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Glossary of Terms and Terminology

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

R

Random Access Memory (RAM)

Volatile memory that loses information when power is lost. Compare with ROM. See also Main Memory

Raster

1. A regular grid of cells covering an area.

2. A pattern of scanning lines used for producing images.

Raster Data

Cell data arranged in a regular grid pattern in which each unit (or cell) in the grid is assigned an identifying value based on its characteristics.

Raster Database

A database containing all mapped, spatial information in the form of a regular grid of cells.

Raster Scan

A technique for generating or recording an image with an intensity controlled, line by line sweep across the entire display surface.

Read-only Memory (ROM)

Non volatile memory; i.e. that cannot be erased or destroyed by reading or by the removal of power. The information in the ROM can be read but not changed. (Compare with RAM)

Real Property Information

Any data that pertains to immovable property, especially land and buildings.

Real Time

Tasks or functions executed so rapidly that the user gets an impression of continuous visual feedbacks.

Record

A collection of fields.

Rectification

Process of removing the effects of tilt, relief, and other distortions from map data (or images).

Redundancy

The inclusion of duplicate data fields in a database.

Reference Ellipsoid

The mathematical model of the Earth used in geodetic computations. Synonym for spheroid, and ellipsoid. (See also North American Datum.)

Reformat

Procedure to change the data format to one usable by the system.

Region

1. A group of points or polygons that have a common attribute.

2. An area of the Earth's surface with one or more attributes that give it a measure of unity and uniqueness.

Registry Grantor/Grantee Index

A paper listing in the Registry of Deeds consisting of Document Grantor and Grantee names with Book/Page references. The Index is used as a search tool to access physical copies of registered documents stored in books in the Registry. This listing is produced on a periodic basis using information that is stored in electronic format for internal use and is maintained using a database application called DORIS.

Registry of Deeds

Offices established under the Registry Act to record, index and store copies of legal documents which deal with personal and real property.

Registry Plan Index

A paper lising in the Registry of Deeds consisting of plan reference information with registry Plan Numbers. The Index is used as a search tool to access physical copies of plans stored in cabinets or drawers in the Registry. This listing is produced on a periodic basis from information stored in a database taht is accessed and maintained by the Registry of Deeds using a database application called PlanLog.

Relation

See Table.

Relational Database Management System (RDBMS)

A database management system which performs its functions on the bases of relations between tables via indexing. Examples of RDBMS include: DB-2, Informix, Ingres, Oracle, Sybase, FoxPro

Relational Database Structure

Method of arranging information into sets so that relations between different sets can be used to provide access and transformation. (Compare with Heirarchical & Network)

Relational Join

An operation that combines two tables, both of which contain a column or a set of columns possessing domains common to both tables.

Relative Accuracy

Refers to the position of a feature in relation to its surrounding features. (See also Accuracy and Compare with Absolute Accuracy.)

Remote Sensing

Remote sensing is the science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with the object, area or phenomenon under investigation.

Repeatability

Ability to consistently obtain the same results when conducting the same operation.

Replacement Monument

A control point established to replace a destroyed monument [revised from submission by B. Fay]

Reporting Region

An aggregation of Nova Scotia counties into larger areas for the purpose of analysing government business and social outcomes. Delineation of the regional boundary would be dictated by the outer perimeter of each of the counties that comprise the region.

Resolution

(1) An indication of the number of component parts or units in a measurement system. When considering spatially referenced data, sometimes the number of units is normalized per unit area.

(2) The minimum size of a feature that can be reliably distinguished by a remote sensing system.

(3) Measure of the ability of a system to distinguish detail under certain specific conditions. The measure of this ability is normally expressed in lines per millimetre, meters per pixel, dots per inch, etc.

Resource Base Mapping

See Resource Mapping.

Resource Mapping

Topographic maps produced at a scale of 1:10000 or smaller. (Compare with Urban Mapping) (Also referred to as Resource Base Mapping.)

Response Time

Time that elapses between sending a command to a computer and the receipt of the results at a terminal.

Retrieval

The act of locating and providing on demand the information associated with a data item.

Ring Network

Computer communication network linked via a circular arrangement.

Rotation

Geometric transformation involving a change of orientation about a single point.

Row

An ordered collection of fields pertaining to an entity. A tuple in a relation.

Row Id

An integer that uniquely identifies each row in a table.

RS-232 Interface

An interface standard for connecting a peripheral device, such as a visual display unit or a printer, to a computer.

Rubberband

Ability to fix the ends of a line, or selected points along a line, in a static position and then "stretch" the line between the fixed points to establish new geometric shapes.

Rubber Sheeting

The fitting of slightly distorted data sets (e.g. air photos or map sheets) to a fixed mathematical model, such as a map projection.

Rule Base

One of the principal components of an expert system. The rule base contains knowledge that is procedural. It tells the computer how to manipulate data for the purpose of solving a problem. A rule may be represented as a conventional program.

Run Length Encoding

Simple data compression method that converts a run of identical data as a data followed by a count.

Run Time

The time during which a program is executed. Also known as Execution Time.

S

Scale

The ratio of the distance on a map, photograph, or image to the corresponding distance on the ground, all expressed in the same units.

Scale Bar

A pictorial representation showing relative distances on a map.

Scanner

A device for automatically converting images from maps, photographs, or from part of the real world into digital form.

Schema

A description (or picture or diagram) of the structures of an information system. There exist three data views (or schemata): External, Conceptual, or Internal.

Schema Table

A definition of the tables and their relationships within a data layer.

SCSI

(Pronounced scuzzy) Small Computer Systems Interface standard. An interface that permits daisy chaining of up to seven devices.

Scrubbing

See Cleaning.

SDTS

See Data Interchange Format.

Seamless Database

A database that provides the user with one continuous data structure, regardless of horizontal or vertical data partitioning. (Compare with Horizontal Seamless Database and Vertical Seamless Database.) Also called Continuous Database. (Compare with Cross-Tile Topology)

Seek Time

The time required to move the read/write head in a disk drive to the proper location on a disk.

Segmentation

Creation of new lines as a result of the fragmentation of an existing line.

Semantics

The implied meaning of data. Used to define what entities mean with respect to their roles in a system.

Sensor

Any device that gathers energy (e.g. electromagnetic energy), and converts it into a signal and presents it in a form suitable for obtaining information about an environment.

Sequential

Refers to data files in a serial order, that is, one file after another, usually stored on magnetic tape.

Sequential Access

Access to computer storage where information can be located only by a sequential search of the storage file.

Sequential Processing

Processing in the order in which items of information are stored or input. (Compare with Parallel Processing)

SIF

See Data Interchange Format.

Slivers

Refers to tiny polygons which are formed when the sides of two adjacent polygons do not match up. Often slivers are considered spurious in nature.

Slope

Rate of rise or fall of a quantity against horizontal distance expressed as a ratio, decimal, fraction, percentage, or the tangent of the angle of inclination. (Also called gradient.)

Smoothing

A set of procedures for removing short-range, erratic variations from lines, surfaces, or data series.

Snapping

The intersecting of disjoint lines.

Soft Copy

A non-permanent form of data output. This normally refers to the display of data on a Video Display Unit (VDU).

Software

General name for computer programs and programming languages.

Software Life Cycle

The stages that software undergoes consisting of the development stage and the almost perpetual maintenance stage.

Source

Information which describes the origin or derivation of a single feature, primitive, or attribute. It includes information about processing of the data as well as information about the data source.

Source Code

The untranslated code as written by a programmer.

Source Id

See Source Identifier.

Source Identifier

An alphanumeric code 12 characters in length, used to indicate the source of data or other information pertinenet to the data. (Also referred to as Source Id.)

Spaghetti Digitizing

Refers to the digitizing of map features (points and lines) without any regard to sequence or identification of line intersections.

SPANS GIS

See Geographic Information System.

SPANS Map

See Desktop Mapping Software.

Spatial

Of or pertaining to space; occupying space; occurring in or conditioned by, space; considered with relation to space; having the character of space.

Spatial Analysis

Analytical techniques associated with the study of the location of geographic entities together with their spatial dimensions.

Spatial Archive and Interchange Format (SAIF)

A data exchange standard based on a multilevel, modular design. (See also Data Interchange Format)

Spatial Completeness

The degree to which geographic data covers a geographic region. (Compare with Content Completeness.)

Spatial Data

1. See Spatial Representation.

2. Data pertaining to the location of geographical entities together with their spatial dimensions. (Synonomous with Geographic Data)

Spatial Index

A data structure file that allows for the rapid identification of a primitive by using the values of the primitive's coordinates.

Spatial Interpolation

The capability to interpret proportions between points of known elevation for the purposes of establishing contours or elevation values between these points.

Spatial Object

Anything which is fixed in or occupies space.

Spatial Query

Allows the extraction of cartographic data based on user-defined windows, such as a circle, or other regular and irregular shapes.

Spatial Reference System

A coordinate system based upon survey measurements used to define the relative and/or absolute location of features.

Spatial Relationship

An association of two or more elements in some dimension of space.

Spatial Representation

The combination of a set of spatial elements and their associated spatial references. A spatial element is an object whose definition is directly depenent on the background framework pertinent to geo-referencing. Non-spatial elements that are referenced through and dependent on their association with spatial elements are said to be explicitly referenced via the spatial representation, while non-spatial objects that simply maintain a reference to the spatial elements are said to be implicitly referenced via the spatial representation.

Spike

1. An overshoot line created by a scanner and its raster-vector software.

2. An anomalous data point that protrudes above or below an interpolated surface representing the distribution of the value of an attribute over an area.

Spline

A mathematical curve used to represent spatial variations smoothly. (See also Line Smoothing)

Spot Height

An elevation read and displayed at a location suitable for cartographic purposes.

Standards

Specifications which describe a dataset (conventional or digital) commonly employed by one or more user group outside the agency or department which provides that dataset.

Start Node

The first node of an arc.

Stereo Plotter

A device for extracting information about land forms from stereoscopic aerial photographs. The results are sets of X,Y and, in many cases, Z coordinates if equipped with digital encoders; or a paper plotter if equipped with a pantograph.

Stereo Model

The area of overlap between two successive aerial photographs. Also referred to as Model.

Storage

Any physical device in or on which computer data can be kept. (For example: RAM, ROM, Disks, Tapes, Optical, etc.)

Street Network File (SNF)

See AMF.

String/String Variable

Information consisting of both letters and numbers, and possibly including other symbols such as punctuation marks and mathematical symbols.

Structured Query Language (SQL)

A database sublanguage used in querying, updating, and managing relational databases.

Stylus

A graphic data input device that looks like a pen.

Sun Shading

DTM display technique where slopes are shaded as if they were illuminated by a light source.

Surface

A level of spatial measurement referring to a three-dimensional defined space. Examples include contours, isolines, bathymetry, etc.

Surface Mapping

The display of three dimensional information in terms of 2-D formats, either through contour mapping of 3-D displays, or colour, shading, hatching or other techniques.

Survey, Mapping and Remote Sensing Sector (SMRSS)

See Geomatics Canada.

Sybase

See Relational Database Management System.

Symbol File

A digital reference file used by digital mapping applications, which contains graphic representations of various geographic entities and possibly including font definitions.

Symbology

Conventional language of presentation of cartographic features.

Syntax

A set of rules governing the way statements can be used in a computer language. (See also Data Syntax)

System

1. A structured organization of people, theories, methods, or equipment.

2. A computer.

3. A network of computers.

System Architecture

Overall configuration and design of a system from data structures to operating procedures.

T

Table

An organizational structure for data content. In the relational model, a table is a group of repeating rows defined by columns. Equivalent to a relation. (Also referred to as Relation.) (See also Flat File)

Tabular Data

Data in a row and column format.

TCP/IP

Transport Control Protocol/Internal Protocol. The specified US Dept. of Defence ARPA Network protocol implementation for Layers 3 and 4 of the OSI reference model.

Terabyte

1024 Gigabytes.

Terminal

1. Dumb - a computer terminal that does nothing more then pass data to and from the processing unit, over some type of communication lines.

2. Intelligent - A display terminal, also called a programmable terminal, that has substantial processing capabilities, and can be used for extensive data editing.

3. Workstation - A personal computer or terminal connected to a local area network. See also Workstation.

4. A device, usually including a CRT and a keyboard, for communicating with a computer.

Terrain

Surface of the Earth.

Terrain Analysis

Analytical techniques to determine the effect of terrain on a particular operation. Usually involves slope, soil types, and vegetation.

Tessellation

Process of splitting an area into tiles.

Text Editor

A software program for creating and modifying text files (normally ASCII).

Text Feature

A cartographic entity that relates a textual description to a zero- or one-dimensional location. A text feature usually contains information such as font, colour, and height.

Text Primitive

Characters placed in specific locations in a coordinate system. Text is a cartographic object, rather than a geographic entity, since it does not participate in topology. A text array indicates a variable-length collection of characters. (Also referred to as Cartographic Primitive.)

Thematic Databases

Databases within the provincial land information system containing information pertaining to the class characteristics of particular spatial variables. Examples of thematic databases are Forestry, Minerals, Agriculture, Soils. (Compare with Primary Databases)

Thematic Map

A map displaying selected kinds of information relating to specific themes, such as soil, land-use, population density, suitability for arable crops, and so on.

Theme

See Data Layer.

Theme Number

A number assigned by some GIS's to a set of grouped features. This number is used to 'layer' digital data. (Also referred to as User Number.)

Thinning

Process whereby a linear feature is generalized through the use of a series of rules that reduces the number of data points while maintaining the basic shape of the feature. (Also referred to as Weeding.) (See also generalize)

Third Generation Language (3GL)

COBOL, FORTRAN. (See also Programming Language)

Three-dimensional Data

1. Volumetric data representing measurements in three dimensions, as angular or linear measures such as phi-lambda-kappa or latitude-longitude-elevation.

2. Data containing X,Y and Z coordinates.

TIFF

A raster data format developed and standardized by Aldus Corp. and Microsoft Corp. It allows images to be compressed in any of six different formats, including uncompressed, three versions of runlength encoding, two versions of two-dimensional encoding and an LZW format, which is currently the most popular method for compressing colour and gray-scale images.

Tile

A spatial partition of a data layer that shares the same set of feature classes with the same definitions as the data layer. The topology of each tile is independent of that of each other tile in the data layer. (See also Management Unit)

Tiling Scheme

The scheme used to define tile shape and size and to identify tiles (assign identification numbers).

Time Sharing

The use of a common CPU by several users in such a way that each user should be able to feel that he or she has the whole computer to themselves.

Title

The evidence of right which a person has to the possession of property.

Topo Base

See Topographic Database.

Topo Database

See Topographic Database.

Topo Files

See Topographic Database.

Topographic Analysis

Analysis of the configuration of a surface, including its relief and the position of streams, roads, cities, etc. Usually subdivided into hypsography (the relief features), hydrography (the water and drainage features), cultural (manmade features), and vegetation.

Topographic Database

The set of models or digital topographic files compiled from overlapping aerial photographs. (Also referred to as Topo Base, and Topo Database.)

Topographic Feature

Topographic phenomenon describing planimetry and/or altimetry (terrain relief).

Topographic File

A subset of a model that is bounded by points chosen to ensure complete stereo coverage of the area being mapped. Current procedures eliminate data redundancy between adjacent topographic files. (Also referred to as Topo File.)

Topographic Map

A map showing correct horizontal and vertical positions of features such as roads, structures, water courses, and contours. (Compare with Planimetric Map.)

Topography

The configuration of a planetary surface including its relief and the position of its natural and man made features.

Topological

Refers to such properties of geometric figures as adjacency that are not altered by distortion as long as the surface is not torn.

Topological Error Checking

Process of ensuring that the logical consistency of the data is intact for network topolog, or polygon topology as appropriate.

Topologically Clean Data

Data which have been processed through topological error checking procedures and then through procedures to remove topological errors in a continuous loop until no errors remain in the data. Topologically clean data (aka GISable data) may be moved from one GIS to another, either by direct translation or by means of an interchange format mutually recognized by each GIS. Once translated into the native file structure of the receiving GIS, all of the same topologcial relations between graphic data elements possible in the originating GIS can be built without error in the receiving GIS. In addition, any keys linking the data elements to attribute data are provided in the data such that any links to attributes for any graphic elements which were possible in the originating GIS may be established in the receiving GIS. A given collection of data may contain topologically clean sub-sets as well as other data which needs to be exempted from a topological building process.

Topologically Integrated Geographic Encoding and Referencing (TIGER)

U.S. Census Bureau reference files developed for the 1990 Census. Similar to the DIME files, TIGER was developed as a tool for assigning census data collected by addresses, to various geographic areas such as tracts and blocks.

Topological Structuring

Process of organizing data topologically so that the relationships and reference linkages are specified. Topological structuring in a GIS is normally built within the native file structure of that particular GIS; however, with topologically clean data, exactly the same relations can be built in another GIS

Topological Verification

See Topological Error Checking.

Topology

1. Explicit coding of spatial relationships between map elements. Spatial data are classified as point, line, area, or surface or in the topological sense - nodes, arcs or polygons.

2. A branch of geometrical mathematics which is concerned with order, contiguity, and relative position, rather than actual linear dimensions and with geometric relationships that are unaltered by distortion. (See also Database Topology, Network Topology, Polygon Topology.)

Toponymy

Geographic names. (e.g. cities, rivers, etc.)

Tracker Ball

An interactive, hand-controlled device for positioning the cursor on a CRT.

Transform

The process of changing the scale, projection, or orientation of a mapped image.

Traverse Data

Data relating to a survey made using a method whereby lengths and directions of lines between points on the Earth are obtained by or from field measurements, and used in determining position of the points.

Triangulated Irregular Network (TIN)

A data structure which describes a three-dimensional surface as a series of irregularly shaped triangles. Usually used in connection with terrain modelling.

Tuple

A set of values or attributes pertaining to a given item in a database. Also known as a record. (See also Coordinate Tuple)

Turn-Key System

A GIS or CAD/CAM system of hardware and software that is designed, supplied, and supported by a single contractor ready for use for a given class of work.

U

Undo

Refers to the ability to retract a previous entry or command.

Undershoot

See Gap

Union

The result of merging data or data points.

Universal Transverse Mercator Projection (UTM)

A common rectangular.(Cartesian) coordinate system based on projection of locations on the Earth onto a cylindrical surface. Coordinates are usually expressed in meters north (northings) and meters east (eastings) from reference axes that define a given zone. (See also Map Projection)

UNIX

A modern, general purpose operating system produced by Bell Laboratories. It provides a simple, uniform environment that allows a number of users to operate on a single system. (See also Operating System)

Updating

Process of changing the graphic characteristics or attributes of a feature.

Upload

The transfer of data or programs from a remote location to central computer.

Urban Mapping

Topographic maps produced at scales larger than 1:10000 (Compare with Resource Mapping.) (Also referred to as Urban Topo Mapping.)

Urban Topo Mapping

See Urban Mapping.

User

A person, or organization that uses a system.

User Friendly

A qualitative term that is applied to computers which are easy to operate and provide assistance (responses) when prompted for help. They allow communication in high level programming languages and/or natural languages.

User Interface

Method by which the human operator communicates with the various data base and applications modules.

User Number

See Theme Number.

User Requirement Analysis

Study of the needs of potential system users.

Utility Programs

A library of programs that provide for a number of general operations such as edit and delete.

V

Variable

A named storage location capable of containing a certain type of data that can be modified during program execution. (Compare with Parameter)

Variable-length Column

A column whose length is determined by the amount of storage needed to store its contents. Useful for character strings and coordinate strings.

Vector

1. Indicates a collection of coordinate tuples to define a geographic or geometric entity.

2. Distance quantity having both magnitude and direction. In most GIS cases it is represented as an ordered pair of points.

Vector Data

Data comprised of x,y coordinate representations of locations on the earth, taking the form of single points, strings of points, or closed lines

Vector Data Structure

A term describing a class of spatial data structures in which spatial information is represented as vectors.

Vertex

Geometric representation of the beginning or end of a line or of the intersection of two consecutive segments composing the line. It is defined by its coordinates.

Vertical Seamless Database

A series of hierarchical databases that provides the user with the perspective of one continuous data structure as they move from one scale of data to the next. (Compare with Horizontal Seamless Database and Seamless Database.)

Vertical Distance

See Orthometric Elevation

Vertical Exaggeration

A constant value used to multiply Z values in a DEM for realistic perspective viewing.

Viewshed

Spatial data displayed to represent a given perspective.

Viewshed Analysis

The capability of calculating and displaying the land site across the top of a reference surface for one or more selected view points. (See also Line-of-sight Analysis.)

Virtual Line

A line created and used solely to add logic to the data.

Virtual Memory

Memory which can appear to programs to be larger than it really is because blocks of data are rapidly moved to or from secondary storage when needed.

VMS

See Operating System.

W

Weeding

See Thinning.

Window

1. Rectangular frame with a specified size and location on the screen of an interactive graphics system, and within which a rectangular portion, or window, of the map is displayed.

2. Geographic area defined by some criteria for the collection, analysis or display of spatial data (See also Management Unit.)

Write Once, Read Many (WORM)

Information recorded on a WORM disk can neither be erased nor re-recorded.

Word

A set of bits (typically 16 or 32) that occupies a single storage location and is treated by the computer as a unit of information.

Workstation

Single user computer station designed for high performance graphic and numerical computations. (See also Terminal definition 3)

X
Y
Z

Zoom

A capability for proportionately enlarging or reducing the scale of a large figure or maps displayed on a CRT.

Z-value data points

Data points providing a value perpendicular or normal to a specified surface (May be synonomous with Orthometric Elevation), or in a true 3-d coordinate system, the value which provides the third dimension.

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