer to the collection of software required to use and manipulate a tabular databases to present multiple different views of the data.


  1. Point, line or surface used as a reference for a measurement of another quantity. Point, line, or surface used as a reference (i.e., surveying, mapping, or geology).
  2. Combination of parameters and control points used to accurately define the three dimensional shape of the Earth (spheroid). For example, the North American Datum for 1983 (NAD83) is the basis for map projections and coordinates within the United States and throughout North America.

DBMS Record: In the context of spatial databases, a record in a data table external to the spatial database that contains attribute information corresponding to a specific map feature.

Decision Support System: Focuses on complex decision making situations and the problems most often faced by an organization+s decision makers. A computerized process designed to provide decision makers what they need to know when they need to know it including pertinent up-to-date maps, tables, graphs, photos, histograms and charts to make the most informed decision possible.DefaultAn automatically designated value, setting, or an action automatically taken, unless otherwise specified. Values or parameter settings defined by the software vendor or the system user that are applied automatically during data entry, editing, and/or analysis operations unless changed by the user. For example, a default snap radius is set at 5 model units unless the current polygon processing transaction requires a different one to be applied. For data models there can be default symbol libraries, file and attribute naming conventions, DBMS configurations, interface links, and spatial database formatting schemes.

Demographic: Data Characteristics of human populations, such as size, growth, density, distribution, and vital statistics. Sociologic/ Economic data concerning the human environment.

Density Map: Symbols produced randomly in polygons or grid cells with each symbol representing a numerical count (i.e. ten households, one gas station).

Digital Data: Anything in computer readable format usually stored on magnetic tape or disk.Spatial or attribute data stored in electronic format, digital units, on a hard drive.Discrete numerical representation of information vs. analog representation.

Digital Elevation Model: Digital cartographic representation of a terrain surface or a subsurface feature as defined by a series of three dimensional coordinate values. A digital representation of a continuous variable over a two dimensional surface by a regular array of Z values referenced to a common datum.

Digitize: Process of tracing hard copy documents on a tablet to capture line work in digital form. The process of converting existing data from paper maps, aerial photos, or raster images into digital form by tracing the maps on a digitizer. Feature locations are encoded as X,Y coordinates.

DIME File: Acronym for Dual Independent Map Encoding, a data format used by the U.S. Census Bureau to encode street network and related data for the 1980 Census. See TIGER for details.

Dissolve: Removing boundaries between adjacent polygons having the same value for a specific attribute. Combining polygons that would otherwise be assigned the same color or hatch pattern in a thematic map display. Process of aggregating neighboring polygons based on a matching value for some attribute.

Distributed: Processing System of computers connected together by a communications network. In true distributed processing, each computer system is chosen to handle its local workload while the network supports the system as a whole.

Document: May be a textural report, spreadsheet, picture, or spatial database stored as a file in the computer. Typically, a document is a file containing plane ASCII text. It is a file created within an application, for example, a letter created in a word processor or a graph created in a spreadsheet or graphics program.

DOS: Acronym for Disk Operating System developed for IBM by Microsoft Corporation that has become a de factor standard Microcomputer operating system. A system program that allows transfer of programs and data back and forth from the computer processor and the disk drive.

Draping: Display of selected two-dimensional data on a perspective view of certain relief or any other spatially distributed variable. For example a map of a road network may be draped over a perspective view of a 3D terrain surface.

Drawing File: Digital CAD equivalent of a hard copy document. Some systems refer to them as designs or design files. A collection of graphical features stored as a set of spatial information in a computer.

DTM: Acronym for Digital Terrain Model, a representation of terrain relief in a computer readable format. Also referred to as a Digital Elevation Model.

DXF: Acronym for Data Exchange Format, a standard spatial data exchange format for CAD systems. DXF files contain ASCII or binary (DXB) records each of which describes a vector complete enough so that it can be converted into a spatial feature by any spatial database management product able to process these files.

Dynamic Segmentation: Functionality for modeling linear features in a transportation or other network related applications. Process of dynamically locating events along linear features straight from attribute tables in which attributes are recorded according to distance from a start point. The ability to translate data collection in linear (milepost) measures into:

Posted point and symbol features adjacent to an alignment representing incidents or facilities.

Break points along an alignment wherein each resulting route segment has a unique set of assigned physical and/or operational attributes.


Easting/Northing: Within a State Plane coordinate system, Easting is the equivalent of the longitude and Northing is the equivalent of the latitude of a location described in terms of distance from an origin point defined for each project or state.

Edge Matching: Map cleanup function that allows for distortion between adjacent maps to produce a true match of features at the edges of maps. The result is a continuous map by ensuring that all features that cross theboundary between two adjacent maps appear to be or are a single feature.

Editing: Detection of errors in text records or spatial database features and the implementation of the needed correction. Corrections can include additions, deletions, and rearrangements, as well as changing size, font, style, color, orientation, alignment, scale, and rotation. Editing techniques exclusive to spatial features include changing elevation, thickness, width, attribute assignments, surface textures, dimensioning and others.

EIS: Acronym for an Executive Information System, a read-only information system or extension of a larger information system designed for upper level managers and decision makers to view and interrogate data but not make any changes.

E-mail: Acronym for Electronic Mail, messages sent from one person to one or many persons via computer.

Engineering Design Precision: Extremely precise standard that is mandatory for a variety of applications. An example is the land base used to provide positional reference for capital improvement project contract drawings. The geographic location of a map feature displayed on these drawings should meet the accuracy standards required by local ordinance. Given an established Survey Control Network grid of one mile or denser, a recommended standard could be all control points having an absolute accuracy of 1 foot or better and all referenced points having a relative accuracy of 2 feet or better.


  1. Single feature in a spatial database such as a line or circle. In some systems entities are referred to as elements.
  2. Geographic feature that exists and is distinguishable in the real world. For example a land parcel, road, building, manhole, or pole.For the purposes of this glossary, the term feature is used interchangeably with entity.

Ethernet: A local area network originally developed by Xerox DEC and Intel that interconnects personal computers via coaxial cable. A type of computer network established using coaxial cable twisted pair cable or fiber optic cable. It has a network protocol defining the physical and data link layers of the Open Systems Interconnect (OSI) model. (See OSI).

Expert System: Computer system using rule-based logic to simulate human intelligence. Performs tasks that require a high level of knowledge of certain subjects and extensive specialized training. Involves parallel processing hardware and software technology that utilizes combinatorial mathematics. Together, search engines, able to perform the logical inferences needed to automatically expand the domain of the system+s knowledge base, are developed. Confronted with a question, expert systems are able to ask more questions to acquire the additional information needed for a competent answer.


Facility Management: In conjunction with Automated Mapping, the record keeping of information concerning spatially distributed assets or facilities. Typically used for asset accountability and maintenance management operations. There is no spatial component. If a spatial component is added so that records in a Facility Management system are linked to features in an Automated Mapping System, the combination is referred to as an AM/FM system.

Facility Map: Maps of specific components of urban infrastructure such as a water main, street pavement, telephone pole, or street light. Within a spatial database system, facility maps are typically encoded as series of individual layers in conjunction with the land base.

Feature Locking: Method for preventing a second user from editing a feature while the original user is performing an edit. Locking prevents writing on a feature by others while a feature or record is currently "checked out" for modification. When a transaction is started, the selected feature, and in some cases the linked attribute record, is designated as locked in such a manner that no other user can write on the feature until it is released (the lock designation is removed).

Feature: Natural and man-made Geographic features represented by points/symbols, lines, and areas on a map. Object in a geographic or spatial database with a distinct set of characteristics. A defined aspect of the earth's surface that is not further subdivided. For example, a road segment, manhole, building, or area designated having the same soil type.

Fence: User defined rectilinear, circular, or polygon border that defines an area in which all enclosed feature are selected (selection set) for subsequent operations. Typical operations include changing of spatial properties of all features in the selection set or isolation of all linked DBMS records for subsequent query and/or analysis. A fence can also be an open polygon used to select all spatial features that touch or pass through it.

Field: Columnar data item in a DBMS.

File: In computing, a collection or set of related digital data stored on a computer disk and accessed / retrieved according to an assigned unique name. A collection of related computer records grouped under a common heading and containing data according to specific units.

Fill: Solid coloring covering an area bounded by linear or curvilinear segments. A solid color rendering of a polygon, sometime referred to as a "solid fill".

Filtering: Process of removing unwanted components from tabular or spatial data.

  1. In vector spatial database, a variety of smoothing algorithms used to reduce file size by removing excessive turning points along a linear feature.
  2. In raster databases, a mathematically defined operation used in image classification that removes long range (high-pass) or short range (low-pass) variations.

Fire Wall: Combination of hardware and software that separates a comunications network into two or more parts for security putposes.

Font: One of the attributes describing the appearance of linear feature or text string.

  1. For spatial data, a user-defined set of instructions that determine, among other parameters, the appearance of a linear feature including dash and gap lengths, number of parallel lines, line widths, and spacing and description of embedded letters or symbols.
  2. For textural or spatial data, a complete set of text type of one size and typeface in which font designates a set of text characters of a particular style.

Format: The physical structure of an item. The order in which information is prepared and presented.

  1. The arrangement of data for storage or display. A file format is the specific design of how information is organized in a collection or set of related digital data.
  2. To divide (a disk) into marked sectors so that it may store data.
  3. To determine the arrangement of (data) for storage or display.

Fractal: A geometric pattern that is repeated at ever smaller scales to produce irregular shapes and surfaces that cannot be represented by classical geometry. Fractals are used especially in computer modeling of irregular patterns and structures in nature.

FTP: Acronym for File Transfer Protocol, a standardized way of transmitting files on the Internet.


Generalization: Wherein a general class contains constituent classes.

  1. In thematic mapping, boundaries between polygons that contain like attributes are dissolved (i.e. all categories of residential land is generalized under the simpler classification of residential; all categories of sanitary sewers are mapped as a single utility type.
  2. The process of simplifying line work by removing or combining vertices. This can be done manually or automatically.

Geocoding: In spatial databases, a coding process wherein a digital map feature is assigned an attribute to serve as a unique ID (tract number, node number) or classification (soil type, zoning category). In polygon processing, the polygon boundary that contains the coordinate pair of a data item (text label) is assigned the value of that data item as "geocode".

Geodesy: Science or art of measuring the shape and size of the earth's surface, or large parts of it, as distinguished from surveying which deals only with limited tracts of the earth.

Geographic: Data Model (GDM)Total combination of spatial data structures, symbol libraries, data dictionaries, attribute formats, linked SQL DBMS configurations, menus, icons, dialogs, software executables, and productivity enhancements that together provide an overall framework for building, maintaining and operating an AM/FM or GIS database.

Geographic Information System (GIS): NOTE: The following is not an attempt to provide a single generic definition.

  1. Computerized decision support systems that integrate spatially referenced data. These systems capture, store. retrieve, analyze and display spatial data.
  2. An organized assemblage of computer hardware, software, spatial data and operating instructions designed for capturing, storing, updating, manipulating, analyzing, and displaying all forms of geographically referenced information.
  3. A manual or computer-based system for geographic data input, storage, manipulation, analysis, modeling and output. The system is used to improve geographic question-asking and problem-solving, and to enhance the overall geographic decision-making process.

GNIS: Acronym for Geographic Name Information System.

Gopher: A method of making menus of materials available on the Internet. A client/server type problem requiring the user to have a Gopher Client progam. Although there are still thousands of Gopher sites on the Internet, it is anticipated that they will be superceded with by Hypertext (See Hypertext).

GPS: Accornym for Geograhic Position System, hardware and software designed to communicate with satellites to determine ground location.

Graphic User Interface: Software standard used to establish the menus, screens, dialog boxes, buttons, edit boxes, picklists, toggles, radio buttons, command input, and viewing screens used to communicate instructions to the computer and for the computer to communicate findings back to the user.

Graphic/Nongraphic Interface: Two-way interface between the spatial database (drawing) and the nongraphic DBMS table. Supports instructions sent from the spatial database requesting specific operations to be performed by the supporting DBMS, and instructions sent from the DBMS requesting specific transactions to be performed by the spatial database (i.e. change the color, fill pattern, width or thickness of associated spatial features).

Gray Scale: Generally refers to a monochrome ordering of 256 shades between black and white which are assigned to raster picture elements (pixels) according to reflected light, heat, and/or other relative intensity measurements. Most common digital display option for scanned black and white orthophotos.

Grid Cell Map: Map displaying spatial information in the form of color coded, equal sized rectangle, squares, equilateral triangles or hexagons. The color of the cell determined by the condition assigned to the cell according to a uniformly applied rule regarding the condition (i.e. geologic classification):

  1. Present in the center of the cell.
  2. Makes up the greatest percentage of the cell area compared to the other conditions present,
  3. Determined by a scoring system applied to selected spatial overlays. (See Relative Suitability).

GRID: Acronym for Global Resource Information Database, a regular or nearly regular repeating pattern of equally sized geographic areas including squares, rectangles, equilateral triangle, or regular hexagon. Equal sized array of spatial cells arranged in columns and rows.

Ground Control: Point on the surface of the earth with known coordinates as represented by some geographic grid reference system. The location of ground control points can be represented on maps and other cartographic products, and can serve as reference points with which to rectify the scale and accuracy of cartographic products to the actual area on the ground that is represented.


Hard Breakline: Linear map features that designate the location of such sharp changes in surface relief as retaining walls, curbs and drainage ditches. Superimposed on a TIN (array of 3D triangular faces), they introduce a bias so that the applied surface modeling process generates a 3D surface and/or contour map that accurately defines these near vertical to vertical features.


  1. Titles displayed across the top of a database table that describes the content of each data field.
  2. First record in a data file that contains identifying information and instructions that apply to all other components of the file or data set it contains.
  3. In image files, a header stores information about format and/or registration coordinates.

Hierarchical Database:

  1. A branching information storage system such that one record serves as the base. From this parent record, the data structure branches out to reference subordinate child records, which in turn branch out to more detailed records.
  2. Database system in which the most significant information is stored in the most easily accessible location and the less significant dependent data is stored in subordinate less accessible locations.

High Level Language: Programming languages such as BASIC, PASCAL, or C++ that enable programmers to develop software applications using ordinary words and symbols rather than binary numbers. Also referred to as forth generation languages. Typically a compiler transforms any one statement in such programs into many specific computer instructions.

Highlight: Spatial features linked to DBMS records that meet the conditions of a logical and/or spatial search query are displayed differently so that they can be visually differentiated from those that did not. Typical techniques include changing their color, width, fill or hatch pattern, or in 3D views, thickness. Also applies to image enhancement techniques (See Image Processing).

Homepage: Space on the World Wide Web.

HTML: Acronym for for HyperText Markup Language, a coding alanguage used to create Hytpertext couments for usin the World Wide Web. You can specify that a block of text, or a word, is "linked" to another file on the Intenet.

Hybrid: Combination of two different formats together. For example, a vector data overlay draped on top of a raster image.

Hypertext: Any text embedded in a computer display that "links" to other documents. Other documents are displayed by simply double clicking on a Hypertext Word.


Image Processing: Computer techniques used to interpret and manipulate raster data including:

  1. Enhancement - aid in the interpretation of an image by changing the display color and/or intensity of pixels (highlighting) that represent areas that share a common set (or range) of physical characteristics.
  2. Rectification - Fitting the image to a map base by eliminating distortion due to the curvature of the earth, position of the camera or scanner, and/or varying terrain elevation.
  3. Classification - Assigning pixies within an image to one category (land cover, soil category, etc.) or another according to their associated relative intensity measurements.
  4. Data Merging - superimposing vector data on top of image data.


  1. Digital representation of spatial data stored in raster format. Scanned photos, maps, diagrams, or remote sensing data (aerial photos, satellite scenes, radar telemetry) electronically stored as a raster (pixel) data set made up of either binary or integer values representing (singular or multiple) reflected light, heat, and/or other relative intensity measurements.
  2. Exact copy of data in a file transferred to another medium.
  3. One of the three kinds of Data (spatial, textural and image).

Incident Map: Geographic display of the location in which an event took place such as a crime, accident, fire, or reported health hazard or disease. Typically used to examine patterns of occurrences of a specific condition or class of conditions.

Indexing: Logically ordering information components by the values present in a key field. An identifier used to access stored information. DBMS table ID field of other data feature used to expedite locating a specific record (text, images, spatial) within a database.

Industry Standard: Widely accepted and commonly used operating systems, software, data formats, network protocols, and procedures that are compatible on wide a variety of commonly used hardware platforms. A format of data or a type of software commonly used within a professional discipline.

Information System: Computer system that has the ability to perform data collection, assembly, interrogation, visualization and communication.

Information: Collection of data organized in a manner that is used to support the decision making process. Knowledge derived from experience, instruction and or study. Communication of knowledge. Data processed into a more meaningful form through comparison, summary, classification, and association. See Knowledge.


  1. Underlying operational framework especially for an organization or a system.
  2. Basic facilities and services needed for the functioning of a community or society, such as transportation and communications systems, water and power lines, and public institutions including schools, post offices, and prisons.

Inset Map: More detailed (larger scale) representation of a specific area on a map usually placed in an uncluttered portion of the same sheet as the smaller scale main map.

Interactive: Procedure that requires regular input from the end-user. A back and forth dialog between the user and a computer. Typically a point-and-click user interface to easily create and edit spatial database features. In digitizing, procedure by which a system user converts a manual drawn image into a digital format for use spatial databases. Display capabilities which support real time spatial manipulation. Dialog between user and computer in a sequence of requesting instructions and responsive computer prompts.


  1. Surface forming a common boundary between adjacent regions, bodies, substances, or phases.
  2. Junction between two or more components of an information system. Typically, the link between the spatial database and nongraphic (DBMS) databases.
  3. Point of interaction or communication between a computer and any other entity, such as a printer or human operator.

Internet: World-wide international communications network comprised of thousands of government and academic networks each of which is using TCP/IP protocols. (See TCP/IP).

Interoperability: Communication between different computer systems. Seamless accessing and sharing of multiple data structures across multiple hardware platforms, operating systems and application software. For example, software A using hardware B being able to access and operate on data C.

Interpolation: Process of inserting, estimating, or finding a value intermediate to the values of two or more known points in space. Estimation of an elevation value at an unsampled point based on the known elevation values of surrounding points. Process of inserting, estimating, or finding a value intermediate to the values of two or more known points in space.

Intersection: Set of elements that contains elements shared by two or more given sets of elements. In spatial analysis, polygons within two or more overlays are combined together to form a composite polygon overlay made up of an array of closed "sub-area" polygons, each of which is assigned a list of attributes that describe the combination of conditions present within its boundary. Such attribute tables may reside in external DBMS or tables stored within the spatial database. See Overlay.

Intranet: Any two or more small number of computer networks connected together.

Island: In spatial databases, an island is a polygon wholly contained within another polygon.

ISP: Acronym for Internet service provider, an institution that provides access to the Internet in some form, usually for money.


Join: Combing two tabular data sets into a single one based on a common field. Two tables with a common domain combined into a single table. SQL query that retrieves data from two or more sources at once based on matching field values.


Key Map: A highly generalized map used to provide a contexture reference for retrieving more detailed spatial data sets for specific geographic areas.


  1. Familiarity, awareness, or understanding gained through experience or study.
  2. Sum or range of what has been perceived, discovered, or learned about a specific body of information.



  1. Text annotation posted on a map near a spatial feature.
  2. Same as one wherein the source of the value of each label is from a linked database record.
  3. Symbol or set of symbols identifying the contents of a file, memory, tape, or record.

LAN: Acronym for Local Area Network a communications system that typically consists of PCs with adapter cards, file servers, a network operating system, printers and gateways to departmental or corporate computers. Typically serves a small geographic area of a single building or campus of buildings.

Land Base: Spatial overlay comprised of multiple layers of primitive spatial features that provide a locational reference to other spatial features in the spatial database. It also includes a framework of competent survey data that provides a precision control network. The land base is also referred to as a base map. See Cadastre.

Land Information System (LIS): Manual or computer-based system used to establish, operate, maintain, and analyze facilities, resources and/or activities within a defined geographic area. The LIS also includes the underlying information management infrastructure required to access, apply, update and store this information.

Land Use: Sub-set of a Planning and Zoning Automated Mapping System.

Latitude/Longitude: Latitude describes the angular distance that a location is north or south of the equator. Longitude describes the angular distance that a location is east or west from the prime meridian at Greenwich, England.

Layer: Logical grouping of data to be viewed individually or in combination. Similar in concept to transparent acetate overlays of manual spatial information systems. A distinct set of spatial features that are dealt with together.

Legend: An explanation of the symbols, codes, names given variables and other information appearing on a map drawing or chart. Includes a sample of each symbol, line pattern, shading, or hatching appearing on the map along with annotations describing the meaning of each.


  1. Distinct set of spatial features that are dealt with together.
  2. Position along a vertical axis; height or depth.
  3. Sub-category of data, for example a subset of soil codes within the overall category.

Line Smoothing: A variety of smoothing algorithms used to reduce file size by removing excessive turning points along a linear feature according to a user defined filter algorithm. See Filtering.

Line: In spatial databases, a linear vector with only a start and end point, containing no intermediary (shape) turning points. A line feature is the alignment between two points representing within a spatial database a real world or theoretical feature, e.g., a road, stream or parcel boundary.

LIS: Acronym for Land Information System. Manual or computer-based information system used to store, retrieve, display, and plot spatial and textural data relating primarily to land features and characteristics. Addresses a wide range of existing natural and cultural aspects of land within a mapped area including property ownership, tax assessment, zoning, land use, vegetation, soils, geology, hazardous areas, noise zones, surface and subsurface hydrology, flora and fauna, visually and/or ecologically sensitive areas. Can also include overlays that address infrastructure systems including transportation, sewer, water, storm, electric, cable, and telephone and storm drainage.


  1. Distinct place in the real world.
  2. Position defined by a set of coordinates within a spatial database (i.e. pole, property corner, reported crime incident.)
  3. The storage space of digital data within an information storage system.

Logical Connection: Within a utility network topology, if the position setting of a link physically connected to a node is defined as "On" relative to that node, then this link is logically connected to that node.

Lookup Table:

  1. Database table that assigns display parameters to each value in a field to generate thematic maps.
  2. A list of values that are correlated to a range of other values. For example, according to a soil type name, reference to this table can identify the corresponding compressive strength, percolation, and erosion potential rating.
  3. A file that correlates a user defined ID number permanently assigned to a spatial feature with machine readable ID number that is subject to occasional change.


Machine Independent: The quality of computer programming languages or operating system software that enables programs to run on a variety of computers without extensive reprogramming.

Machine Readable: Instructions coded so that a computer can recognize and execute them.

MacOS: Operating System for MacIntosh Personal Computers produced by Apple Computers.


  1. Sequence of commands executed as one command.
  2. Series of specialized procedures or instructions in a computer language that can be replaced by a set of instructions which customize and streamline basic software functions.
  3. Recorded often complex sequence of keystrokes and mouse actions that can be played back with a single or simple combination of keystrokes.

Mainframe: Central Processing Unit, main memory, and control units of a computer typically housed in one large cabinet or in a number of smaller ones grouped together. The term only applies to large computers.

Map: Representation, usually on a plane surface, of a region of the earth or heavens. Within a spatial database, an assembly of digital spatial features that represent a set of real-world features and the geographic relationships between them. This representation may exits digitally, manually (i.e. on paper), or in the human mind.

Mapematics: Mathematics used in conjunction with creating maps, measuring map features, defining map accuracy, or other mapping functions that require quantification.

MarkCharacter: A feature in a file or record used to locate a specific point or condition.


  1. Rectangular array of numeric or algebraic quantities subject to mathematical operations.
  2. Something resembling such an array, as in the regular formation of elements into columns and rows.
  3. Network of intersections between input and output leads in a computer, functioning as an encoder or a decoder.


  1. Unit of a computer that preserves data for retrieval.
  2. Capacity for storing and remembering information for subsequent reference.
  3. An organized set of locations in which a computer can store and find data instructions. Such capacity stored in Random Access Memory microchips (RAM) is referred to as virtual memory.

Menu: Options for command input by computer users rather than typing instructions at the command line. Menus come in many forms including permanent screen menu squares, pull-downs, popups, sliders, icons, cursor, picklists, dialog and toolbar buttons, as well as printed tablet menus and cursor buttons on digitizing (mouse) devices.


  1. Combine items from two or more similarly ordered sets into one set that is arranged in the same order.
  2. Splice separate but adjacent mapped areas into a single data set.
  3. Annotate spatial features with attribute values retrieved from selected fields within linked DBMS records. Typically users can control the size, angle, style, color, font, and offset of these posted labels.

Meta-Data: Data about data. This often includes the data's source, accuracy, data type, projection, date of origination and other general descriptions.

Microcomputer: Very small computer, such as a laptop or personal computer, built around a microprocessor as its CPU and designed to be used by one person at a time; smaller than a minicomputer.

Minicomputer: A medium sized computer, usually fitting within a single cabinet, serving the needs of multiple users within a small organizational unit. Has more memory and a higher execution speed than a microcomputer. Also referred to as a workstation or midrange.

MIPS: Acronym for Millions of Instructions Per Second, a CPU related performance measurement.


  1. Applying structured rules and procedures to one or more spatial database overlays to conduct spatial and/or network analysis to derive new information to aid in problem solving and planning.
  2. Schematic description of a system, theory, or phenomenon that accounts for its known or inferred properties and may be used for further study of its operational characteristics.
  3. Process of simulation, prediction and description involving changing the parameters and generating/communicating new model results. Using spatial or network overlays to simulating a process to predict outcomes to what-if scenarios.

Modem: Abbreviation for MODulator and DEModulator, a device that converts data from one form into another.

  1. From one form usable in data processing to another form usable in telephonic transmission.
  2. Send and receive information over communication lines between computers, usually over telephone lines.

Mosaic: Public Domain World Wide Web browser with graphic capabilities (gif but not jpeg) developed by the National Center for Supercomputing Applications (NCSA) at the University of Illinois at Urbana - Champagn and available for general use at no charge.

Multimedia System: Combined use of several media types, such as video, computer graphics, animation, movies, slides, music, and lighting especially for the purpose of education or entertainment. Integrating multiple technologies on a single platform with a single user interface.

Multipurpose Cadastre: Comprehensive land information system at the parcel level. Land base includes all parcel boundaries, right-of-ways, and easements with each parcel typically linked to supporting attribute records. Other components typically include highly precise survey control network and other information overlays addressing a wide range of natural and cultural characteristic as well as supporting infrastructure systems. See Land Information System.


Network Analysis: Specialized queries that reference connected linear and node features.

  1. Typical analytical transactions within Transportation Networks:
    • Modifying direction and/or impedance along links and through intersections.
    • Identifying the optimal path as measured between two or more points according to a selected terms of measurement.
    • Highlighting all components (nodes and links) of the optimal path, referred to as "routing".
  2. Typical analytical transactions within Utility Networks:
    • Modifying direction and ON/OFF position settings of links relative to nodes.
    • Isolating all network nodes and links both physically and logically connected to a selected test point.
    • Highlighting all logically connected network features, referred to a "Network Tracing". Attribute records linked to highlighted features can be subsequently isolated to perform design analysis.
  3. Two types of utility networks:
    • Pressure Networks. Typical transactions include resetting valves to redirect service operations or reset switches to reconfigure circuits. Typically applies to water, gas, steam, electric and telephone systems.
    • Gravity Networks. Typical transactions include isolating all nodes and links upstream or downstream from a test point. Can include isolating a portion of the network by changing position settings of links relative to their upstream or downstream nodes to OFF. Typically applies to sewer, storm, telephone, and sometimes electric utilities.
  4. Typical analysis performed using records linked to highlighted features in a route or trace include load loss, traffic demand and capacity, pressure loss, maximum flow, gradient, asset management and other engineering analysis.

Network Connectivity: Characteristic of a network topology that enables users to perform network analysis functions. See Network Analysis, Network Link, Network Node, Transportation Network, Utility Network.

Network Link: A straight or multi-vertex linear feature that connects any two end points (nodes) in a manner that is determined by the topology type being addressed as follows:

  1. Polygon - a polygon edge.
  2. Utility Network - a linear unit in a connected series of nodes and linear units, typically including attributes regarding its own (from-to) ID, the ID of the Node at each of its ends, and the position setting at each its end (ON or OFF) relative to the Node at each of its ends.
  3. Transportation Network - a linear unit in a connected series of node and linear units. Typically includes linked attributes regarding its own ID, flow direction, and impedance (length, friction coefficients, maximum speed, and others).

Network Node: End point of a link represented by a point or symbol. Characteristics of a node is determined by the tolology to which they are a component part.

  1. Polygon topology - The intersection of two or more polygon segments.
  2. Utility Network - contains list of all links connected to it which are typically assigned as attributes.
  3. Transportation network is a list of all connected links as well as node impedance factors such as traffic control devises and turning constraints which are typically assigned as attributes.
  4. Communications and/or computer network, a single terminal.See Transportation and Utility Networks.

Network Routing: In transportation networks, this refers to highlighting all node and link features along the optimal path between a starting point and one or more destinations, either in terms of least distance, travel time, or other prescribed performance criteria. See Transportation Networks, Network Connectivity, and Network Analysis.

Network Tracing: In utility networks, this refers to highlighting all node and link features within a gravity of pressure network that are both physically and logically connected to a test point within the network according to a specified set of rules. See Utility Network, Network Analysis, Network Link, and Network Node.

Nongraphic Database (also Nonspatial): Set of tabular data records, each record containing multiple data fields. In the context of spatial databases, one of these fields is the Unique ID Number of a corresponding map feature.

NSDI: Acronym for National Spatial Data Infrastructure. See National Academy of Science.


Object: Something perceptible by one or more of the senses, especially by vision or touch; a material thing. Another term for a "feature" within a spatial database. For the purposes of this glossary, the term feature is interchangeable with object.

On-The-Fly: Temporary performance of a calculations when needed. An instruction that is transparently invoked by the user according to conditions encountered during an a transaction. Automatic Boolean operations that add, modify or skip certain processing steps under a particular set of conditions. For example, when adding a new spatial feature, the ID number of the previously encoded feature is defined along with the default rules for sequentially generating the "next" ID number to be used, modified or ignored.

Open System: An implementation of industry standards such that incompatible operating systems, hardware platforms, and application software are tied together to create compatible computing environments. System integration that adopts standards that enable diverse software and data platforms to be efficiently accessed and used by all members within an organization. Typically means that the adopted standards are determined though a consensus of interested parties rather than a single or limited number of venders.

Optical Fiber: Bundles of transparent glass or plastic strands able to transmit billions of bits of information per second in the form of light pulses generated by lasers. Telephone companies are systematically replacing conventional copper wire (metallic) with these enclosed thin glass wires, vastly increasing the variety and quality of services that can be offered to consumers. In addition to speed, optical systems are not subject to interference from random radiation in the environment as are metallic systems.

Organization Activity: Anything an organization does toward achieving a stable purpose. An activity may be a process or a mandated function.

Orientation: Attribute of spatial features that describes the angle at which it is turned from its normal north south axis. Applies particularly to text or symbols, two point line features, and entire blocks of spatial features. For example, a water hydrant with an orientation of 30 degrees would be viewed with a declination of 120 degrees from the horizontal plane.

OSI Layers: Acronym for Open System Interconnection, it is made up of seven layers of data communication:

  1. Physical: Functional characteristics for electronic data transmissions.
  2. Data Link: Node to node integrity measure of electronic data transmission.
  3. Network: Route between sending and receiving stations (i.e., switching functions of dial-up telephone system).
  4. Transport: Transmission end-to-end integrity and validity.
  5. Session: Orderly coordination of communications (i.e., making sure that an entire message is properly received).
  6. Presentation: Common format for transmitting data between incompatible systems (i.e., ASCII, binary, etc.).
  7. Application: Communication system access rules used by a program to communicate with other programs.

Out-Of-The-Box: Refers to a software or hardware system with a user interface so intuitive that it can be implemented without training nor reference (maybe some) to on-line or manual documentation.

Overlay: Something that is laid over or covers something else.

  1. In a manual graphic information system, a transparent sheet containing graphic information, such as labels, symbols or colored areas, defined in a manner to expedite being viewed and interpreted in conjunction with other data overlays with a common coordinate system.
  2. In an automated spatial information system, same as a manual system except that all overlays are in a digital format for viewing and interpretation on a CRT screen. Each overlay defines a specific aspect of the spatial database.
  3. Typical overlays could include land use, soils, watershed boundaries or drainage system overlays, each of which is a single or set of multiple layers within the spatial information system. 4) Also refers to the intersection of two polygon layers to make a third composite overlay (i.e. soils overlaid with land use to define runoff conditions). See Intersection.

Overshoot: Situation where a digital line extends past the intended boundary line. This extension past the intended juncture point is called a dangle.


Parallel Communications: Data transmission wherein multiple wires simultaneously carry one data bit at a time greatly increasing the rate that data can be sent over a single wire. However, distance restrictions between components limit their use to being internal to a single device or between devices within a single room.

Parcel: A portion of the earth defined by a boundary inside of which certain assigned rights apply regarding occupancy and/or use of land, air or water apply. Can also include linked attributes that define the rules and conditions for to excersicing these rights.

Parent Child Links: Technique wherein attribute lists in two different tables are joined together to function as a single DBMS table. Indexing on a common ID record in both the parent (core) and child (subordinate) table, three different kinds of links can be initiated: One-to-one: For every record in the parent table there is one and only one record in the child table with a matching ID in the indexing fields (i.e. Parcel Record and Water Customer Record - common field: Parcel Number). One-to-Many: For every record in the parent table, there may be one or more records in the child table with a matching ID in the indexing fields (i.e. Building record and Asbestos incidence record - common field: Building #). Many-to-One: For every record in the child table, there is more than one record in the core table with a matching ID in indexing fields (i.e. Parcel Record and Zoning Ordinance Description - common field: Zoning Ordinance Number).

Photogrammetry: In surveying and mapping, the science, art and technology of obtaining reliable measurements and maps from photographs. Means for measuring or plotting planimetric, topographic, and other features of the earth through the use of aerial photographs and ground control.

Physical: Connection within a utility network topology, a link is physically connected to a node when one of the links end points is located at its insert point.

Pixel: Abbreviation for Picture Element, the smallest nondivisible image-forming unit of a plot or video display. Each cell can have assigned attributes, in addition to color. In raster processing, pixels refer to a single cell within a matrix of grid cells. See Image, Image Processing.

Plan-And-Profile: Typically a improvement plan document wherein the:

Upper Portion defines an orthographic view of the land base and the horizontal alignment of a linear facility such as a roadway, pipeline, transmission line, or railroad.

Lower Portion defines the vertical alignment of the same facility indicating the natural ground elevation and elevation of various facilities (road bed, pipe invert elevations, manholes, vaults, etc.). Used to support facility planning, design, and construction.

Planimetric Map: Horizontal depiction of map features on a two-dimensional plane without any reference to contours or topographic relief. Typical features defined within a planimetric map include such natural and cultural features as streams, roads, shorelines, waterways, building footprints, reservoirs, bridges, roadways, overpasses, sidewalks and parking lots.

Point: Single X,Y (optionally Z) location in space. Dimensionless geometric feature having no other spatial properties except location. Many different natural and man-made features are modeled as points in a spatial database including trees, hydrants, poles, building, etc.

Pointer Attributes: Attribute data associated with a spatial feature that describes its positional and operational relationship with adjacent, contiguous, or other features in the spatial database.

Point-In-Polygon: A spatial query that determines which polygon boundary encompasses a specified point. Typical operation is to select multiple points within a boundary and assign to them an attribute equal to a characteristic assigned to all areas within the boundary (i.e. soil type) to the attributes describing the point. As a variation, one or more polygons are selected and all points within them are likewise assigned new attributes. Process can be extended to apply to linear features (line-in-polygon) and closed polygons (polygon-in-polygon) located within or partially within polygons as well.

Polygon Overlay:

  1. A group of polygons on one or more layers, representing various areas that make up a particular geographic theme (i.e., soil types, zoning designations, parcels, land use, etc.).
  2. Spatial analysis function that uses Boolean logic to combine two sets of polygon boundaries to create a third that represents an intersection or union of the first two.


  1. Closed plane figure bounded by three or more line segments with a nonzero area. Many different natural and man-made features are typically represented by polygons in a spatial database including soil types, water bodies, building footprints, lot boundaries, etc. Multisided feature that represents an area on a map.
  2. A type spatial query wherein the spatial selection area is a polygon shape rather than a square, rectangle, or circle.

Position Setting: User-defined (ON/OFF) pointer attribute describing the logical relationship of the end of a Link with the Node to which it is physically connected.

Precision: In general, precision refers to how close a measured value matches another measured value.

  1. Degree of exactness with which a quantity is stated (i.e., the number of significant decimal places in an expressed coordinate value).
  2. Can be expressed in terms of "repeatability" of a measurement, I.e., the likelihood of deriving the same coordinate values from the same mathmatical calculations.
  3. In spatial databses, refers to how many places allocated to the storage of coordinate information.

Primitive Features: Spatial features within a spatial database that have no associated attributes or auxiliary information.

Productivity Enhancement: Increases the rate at which goods or services are produced especially output per unit of labor. Portion of user interface that simplifies or speeds up routine tasks such as data entry, data editing, spatial data processing, query building and complex analysis steps that would otherwise require numerous keystrokes to initiate.

Projection: Mathematical method for representing the shape of the earth on a flat plane; a formula that converts latitude-longitude locations on the earth's spherical surface to X,Y locations on a maps flat surface. A system of intersecting lines, such as the grid of a map, on which part or all of the globe or another spherical surface is represented as a plane surface. The result may have distortion in distance, area, orientation and/or scale. See Conformal, Conic and Cylindrical Projections.

Prototype Model: Develop a test model to determine the feasibility of proposed data structures, software, hardware, communications, interfaces, and procedures. Typically involves the assembly of a very small geographic portion of the overall project area but the maximum range of data types and procedures anticipated in the development and operation of the ultimate geographic data model.



  1. Spatial index using regularly varying rectangular cell sizes. The cell area decreases as map feature density increase. Quadtrees are often used for storing raster data.
  2. Data structure for thematic information in a raster database that seeks to minimize data storage.
  3. One of a class of hierarchical data structures that facilitates encoding a grid or raster.

Query: A logical search specification finding spatial features with linked records that contain matching geographic and/or nongraphic attributes. A typical:

  • Spatial query is the comparison of XY coordinates of features/records with a user-defined spatial window (square, rectangle, circle, or multipoint polygon).
  • Logic query is a Boolean argument asking for various combinations of nongraphic attribute assignments.



  1. Images containing individual dots with color values, called cells (or pixels), arranged in a rectangular, evenly spaced array. Aerial photographs and satellite images are examples of raster images used in mapping.
  2. Method for storing spatial data that involves assigning a value to each dot in a large matrix. This method is very useful for modeling continuous phenomena like elevation of temperature.


  1. An assemblage of textural data withen a DBMS table and/or drawn statement as a means of preserving knowledge.
  2. Collected and preserved data describing a particular subject.
  3. A row (series of field values) in a database table. In a spatial database, each graphic feature may be linked to one or more records in one or more tables.
  4. A collection of fields or other sub-portion of computer file treated as a data unit.

Rectification: A set of techniques for removing data errors though calculation or adjustment. In image processing, computer programs that remove distortion within a digital image, aerial photography or remotely sensed data by removing parallax errors due to relief (high ground being closer to the camera than low lying areas), camera tilt, corner and other distortions.

Relate: To establish or demonstrate a connection between two or more things. In spatial analysis, establishing a temporary connection between records in two different tables using an item common to both. An indexing value in a field, both in the core table and the child table, that makes it possible to join the two so that they can operate as one combined table.

Relational Database: Information storage system in which there is an association between two or more things. Organized according to relationships between data items. Collection of tables that are logically associated to each other by shared common attributes. Entering the table name, attribute name, and the value of the primary key, any data element or set of elements can be retrieved. Consists of table rows and columns.

Relative Suitability: A DBMS query based on a scoring system that generates a relative suitability (multi-variable thematic) map. The technique involves:

  • Assigning raw scores to values within a DBMS field. For example rating a soil type as having a value of 4 on a scale of 10 regarding its development suitability; making the raw score of a parcel's land value equal to its land value.
  • Assigning relative importance values to a DBMS field.
  • Using values in each record to calculate a composite weighted raw score for each field involved.
  • Determining the number and limits of regime ranges.
  • Determining display parameters preparting relative suitability map (i.e. different colored pipes, roadway segments, parcel or intersected polygons as colored PLINEs, solid fills and/or hatch patterns).

Remote Sensing: Using a recording device not in physical contact with the surface being analyzed including:

  1. Using sensors sensitive to various bands of the electromagnetic spectrum.
  2. Assessing its spectral image without having the sensor in direct contact with the surface.
  3. Interpreting environmental conditions at, below and above the surface of the earth, typically by processing images from an aircraft (i.e. aerial photography), satellite imaging (ie. SPOT), or radar.

Resolution: Fineness of detail that can be distinguished in an image, as on a video display terminal.

  1. "Display Resolution" The density of the pixels that compose an image (See Pixels). The greater the number of pixels per square inch of screen, the greater the resolution. In print, resolution is measured in dots per inch (dpi).
  2. "Spatial Resolution" The smallest possible map feature that can be accurately displayed at a specified map scale. For example, in a 1:24000 scale map, a 50 foot distance between a roadway and railroad track centerline is one fortieth of an inch. Since the thinnest pen line width is presumed to be one fortieth of an inch, it is impossible to accurately represent the alignment of these two centerlines and still have a visible gap between them. To do this takes a smaller map scale (< 1:24000).

Rollback: Reversion of a DBMS record or digital map features to a previously assigned value. Changes made to the database in the last transaction are canceled.

Rubber Sheeting: Spatial database editing software that attempts to correct errors by stretching a map to fit known control points or monuments. Mathematical method to stretch or warp images to match existing vector data. Forces a digital map to fit a designated base. To implement, XY values of known coordinates within the survey control network are entered in conjunction with screen selections of the corresponding locations within the map overlay to be rubber sheeted. Each coordinate within the map overlay being processed is moved to the location of the prescribed control coordinate. A deformation (typically least square) algorithm is applied to translate, rotate, and/or rescale all other map features in a manner intended to minimize distortion.


Satellite Image: See Image and Image Processing. Land Records Glossary Page 6


  1. Relationship between the dimensions of a feature on a map and the geograhic features they represent on the earth, commonly expressed as a fraction. For example map scale of 1:24000 means that one unit of measure on the map equals 24000 of the same unit on the earth (1 inch would equal 24000 inches = 2000 feet).
  2. A calibrated line, as on a map or an architectural plan, indicating such a proportion.
  3. Description of how length in the real world is related to length on a map. This can be portrayed in a variety of ways including a representational fraction.


  1. In a textural database, organization of relationships within a database system including field names, header descriptions, size and type, and indexing configuations.
  2. In a spatial database, all of the above instructions needed to link attribute records to spatial features as well as other tables.
  3. In general, a set of organizational rules imposed on a body of data to assist in explaining its content and/or guiding response.

Screen Text: Text data actually visible on the display monitor. In nongraphic data, displays of text records, tabulations, and other text documents. In spatial database, text features used to annotate other map features such as road names, node numbers, pipe sizes and town names. In user interface, text visible in side, pull-down, pop-up, dialog and icon menus and picklists.

Scroll: To cause a spatial display to move vertically or horizontally across the screen so that a new line of text or graphics appears at one edge of the screen for each line that moves off the opposite edge.

SDTS: Acronym for Spatial Data Transfer Standard for transferring data between multiple geographic data management systems. Includes meta-data that addresses internal spatial reference, completeness, positional and attribute accuracy, logical consistency, completeness and data dictionary.

Sensitivity Analysis: Multiple scoring systems (See Relative Suitability above) are applied to a data model to generate multiple relative suitability maps, the scoring system for each being based on such "agendas" as:

  • Developers wanting minimum cost and maximum amenity.
  • Local community wanting minimum neighborhood impacts.
  • Environmental lobbies wanting minimum regional impacts.
  • Local governments wanting maximum tax revenues and minimum service obligations/ liabilities. Maps displaying best to worse relative suitability for each scoring system are generated and compared. With enough polygons, some will be allocated to the lowest or highest regime on all of them. Isolation of such areas serves as a starting point for building broad constituency to best-use recommendations.

Serial Communications: Digital transmissions in which information is transferred one bit at a time over a single wire or channel. In synchronous communications, blocks or packets of bits contain data are sent according to an established timing sequence. Serial lines are commonly use to connect peripheral devises to computer networks.

Site Selection: Process in which a variety of environmental, cost, and amenity factors are taken into account in attempting to identify which candidate site is the most suitable for the proposed land development or redevelopment. Can be as simple as quantitatively comparing the number of square feet of area that has both good soils and gentle slopes and as sophisticated as performing sensitivity analysis based on multiple agendas and dozens of spatial/environmental factors. (See Relative Suitability, Sensitivity Analysis).

Sliver Polygon:

  1. Gap between two lines created erroneously by a scanner and its raster-vector software.
  2. Refers to polygons formed when two adjacent polygons do not abut along a single common line resulting in the creation of a very thin polygon being present between the larger two.

Slope Analysis: Type of terrain analysis in which the change in elevation of the ground over distance is determined. Measured in terms of a ratio of rise or fall within a horizontal distance (run) expressed as decimal, fraction, percentage, or the tangent of the angle of inclination. Slope maps are depicted as a polygon overlay with each polygon geocoded according to the range of slope of the ground within its boundary. (i.e. 0-10%, 10-20%, etc.).

Smart CAD: CAD system that has the capability to link spatial elements with relational databases.

Snap: Radius used to eliminate gaps (undershoots) and dangles (overshoots) in boundaries as a preparatory step to building polygon topology. A distance parameter defining the maximum gap or dangle that will be adjusted. For example, if a snap radius of 2 is prescribed, all gaps and dangles greater than two model units in size will not be adjusted. Instead there locations will be marked for subsequent editing. Once all gaps and dangles are less than 2 model units, software "snaps" all end points of all contiguous polygon boundary segments to a single locations according to first-point-wins, averaging, and other algorithms.

Spatial analysis:

  1. Methods used to explore the spatial relationships between features both real and theoretical.
  2. Process of extracting or creating new information about a set of geographic features; techniques to determine the distribution of a spatial feature(s); and the relationships between two or more features, the location of, proximity to, and orientation of these features in space.
  3. Study of the locations and shapes of geographic features and the relationships between them.

Spatial Data: One of the three kinds of Data (spatial, textural and image). Spatial data is categorized according to the following feature types:

  • Zero dimensional features: Primitive Points; topological Node.
  • One dimensional features: Primitive Lines, Strings (multiple nonbranching lines), arcs (mathematically defined curve; topological Links, chains, and rings.
  • Two dimensional features: Polygons defining enclosed areas, Pixels, and Grid Cells.

Spatial Query: Function that allows a user to find, display, and/or isolate attributes records linked to map features located within a defined area of interest - window, circle, polygon or trace.

SQL: Accronym for Structured Query Language, a computer industry-standard syntax language for querying and manipulating most relational database management systems (DBMS). Commands can be embedded within a programming language to interface to a database or used interactively.

Staged Precision Strategy: Process whereby, as much as possible, cost of developing engineering-design precision for each spatial feature is distributed over time. Adequate survey control network for the entire project area is a mandatory requirement. Once in place, conversion of map documents into digital format is performed on a best fit basis. The first time that engineering precision is needed, a survey must be prepared that in turn must supercede the survey. Such precision enhancements are postponed, awaiting implementation of the following tasks/projects:

Land Transfer
Land Valuation.

State Plane Coordinate System: System of X,Y coordinates defined by the USGS for each state. Locations are based on the distance from an origin point defined for each state.

Surface: Boundary of a three-dimensional figure. Two-dimensional locus of points located in three-dimensional space. Set of continuous data in which there is an infinite set of values between any two locations. They can be built from regularly or irregularly spaced sample points on the surface.

Survey Control Network:

  1. Graphically defined lattice work of precise control points (monuments) and traverse alignments reconciled to those monuments, serving as a framework for referencing the position of all map features in the spatial database, thereby assuring appropriate precision standards.
  2. Points with a given horizontal position and surface elevation.
  3. Used to determine unknown horizontal positions and elevations of locations elsewhere in the active portion of the spatial database.

Synchronous: Data transmitted along a communication line in a continuous stream via serial or parallel lines according to an established timing sequence. Typically used in high speed local area networks (LANs) and mainframe computer configurations.


  1. Way of organizing information based on connections between member items.
  2. Combination of processes to handle and/or retain data.
  3. Group of related or interdependent equipment components configured to function as a unit.


TCP/IP: Acronym for Transmission Control Protocol/Internet Protocol, the standard for communication from one Internet computer to another.

Terminal: Device, often equipped with a keyboard and a video display, through which data or information can enter or leave a computer system.

Textural Data: One of the three kinds of data (spatial, textural and image).

Thematic Map: Representation of an area portraying how one or more real features or theoretical concepts are distributed.

  1. Displays a distribution of attributes. Typically a single variable (univariate) map such as soil or land use. Can also depict ranges of calculated values like:
    • Value category (i.e. 10-20% slope)
    • Density (10-20 persons per acre)
    • Relative suitability scores.
  2. Graphic display parameters typically include color assignment, solid fills, hatch patterns, symbols, and other graphic techniques.
  3. Uses information stored in a spreadsheet or database to create map displays for graphic presentations.

Thematic Precision: A much less stringent standard used to locate graphic feature needed to support multiple applications. (i.e. Land base that supports a management system, land use and/or infrastructure master plans, or environmental impact assessments. A recommended standard in this case would be all control points having an absolute accuracy of 5 feet or better and all referenced points having a relative accuracy of 20 feet or better.

Theme: Set of related geographic features, such as streets, parcels, or rivers, and the attributes (characteristics of those features). Geographic features logically organized into groups. Thematic map emphasizing a single environmental aspect such as soils, land cover, or geology.

Tiger: Acronym for Topologically Integrated Geographic Encoding and Referencing database standard developed by the U.S. Bureau of the Census to support the 1990 census.

  1. Supersedes the original DIME file standard that had been applied to only portions of the United States.
  2. Introduces political boundaries, feature names, and ZIP Code boundaries.
  3. Structured for easy implementation of standard address matching algorithems.

Tiled Mapping System: Part of a spatial database representing a discrete part of the earth's surface. By splitting (Tiling) a study area into tiles (sub-area facets), considerable savings in access times and improvements in spatial database management performance can be achieved. Needs only to access the data in a single modest sized map file to retrieve requested data (vs. a single very large file). Proceeds to access and retrieve data from other map facets as needed. Tiles are identical rectangular areas and/or arbitrary user determined size or shape, each with an associated spatial database file. Typically remembers which spatial file that a feature was retrieved from for archival purposes. Also uses the tile boundary to determine the storage location of a new feature according to the location of insert or start point.

Tiling: Data storage technique revolving around breaking up larger spatial areas into smaller areas or tiles. This technique typically speeds up manipulation of spatial databases.

TIN: Acronym for Triangulate Irregular Network, a representation of a plane surface as a grid of triangular polygons. These models can be built into hierarchical structures, and have a range of algorithms available for their formulation and translation to contour maps and surface grids.

Tolerance: Leeway for variation from a standard. Permissible deviation from a specified value of a structural dimension, often expressed as a percent. Parameter for defining a limiting distance for an operation. For example, a snap tolerance for 2 units apart means that any two endpoints less than 2 units apart will be moved to at a single point location.

Topographic Feature: Spatial representation of the surface features of a place or region on a map, indicating their relative positions and elevations.

Topology: Relationships between spatial features including such things as continuity, nearness, inside vs. outside, etc. Set of defined relationships between links, nodes, and centroids.

  1. Polygon Topology - representation of areas and area relationships using links and enclosed areas.
  2. Network Topology - representation of a linear network by links and nodes.

Transportation Network: System of interconnecting nodes and links that represent intersections of roadways, railroads, transit lines, or other forms of transportation systems. (See Intersection, Network Routing, Spatial Analysis, Utility Tracing).


Undershoot: Situation where a digital line does not meet up with its intended boundary line. The space between the two is called a gap.

Union: A set, every member of which is an element of one or another of two or more given sets.The combination of two spatial data sets where the result includes all of the features of the two inputs.

UNIX: Industry standard operating system (OS) developed as a joint venture between University of California at Berkeley and the AT&T Bell Laboratories. A multi-user multitasking OS operates on a wide variety of computer systems from micro to mainframe. Written in C, it carries with it C's inherent transportability that enables it to be easily ported to many different hardware platforms. In addition to their own proprietary operating system, many hardware venders offer UNIX as an auxiliary OS further expediting the free flow of data between multiple hardware platforms.

User Interface: Software components that expedite its intuitive and competent use. Options for command input by computer users rather than typing instructions at the command line. User interface can take on many forms including screen, pull-down and pop-up menus; icons, dialog buttons, toggles and picklists; toolbar buttons; printed tablet menus and cursor buttons on digitizing (mouse) devices. Also includes productivity enhancements, error messages, error trapping, on-line help, MACROS (and their prompts), sample databases, tutorials, manuals, and other documentation. See On-the-fly, Out-of-the-Box.

Utility Network: A network topology particularly well suited for simulating utility operations.

  1. Pressure (Looping) Networks. A non-branching utility network operation driven by position settings assigned to each end of each connecting Link. Typical pressure networks include gas, water and electric utilities.
  2. Gravity (Branching) Networks. Network database in which flow direction within a link is a determinate. All linear features are "drawn" according to their real world direction to better support gravity network simulation transactions. Pertains particularly to sewer, storm, telephone, cable, and some electric utility networks.


Valuation: A sub-set of a Computer-Aided-Mass-Appraisal System in the Assessor's Office.

Vector: Method for storing spatial data involving assigning coordinates for each entity.

  1. Mathematical object with precise direction and length but without specific location. Vector data is stored as XYZ coordinates that describe points, symbols, lines, areas, and volumes.
  2. Method for storing spatial data involving assigning coordinates for each entity; an X,Y,Z for a point, a pair of such points for a line, a series of such lines for a polygon, the method is very useful for modeling discrete physical features.
  3. Quantity, such as velocity, completely specified by a magnitude and a direction.

Viewer: A read-only stand-alone software system that supports the display, manipulation, and query of spatial databases. Commercial products that enable users reference and analyzed spatial databases prepared by a full function read-write product within the same product line. Typically has a user interface simpler than full function products. Supports rich command set but less than that available in the full function product. Easily programmable to expedite establishment of read-only application.

Viewshed Analysis: Analytical technique to determine the area of the earth's surface that can be viewed from a particular vantage point.

Virtual Map: Digital spatial database composed of multiple layers of specific area definitions, area boundaries, scale, features, related digital data files, and various other details selected as needed. Stored as a set of descriptive definitions that can be applied to create a map display on a pen plotter or an image on the screen along with nongrahic data and instructions linked to various and classes of map features.

Virtual Reality: Spatial computing environment that enables users to interface with a spatial database in an intensive manner. Goggles are placed in front of the eyes, each lens of which is a computer screen displaying a view of a shaded 3D spatial model (a building interior, urban plaza, a human knee joint, etc.) from a slightly different point of view. This displacement of viewpoints is equal to that between two human eyes making it possible to perceive the spatial model comparable to the way the real world is viewed. Sensors in the goggles manipulate the model display so that it reflects what is seen as the user turns his head or moves his body. In addition, a glove and/or other devises that respond to movements make it possible for the user to manipulate objects within this virtual reality. Potential and standard practical applications are being implemented in the space program, surgery, and industrial processes.


WAN: Acronym for a Wide Area Network that typically interconnects mainframe, mini-computers, and PCs providing communications links within areas larger than that served by a Local Area Network (LAN).


  1. Rectangular portion of a larger mapped area selected for display, for example, a rectangle surrounding Colorado and ignoring other areas in a databases covering the Western U.S.
  2. The defined outline of a section of an image which can be viewed simultaneously with other portions of the same or other images.
  3. In spatial queries, a type of boundary for creating a selection set of all spatial features and their linked DBMS records.
  4. A portion of the graphic user interface that enables you to open, close, resize, or relocate a rectangular area on the computer screen that is displaying information other than that being displayed by the spatial database (i.e. DBMS Table, edit, query, report display screens; documents in a word processor, image in a document management system).

World Wide Web: Part of the Internet that includes multimedia data. Many www pages include hypertext, which allow you to jump from one homepage to another by clicking on a highlighted word.




Z-Axis: Third or height axis of a three dimensional Cartesian coordinate system that crosses the XY axis plane at a 90 degree angle. The Z axis is normally used to represent elevation above sea level.

Zoom: Computer screen function to enlarge (zoom in) or decrease (zoom out) proportionately the size of the display features shown on the computer screen by rescaling the image. Common term in both CAD and GIS for changing the scale and or extents of a map. For example, "zooming in" shows more detail while "zooming out" shows less detail.

Zscale: A multiplier value greater than 1.0 that is used to define the vertical exaggeration of a 3D surface. The value is applied to all Z values of the points that make up the surface to make them appear more discernible and interesting.


Dan Anderson

Dan Anderson

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