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1)The closeness of an estimated (measured or computed) value to a standard or accepted value of a particular quantity, ie., relates to the quality of the result.
2)With regards to numbers in a mathematical table or those produced by a computer Accuracy may mean: (a) the number of significant digits in the numbers, (b) the order of magnitude of the least significant digit. ( See also Precision)
A set of rules for solving a problem. An algorithm must be specified before the rules can be written in a computer language.
A widely used industry standard code for exchanging alphanumeric codes in terms of bit-signatures.
An association formed by the American Government and industry to produce and disseminate widely used industrial standards.
A continuously varying electronic signal (contrast with Digital). Also refers to traditional paper mapping products and aerial photographs. p>
A set of computer programs designed for a specific task.
A line connecting a set of points that form one side of a polygon.
A fundamental unit of geographical information. See polygon.
Non-graphic information associated with a point, line, or area element in a GIS.
The process of drawing maps with the aid of computer driven display devices such as plotters and graphics screens. The term does not imply any information processing.
Computer-Aided Drafting (Design)
Relatedto records of land-related tenure, whether surface or sub-surface and whether linear, parcel-based or defined as a single point.
The basic element of spatial information in the raster (grid) description of spatial entities.
A sequence of coordinates defining a complex line or boundary. See Arc.
An alphabetical, numerical or special graphic symbol that is treated as a single unit of data.
A map consisting of areas of equal value separated by abrupt boundaries.
A graphic process of cutting lines and symbols off the edge of a display area.
A line connecting points of equal elevation.
A data model is an abstract representation of the data used by an organization, such that a meaningful interpretation of the data may be made by the model's readers. The data model may be at a conceptual, external or internal level (as defined by ANSI).
A set of computer programs for organizing the information in a database. Typically, a DBMS contains routines for data input, verification, storage, retrieval, and combination.
A collection of interrelated information, usually stored on some form of mass-storage system such as magnetic tape or disk. A GIS database includes data about the position and the attributes of geographical features that have been coded as points, lines, areas, pixels or grid cells.
A quantitative model of landform in digital form. Also digital terrain model (DTM).
The ability to represent data in discrete, quantized units or digits.
A device for entering the spatial coordinates of mapped features from a map or document to the computer.
The process of ensuring that detail along the edge of two adjacent map sheets matches correctly.
A fundamental geographical unit of information, such as a point, line, area, or pixel. May also be known as an entity.
A set of characters (alpha, alpha/numeric or numeric) within the GIS, which uniquely identifies a feature class or homogeneous group of features. The following examples are from the TRIM 1:20 000 Mapping Specifications: 33750000 - Wooded Area 25100190 - Paved Road 25000120 - Loose Surface Road (Gravel)
A collection of related information in a computer that can be accessed by a unique name. Files may be stored on tapes or disks.
In raster graphics, particularly image processing, a mathematically defined operation for removing long-range (high-pass) or short range (low-pass) variation. Used for removing unwanted components from a signal or spatial pattern.
Symbolism used for drawing a line or representing typefaces used for displaying text.
The way in which data are systematically arranged for storage in a computer and for transmission between computers, or between a computer and a device. Standard format systems are used for many purposes.
The scientific study of the size and shape of the earth and determination of positions on it.
A spatial framework of points whose position has been precisely determined on the surface of the earth.
A system of capturing, storing, checking, integrating, analyzing and displaying data about the earth that is spatially referenced. It is normally taken to include a spatially referenced data base and appropriate applications software.
The process of delimiting a given object, either physical (eg. a lake) or conceptual (eg. an administrative region), in terms of its spatial relationship to the land; the geographic reference thus established consists of points, lines, areas or volumes defined in terms of some coordinate system (usually latitude and longitude, or UTM northings and eastings, and elevation). The background framework pertinent to geo-referencing includes: NTS and BCGS grids and related features.
The activity of defining the position of geographical objects relative to a standard reference grid.
Represention of the earth's suface as a projection onto rectangular lines of latitude and longitude.
A system of earth satellites, each providing precise time and position information which enables a GPS receiver to compute the distance to each satellite. The distance measurements of at least three satellites are required to fix the receivers position in latitude and longitude. Measurements from a fourth satellite are required to provide vertical (altitude) positioning .
A small digitizer ( usually 28 cms x 28 cms) used for interactive work with a GIS or CAD/CAM system.
Levels of brightness (or darkness) for displaying information on monochrome display devices.
1. A network of uniformly spaced points or lines on the CRT for locating positions. 2. A set of regularly spaced sample points. 3. In cartography, an exact set of reference lines over the earth's surface. 4. In utility mapping, the distribution network of the utility resources, e.g. electricity or telephone lines.
A copy on paper of a graphics or map image originally displayed on a CRT.
The processing and interpretation of graphic images held in digital form.
A hardware component for data entry such as a digitizer, keyboard, scanner, tape drive.
To estimate the value of an attribute at an unsampled point from measurements made at surrounding sites.
A map displaying the distribution of an attribute in terms of lines connecting points of equal value; See contour, contrast with Choropleth map.
Jargon term for curved lines that have a saw-toothed appearance on a display device.
A tract of land, being all or part of a legal estate
The generic name for a series of earth resource scanning satellites launched by the United States of America.
The mode of holding rights in land.
Angular distance, expressed in degrees and minutes, along a meridian north or south of the equator.
The part of the drawn map explaining the meaning of the symbols used to code the depicted geographical elements.
The angular distance east or west from a standard meridian to another meridian on the earth's surface; expressed in degrees and minutes.
Land Information Infrastructure represents that physical infrastructure that will enable the Government to realize the data sharing and exchange objectives identified in CLISP. It establishes an overall target architecture which will integrate land-related data, application and supporting technologies within the Government.
One of the basic geographical elements, defined by at least two pairs of XY coordinates.
An array of data values that can be quickly accessed by a computer program to convert data from one form to another, e.g. from attribute values to colours.
Cartography; a hand-drawn or printed document describing the spatial distribution of geographical features in terms of a recognizable and agreed symbolism. Digital; the collection of digital information about a part of the earth's surface.
The process of reducing detail on a map as a consequence of reducing the map scale. The process can be semi-automated for certain kinds of data, such as topographical features, but requires more insight for thematic maps.
The basic system of coordinates used to describe the spatial distribution of elements in a GIS
The study of geometric properties and spatial relations unaffected by continuous change in the shape and size of figures.
Meta-data is data about data. It typically includes information such as currency, accuracy, extent, custodianship, and collection methodology. Meta-data is typically stored in data models, dictionaries, schemas and other representations.
1. The representation of the attributes of the earth Ās surface in a digital database. 2. The studying of landscape processes using mathematical algorithms written in computer code.
A modulator-demodulator device that allows data to be converted into a form whereby they can be transmitted as aset of pulses down a cable and then re-assembled at the other end.
A separate and distinct piece of hardware or software that can be connected with other modules to form a system.
A device, often carried in aeroplanes or satellites, for recording received radiation in several wavebands at the same time.
1. Two or more interconnected computer systems for implementation of specific functions. 2. A set of interconnected lines (arcs, chains, strings) defining the boundaries of polygons.
The point at which areas (lines, chains, strings) in a polygon network are joined. Nodes carry information about the topology of the polygons.
The process of stacking digital representations of various spatial data on top of each other so that each position in the areas covered can be analysed in terms of these data.
Hardware not part of the central computer e.g. digitizers and plotters
Contraction of picture element; smallest unit of information in a grid cell map or scanner image.
The technology used by an application. E.g. GIS platform is the GIS software and hardware being used.
A device for outputing hard-copy representations of data e.g maps p>
A multi-sided figure representing an area on a map.
A measure of the tendency of a set of random numbers to cluster about a number determined by the set. The usual measure is either the standard deviation with respect to the average ie., relates to the quality of the method by which the measurements were made and is distinguished from accuracy which relates to the quality of the result.
The representation on a plane surface of any part of the surface of the earth.
The process of converting an image made up of cells into one described by lines and polygons.
A regular grid of cells covering an area.
A set of attributes relating to a geographical entity; a set of related, contiguous data in a computer file.
The duplication of data in the database to improve the ease and speed of access to data, with the risk that changes may cause conflicting values.
An ellipsoid associated with a geodetic reference system or geodetic datum, whose surface is equi-potential and approximates the geoid in size and position. Reference ellipsoids are most commonly ellipsoids of revolution and are sometimes called reference spheroids.
A method of structuring data in the form of sets of records or tuples so that relations between different entities and attributes can be used for data access and transformation.
Relational Database Management System (see Database Management System and Relational Database)
The smallest spacing between two display elements; the smallest size of feature that can be mapped or sampled.
The transformation of spatial data to stretch or compress them to fit with other data
Spatial Archive and Interchange Format. SAIF is the Canadian Draft National Standard for Geomatics data interchange. Designed originally by the Government of British Columbia, it is a specification for data which includes an object-oriented data model and a language for describing both spatial and non-spatial data. Particular file or communications formats exist which are implementations of SAIF.
The relation between the size of an object on a map and its size in the real world.
A device for converting images from maps, photographs, or from part of the real world into digital form automatically.
A gap formed when two lines which should be contiguous are slightly separated in a graphical representation or map.
An earth resource satellite with high resolution sensors launched by France in January 1986.
The process of splitting an area into tiles.
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. Thematic information may be reprsented as labelled polygons. lines or points, chloropleth maps, isolines, etc.
A part of the database in a GIS representing a discrete part of the earth's surface. By splitting a study area into tiles, considerable savings in access times and improvements in system performance can be achieved.
A map showing natural and man-made features as well as relief, often in the form of contours.
The configuration of a planetary surface including its relief and the position of its natural and man made features.
The way in which geographical elements are related to each other. The topology of the data must be defined before GIS analysis can be performed.
The study of the place names of a region. A toponym is a place name.
The process of changing the scale, projection, or orientation of a mapped image.
A general-purpose, multi-user computer operating system. (known to its detractors as 'Eunuchs').
A means of coding line and area information in the form of units of data expressing magnitude, direction, and connectivity.
A usually rectangular area that is used to view or to transform the original map.
A capability for proportionately enlarging or reducing the scale of a figure or maps displayed on a CRT.