Glossary
Address Matching
A mechanism for relating two files using an address as the related item. Geographic coordinates and attributes can be transferred from one address to the other. For example, a data file containing student addresses can be matched to a street coverage that contains addresses creating a point coverage of where the students live.
Aerial Triangulation
The process of controlling overlapping aerial photographs so they can be used for compiling features and extracting elevation data using analytical or softcopy plotters (see Stereo Data Capture). Because the controlled photos are linked to a ground control points, they can be rectified to produce orthophotos.
Aerial Photograph
A photo that is taken from the air. Aerial photographs that are used for aerial triangulation are taken by special cameras that can be calibrated to a high degree of accuracy, and are usually taken of the land directly below the plane.
Aeronautical Charting
Aeronautical charts are specialised maps used in aerial navigation. Terralink produces Aeronautical charts under contract for Airways Corporation New Zealand Ltd.
ArcInfo
Desktop GIS software package written and marketed by Environmental Systems Research Institute (ESRI). Developed into ArcView.
ArcView
Desktop GIS software package written and marketed by Environmental Systems Research Institute (ESRI). Cheaper and easier to use than their original system ArcInfo, ArcView has become well-established as one of the world's most popular desktop mapping packages. Windows based user interface means that novice users can be quickly taught to manipulate analysis and graphical tools. Can be linked to ArcInfo database files and can handle both vector and raster data types through the addition of extensions.
Attribute
Non-graphic or descriptive information associated with a geographical feature (point, line, area) in a GIS.
Base Map
A set of topographic data displayed in map form providing a frame of reference or contextual information to the user.
CASE
Computer-Aided Software Engineering. CASE tools are defined programming rules for applying engineering principles, methods, techniques, and concepts. These tools assist in accomplishing a definable engineering task in the software design process by automating manual activities through structured prototyping. This technique reduces customised development time, supplying consistent code sets and supporting the entire software life cycle process.
CAD
Computer Aided Design or Computer Aided Drafting.
Cadastre
A public register or survey that defines or re-establishes boundaries of public and/or private land for purposes of ownership and/or taxation.
Chart
A map used for nautical or aeronautical navigation.
Control Points
A system of points with established horizontal and vertical positions which are used as fixed references in positioning and relating map features, aerial photographs or remotely sensed images.
CRS
Core Record System. The system developed by LINZ as the new title and survey information database. It replaces the DCDB.
Cultural Features
Items in a spatial database representing man-made objects.
Data Capture
Encoding data into a digital or computer-compatible format. This includes digitising, direct recording by electronic survey instruments, and the encoding of text and attributes. Can also refer to Stereo
Data Conversion
Altering or changing data. This can include translating it into a different format, taking out extraneous data, and restructuring data.
Data Modelling
A Data Model is a description of the relationships between different entities.
Datum
Any point, line, or surface used as a reference for a measurement of another quantity.
A model of the earth used for Geodetic calculations.
DCDB
Digital Cadastral Database. This database records cadastral data. It is being replaced with the CRS.
DEM
Digital Elevation Model.
Diapositive (Diap)
A positive photograph image on a transparent medium that is used in stereoplotting instruments.
Digitising
An automated or manual process of converting information in analogue form (such as a photograph or hard-copy map) into digital form.
Draping
The display of selected two-dimensional data on a perspective view of terrain relief or any other spatially distributed variable. For example: displaying land cover information on a DEM.
DTM
Digital Terrain Model.
Elevation
A vertical distance below or above a reference surface (usually mean sea level).
Entity
In cartography, a real world object that cannot be further subdivided into similar objects, for example a road, or a building.
In relational databases, an entity is an object and its associated attributes.
ESRI
Environmental Systems Research Institute (ESRI).
Feature
A set of points, lines or polygons in a spatial database that represent a real-world entity. The terms feature and object are often used synonymously.
Geocoding
Process of assigning geographic locations (including addresses) to objects relative to a standard reference grid (co-ordinate system).
Geodesy
The scientific study of the size and shape of the earth and determination of positions on it.
Geodetic Datum
Any point, line, or surface used as a reference for a measurement of another quantity.
A model of the earth used for Geodetic calculations. A model of the earth's shape.
Georeferencing
The process of delimiting a given object, either physical (e.g. a lake) or conceptual (e.g. 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).
To establish the relationship between page co-ordinates on a planar map and known real-world co-ordinates, e.g. connecting an orthophoto to the ground co-ordinate system.
GIS
Geographic Information System.
GPS
Global Positioning System. A system of satellites and receiving devices used to compute positions on the Earth. GPS is used in navigation, and its precision supports cadastral surveying.
Graticule
The depiction of the lines of latitude and longitude on a map. The network of parallels and meridians plotted on the map in map projection. The lines will not be orthogonal or even, in general, straight.
Ground Point Control
Any point which is recognisable on both remotely sensed images, maps and aerial photographs and which can be accurately located on each of these. This can then be used as a means of reference between maps or, more commonly, between maps and digital images. Often used in registering remotely sensed images and surveying.
Index Contour Line
A contour line that is labelled with a value.
Intermediate Contour Line
An unlabelled contour line.
Interpolate
To estimate the value of an attribute at an unsampled point from measurements made at surrounding sites. Often used to estimate the elevation of points in a DEM.
ISO
International Organisation for Standardisation. A worldwide federation of national standards bodies that develops international standards.
A Technical Committee (ISO/TC211) is developing international Geographic Information/Geomatics standards. Among many other computing standards, ISO maintains an SQL standard and is developing an extended version, SQL3, which will support queries on geographic data sets.
Latitude
The angular distance of a point on the earth's surface along a meridian north or south of the equator. The Tropic of Cancer and the Tropic of Capricorn are parallels of latitude approximately 23 1/2 degrees north and south of the equator respectively.
Layer
A subset of a spatial data set that deals with one thematic topic.
LCDB
Land Cover Database. The Land Cover Database was created by the Remote Sensing Team in conjunction with the Department Of Conservation.
Line
A set of ordered co-ordinates that represent the shape of geographic features too narrow to be displayed as an area at the given scale (contours, street centrelines, or streams), or linear features with no area (county boundary lines). A lines is synonymous with an arc.
Linear Feature
A geographic feature that can be represented by a line or set of lines. For example, rivers, roads and electric and telecommunication networks can all be represented as linear features.
LINZ
Land Information New Zealand. LINZ and Terralink New Zealand Limited were both created in 1996 out of the old Department of Land and Survey Information. LINZ retained the public service functions of DOSLI and is a government department.
Longitude
The angular distance of a point on the earth's surface east or west of an arbitrarily defined meridian, usually the Greenwich meridian (Greenwich, England).
The Greenwich meridian was agreed in 1884 as being the central meridian from which all other meridians would be referenced to in order to calculate longitude.
Map Generalisation
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.
Map Join
An automated process for joining separate but adjacent map sheets into one. The result is a topologically consistent and physically continuous map.
Map Projection
A method of representing the earth's three-dimensional surface as a flat two-dimensional surface. This normally involves a mathematical model that transforms the locations of features on the earth's surface to locations on a two-dimensional surface. Because the earth is three-dimensional, some method must be used to depict the map in two dimensions. Therefore such representations distort some parameter of the earth's surface, be it distance, area, shape, or direction.
Also, the basic system of coordinates used to describe the spatial distribution of elements in a GIS.
Meridian
A line of longitude running vertically from the north pole to the south pole. Unlike lines of longitude, meridians terminate at the poles. The Prime Meridian, currently called the Greenwich Meridian (0), runs through Greenwich, England.
Metadata
Metadata is data about data. Used in the context of digital spatial data, metadata is the background information which describes the content, quality, condition, and other appropriate characteristics of the data.
Metadata may include: What it is about, where it is to be found, what is the quality of the data for a specified purpose, what spatial location does it cover and over what time period, when and where the data was collected and by whom, what purposes the data has been used for, and what related data sets are available.
Mosaicking
In spatial information systems: a synonym for map join. Usually refers to the joining of adjacent orthophotos. Mosaicking was one of the methods used in creating Terralink's Land Cover Database.
MSS
Multi-spectral Scanner System. A device, often carried in aeroplanes or satellites, for recording received radiation in several wavebands at the same time.
NRCD
National Road Centreline Database.
NZGD
New Zealand Geodetic Datum. The NZGD has changed from the NZGD 1949 to the NZGD 2000. It is the datum for survey data.
NZMG
New Zealand Map Grid.
Orthophotograph
An aerial photograph that has had all the distortions due to camera tilt and surface relief removed. An orthophoto has the advantages of a photograph (all visible features displayed) and the constant scale and accuracy of a map.
Parallel
Lines on the earth's surface that are parallel with the equator.
Parcel
A tract of land, being all or part of a legal estate.
Photogrammetry
The art and science of obtaining reliable quantitative and qualitative measurements through the use of photographs.
POA
Price on application
Polygon
A feature used to represent areas. A polygon is defined by the lines that make up its boundary and a point inside its boundary for identification. Polygons have attributes that describe the geographic feature they represent.
Primary Key
One or more attributes whose values uniquely identify a row in a database table.
Profile
A vertical sectional view of a surface derived by sampling surface values along a section line.
Raster
Raster images are made up of a regular grid of cells covering an area. Each cell must be rectangular in shape, although not necessarily square. Each cell within this matrix contains an attribute value as well as location co-ordinates. The spatial location of each cell is implicitly contained within the ordering of the matrix, unlike a vector structure which stores topology explicitly. Areas containing the same attribute value are recognised as such, however, raster structures cannot identify the boundaries of such areas as polygons. Also raster structures may lead to increased storage in certain situations, since they store each cell in the matrix regardless of whether it is a feature or simply 'empty' space. Televisions, computer monitors and digital orthophotos are raster images.
Record
In an attribute table, a single 'row' of thematic descriptors. In SQL terms, a record is analogous to a tuple.
A logical unit of data in a file. For example, there is one record in the ARC file for each arc in a coverage.
Rectification
A set of techniques for the elimination of errors in data. Rectification may be used to correct aerial photographs, remotely sensed data or analogue maps.
A computational process of converting an image or map from one co-ordinate system to another. Transformation, also known as rectification, typically involves rotation and scaling of grid cells, and thus requires resampling of values.
Registration
The process of geometrically aligning two or more cartographic data sets or digital images, in vertical juxtaposition, while maintain true geographic referencing.
Relational Database
A method of structuring data as collections of tables that are logically associated to each other by shared attributes so that relations between different entities and attributes can be used for data access and transformation. Any data element can be found in a relation by knowing the name of the table, the attribute (column) name, and the value of the primary key.
A database where information is arranged into tables and the dependencies between information is mapped by dependencies between two or more tables.
Relief Map
A map that appears to be or is in 3-dimensions.
Remote Sensing
The technique of obtaining data about the environment and the surface of the earth from a distance, for example, from aircraft or satellite.
Resolution
The smallest spacing between two display elements; the smallest size of feature that can be mapped or sampled.
Scanning
The process of taking analogue information and turning it into digital information. This is usually done from a hard copy map or aerial photograph to a raster image.
SIF
Standard interchange format, a spatial data exchange format. A standard or neutral format used to move graphics files between computer systems.
Spatial Database
A database containing information indexed by location.
Stereo Compilation
The process of capturing height data from aerial photographs.
Specifically, it refers to the analogue process.
Stereo Data Capture
The process of stereoscopically capturing data from aerial photographs. Data can also be captured by digitising single orthophotos.
Stereo(scopic) Plotter
A device for making topographical maps using stereo pairs of aerial photographs.
Thematic Map
A map showing information relating to specific themes, such as soil, land-use, population density, suitability for arable crops, etc.
Thematic information may be represented as labelled polygons. lines or points, chloropleth maps, isolines, etc.
Theme
A set of a class of objects specified, if applicable, by a name and feature class or dataset name, attributes of interest, or data classification scheme.
TIL
Terralink International Limited
Tile
Element of a tessellation database. Tiles subdivide the area covered by a map and organise the data by location (e.g., counties might be the tiles in a nation-wide database). A tile can be a regular, geometric shape (e.g., a map sheet), or an irregular shape, such as a county boundary.
A unit of organisation in a map library.
TLM
Topographic Line Map
Topographic Map
A map that shows terrain relief.
Topography
The configuration of a planetary surface including its relief and the position of its natural and man made features. The study of topography.
Topology
Topology
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 relative location of geographic phenomena independent of their exact position. In digital data, topological relationships such as connectivity, adjacency and relative position are usually expressed as relationships between nodes, links and polygons. For example, the topology of a line includes its from- and to-nodes, and its left and right polygons.
Transverse Mercator Projection
One of the most common projections on use - also known as Gauss Conform Projection. Suitable for mapping small areas, i.e. large scale mapping. It is a cylindrical projection contacting the Earth along any chosen Meridian. The Central meridian is true, other meridians and parallels are curved. It is a derivative of the Mercator Projection, which is a normal cylindrical projection, contacting the Earth along the Equator. The Mercator projection has lines of latitude and longitude projected as straight lines intersecting at 90 degrees. It is generally used for navigational charts but results in gross distortion in the vicinity of the Poles (consequently, the very top and bottom of the globe cannot be shown).
UTM
Universal Transverse Mercator.
Transverse Mercator Projection
Validation
Confirmation through the provision of objective evidence that the requirements for a specific or intended use or application have been fulfilled.
Vector
A quantity that is described by its magnitude and direction. The notation used to represent spatial information. Vector data structures are made up of points and lines that are organised into chains, arcs and polygons.
A coordinate-based data structure commonly used to represent linear geographic features. Each linear feature is represented as an ordered list of vertices. Traditional vector data structures include double-digitised polygons and arc-node models.
Vectorisation
The conversion of spatial data from any other data structure (usually raster) to a vector data structure. |
