H

hardware

Physical components of a system. 

heads-up digitizing

Also called on-screen digitizing. Refers to the digitizing (in effect vectorization) of scanned images displayed on the screen. User specifies points, lines, and areas by means of the screen cursor. This technique means that a digitizing table is not required. It can be as accurate, or even more accurate, than table digitizing. 

hierarchical database structure

Arranging of information in a database such that data is connected by a hierarchical defined path, from the top going down. The relations in this structure are one-to-many. 

hill shading

See sun shading 

histogram

Diagram or image showing frequency distribution -- shows number of values which fall into contiguously defined classes (value ranges). 

HPGL

Hewlett Packard Graphics Language. HPGL is a graphics format designed to generate plotter output. Is supported by many vendors. 

hue -- graphics

Particular shade or tint of a given colour. 

hydrography

Surveying, charting, and mapping of bodies of water -- oceans and seas. 

hydrology

Primarily the study of water on the surface of the earth -- lakes, streams, rivers, ground water. 

HYLAM

Hydrographic LAndscape Model. Model for recording and storing hydrographic data. 

HYPREM

HYdrographic PREsentation Model. Model for presenting and displaying HYLAM-data on different presentation media. 

hypsometry

Refers to measuring surface elevation relative to sea level. 

I

icon

Graphical representation of an object -- this might be a data file or a disk drive. Icons are used to interact with and control computer system functions. 

IGES

Initial Graphics Exchange Specification. Developed as a neutral format for the transmission of computer representations of engineering drawings between dissimilar CAD/CAM systems. 

image processing

Techniques and procedures dealing with the acquisition, analysis, and output of digital images. 

imagery

Visual representation of features recorded by cameras on film or by sensing devices with information stored and displayed digitally. 

imaging

Recording of graphic images, either digitally or on film. 

import

The process of bringing in (and usually transforming) data from another system. 

index map

Reference map sheet which outlines a mapping area and identifies all map sheets or sub-map sheets required to see the entire mapping area in detail. 

inset map

Enlargement of a overly detailed portion of a map -- will appear on the same map sheet or a separate map sheet. 

interactive

System mode of operation where the user can input information and initiate or modify program execution by means of an input device (terminal) and receive information from the system regarding progress, performance, errors, etc. 

interface

Connection between two devices or things. Interface can refer to connections between hardware, software, or between people and computers. 

International Organization for Standardization (ISO)

International standards organization involved with setting of standards on a world-wide basis. ISO is made up of national standards organizations from more than 75 countries. 

interpolation

Determining the value at an unsampled location based on the value of sampled locations. 

ISIF

Intergraph Standard Interchange Format. Digital graphics exchange format implemented and promoted by Intergraph Corporation for the import and export of CADD/CAM and related data to and from Intergraph graphics based systems. ISIF supports both ASCII and binary exchange formats. A number of other vendors also support ISIF or portions of ISIF for data exchange purposes. 

island

Polygon which is "completely" enclosed on all sides by another larger polygon. The larger polygon is sometimes referred to as a lake. 

ISO

See International Organization for Standardization 

iso-

Prefix used to describe a variety of lines on a map connecting points of equal value. E.g., isobar -- equal pressure; isotherm -- equal temperature. All of these may be considered isolines. See isoline 

isobath

Contour lines showing the bottom of a body of water. 

isoline

Line connecting points with equal value or common characteristics (e.g., rainfall intensity, temperature, barometric pressure, etc.). Displayed isolines are referred to as an isopleth map. 

isoline map

See isopleth map 

isometric view -- graphics

View of a 3D object which shows all three dimensions in equal proportion -- is not true perspective. 

isopleth map

Map showing distribution of values using isolines. 

isotropic surface

Uniform, featureless surface. 

J

jaggies -- graphics

Refers to alias effect. See alias 

join -- as a process

Action or process of connecting together two or more separately digitized maps. 

join area

Area where two or more adjacent coverages are brought together to form one continuous larger coverage. 

K

K

Abbreviation for kilo. See kilo 

kilo

Typically used to mean 1000. In computer applications it stands for 1024. 

knot

See NODE 

kriging

Method of interpolating point data to a grid. Uses statistical theory and a multi-step approach. 

L

label

Descriptive information related to a graphic object. Labels are distinguished from annotation, in that labels are part of the attribute data base while annotation is strictly related to graphic display. 

LAN

See local area network 

land information system

See geographic information system

land related data

Data that is referenced, in some way, to a location on the earth's surface. 

land related information system

See geographic information system

land use

Refers to the use of land (often the category of use) by humans. 

latitude

Angular distance north or south of the equator. Measured and indicated in degrees, minutes, and seconds. 

layer(s)

Refers to a set or grouping of data which may be treated as an "overlay". Each set of data usually deals with one topic or theme (e.g., rivers, roads, forest type) and each "overlay" is related to each other by a common coordinate system. 

leaking polygons

Polygons which are not totally closed. Leaking polygons constitute a topological error and it is desirable that a GIS have some mechanism to detect this condition. 

legend

Is an explanation of symbols and other information shown on a map. Usually the legend appears as a table or list in the map's margin (to the side or bottom). 

level slicing -- raster

As raster operation -- extraction of pixels from an image according to their value. 

light bar

Refers to the use of colour or reverse video to highlight an option appearing on the display screen (e.g., a menu choice). 

line

Basic unit of geographical information (having length and direction) defined by two or more pairs of X,Y coordinates. All linear features are built up of line segments. 

line break

Process of breaking a line into two parts by inserting a new node. 

line of sight display

Display (given a DTM) showing what would be visible from a given point along a specified line or view direction. 

line snapping

Automatic or interactive "connecting" of line endpoints separated by less than some "tolerance" distance. The tolerance may be set by the user or may be a fraction of the map extent. 

line thinning

See weeding 

LIS

Land Information System. See geographic information system 

local area network

Communications network connecting several users and devices in a confined geographic area (usually an office or building). 

log/recording facilities

Ability of the computer system to automatically record user activities performed on the system. Able to produce statistics about operations taking place. 

longitude

Angular distance east or west of the Greenwich meridian. Measured in degrees, minutes, and seconds. 

LRIS

Land Related Information System. See geographic information system 

M

macro

Set of frequently used operations (combined together to form a script) which can be executed by a single command. 

macro processor

Software that executes (and possibly allows for the creation) of a macro. 

macro programming language

Relatively simple language allowing the user to manipulate and control commands and create macros for subsequent execution. 

map

Representation of the earth's surface (usually in part) on a flat surface at a given scale. Maps are traditionally produced on paper. 

map extent

Area of the real world which is represented by the map. In GIS it is usually defined by the smallest non-rotated bounding rectangle which contains all of the map features. 

map projection

See projections 

matrix

An array of rows and columns. May be greater than 2D. 

MB

Abbreviation for megabyte. 

Mb

Abbreviation for megabit. 

measurement -- area

Calculation of the area of a polygon feature. 

measurement -- distance along

Calculation of distance along a linear (or curvilinear) feature. 

measurement -- distance to

Calculation of surface distance between two features on the coverage (either point-to-point or point-to-line). 

measurement -- perimeter

Calculation of the perimeter of a polygon feature. 

media

Plural for medium. Refers to the actual physical device used to store data on.  

meg

Abbreviation/slang for mega -- one million. 

mega

In general means one million (in precise computer terms is 1,048,576). 

menu

Display of functions or options available. On a display screen this can take the form of tables, side bars or lines at the bottom/upper part of the screen. On a digitizing table, it consists of a document (either in a fixed or user specified location) illustrating the various commands. 

menu-driven

Program/system which is operated by selecting options from a menu. 

meridian

Great circle passing through the geographical poles and a given point on the earth's surface. 

mini-topo

Potential format being developed by the Defense Mapping Agency (DMA) in the United States for the distribution of portions of their data. 

MIS

See management information system 

model

Representation of reality (the real world) which can be displayed, analyzed, and manipulated. 

modeling

Process of building a model (abstraction of reality). 

MOEP-STF

(British Columbia) Ministry Of Environment and Parks - Spatial Transfer Format. The MOEP format is an enhancement of the DMDF format developed by the Province of Alberta. This format is primarily intended for the exchange of 1:20,000 digital topographic and cadastral data. 

morphological map

Map depicting detailed surface forms. 

mosaic

Result of assembling and matching adjacent images to form a larger continuous image or representation. 

mosaicing -- vector

As a vector operation -- joining of two or more adjacent coverages into one. The production of a composite map. 

multiple seed points

Multiple identification points for a polygon. This condition should be considered a topological error and be flagged by a GIS. 

N

NAD27

1927 North American Datum. Most North American surveys are relative to this geodetic datum. 

NAD83

1983 North American Datum. With better technology, survey accuracy has increased significantly over the past few decades. As such, it has been proposed that survey control positioning be relative to NAD83 geodetic datum -- which is more accurate than NAD27. There can be significant impacts to organizations regarding the change from NAD27 to NAD83. 

neatline

Surrounding border line containing all of the cartographic elements on a map. Is considered a cartographic enhancement. 

network

System of interconnected links or lines. 

network analysis/modeling

Ability of a GIS to perform various routing or path analysis operations. Common operations are: time and/or distance flow analysis, facilities siting, and selection of optimum route. 

network database structure

Refers to the arranging information in a database such that there exists explicit connections and relations defined by links or pointers. The relations in this structure are one-to-many (some very general definitions may use many-to-many). A directed graph model can be used for this structure. 

network structure -- gis

Within a GIS, this indicates that arcs, nodes, and polygons are stored in a network or directed graph structure. This has importance since such a structure can facilitate other operations (e.g., network modeling). 

neutral format -- data exchange

Data exchange approach where data on one system is converted to a format independent of either system, then converted to the format of the second system. This contrasts with direct conversion where a translator converts data from one system's format directly to the other's. 

node

Special kind of point where lines (arcs, strings, chains) meet. Also known as Knot. Nodes are used to help define topology. 

nominal geocoding

Process of geocoding but to a nominal or relatively low level of accuracy. Addresses and postal mailing codes are examples of nominal geocoding. 

O

object

Digital representation of a spatial entity (in part or in total). 

on-line

Peripheral device (plotter, printer, etc.) which is turned on and ready to operate or function. 

on-line help

Ability to access instructions (receive help) on commands and procedures via the computer operating system or GIS. 

optical tape

Blending of optical and tape technology. Can be used to store a full terrabyte of data. 

orthophotograph

Aerial photograph having properties of an orthographic projection. Orthophotograph is derived from a regular photograph that has been processed to have displacement and distortion removed (caused by camera tilt and terrain). Orthophotographic map is a mosaic of orthophotographs all at the same scale. 

orthophotoquad

Orthophotographic map with contours and cartographic enhancement. 

outline map

Map showing only the extent and divisions within a region. 

overlay -- graphic

Visual display only. Consists of separate images being simultaneously displayed, one on top of the other. 

overlay -- raster -- algebraic

Operation on raster data where the value of a pixel output is the result of an "algebraic" calculation performed on the input pixels all occupying the same spatial location. 

overlay -- raster -- logical

Operation on raster data where the value of a pixel output is the result of a "logical" calculation performed on the input pixels all occupying the same spatial location. 

overlay -- vector operation

Compilation of a coverage whose elements are a function of an operation (e.g., polygon on polygon) and of the content of the input coverages. A GIS should be able to perform overlay operations on point, line, and polygon coverage (or their combinations) and reconstruct topology where appropriate. Some types of overlay operations are: point in polygon, line in polygon, etc. 

 

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