gazetteer
A list of geographical place or feature names in alphabetical order, usually accompanied by geographic or grid coordinates and basic information about the feature, such as population or classification.
generalization
(1) The simplification of shape by the omission of non-essential information, (2) the combining of small shapes and (3) the enlargement of certain features essential to the map.
geodesy
The science which describes the size and shape of the Earth in mathematical terms by such direct measurements as triangulation, leveling and gravimetric observations. The aim of geodesy is to support the establishment of a coordinate system used to locate points on the Earth's surface.
geographic centre
The point at which a geographical region could be balanced if it were an area of uniform thickness and density. The geographic centre of Canada is near the community of Arviat in the Northwest Territories, at latitude 61° 06' 30" N, longitude 94° 03' 30" W.
geography
The science which involves a combination of physical and cultural disciplines which are used to describe, explain and help us to understand our environment and our relationship to it.
geoid
The figure of the Earth considered as a mean sea-level surface extended continuously under the continents.
geomatics
Refers to the disciplines that acquire, store, manage, retrieve, manipulate and distribute spatial or geographically referenced data.
Geomatics Canada
Formerly called The Surveys, Mapping and Remote Sensing Sector, this agency of the Canadian Federal Government (part of the Earth Sciences Sector, Natural Resources Canada) is responsible for delivering the federal government's geomatics activities and fostering growth in the Canadian geomatics industry.
georeference
The process of establishing a relationship between data in Cartesian coordinates on a flat map to known ground-truth geographic coordinates. (See Cartesian coordinate system).
GIS, Geographic Information System
A computer-based information system designed to handle georeferenced data which has, also the capability to efficiently capture, store, update, manipulate, analyze, display and output a full range of geographical data. Output can be in many forms: either as tables, graphics, or maps.
globe
A scaled down spherical representation or model of the Earth. A map on a sphere.
glossary
An alphabetical list of technical terms and their explanations. A dictionary of technical terms.
gnomonic map projection
A planar map projection which is tangent to the globe at a single point, but may be oriented at any aspect. The projection views the Earth's surface from the centre of the globe. In the polar case, parallels are represented by a system of concentric circles sharing a common point of origin from which radiate the meridians, spaced at true angles. This map projection is primarily used for navigational purposes, as all great circles are represented as straight lines. It may be the oldest map projection, possibly being used by Thales for charts of the heavens, circa 640-548 B.C.
gore
A cresent-shaped map of a region of the Earth between two lines of longitude, which may be fitted to the surface of a globe with a minimum of distortion.
GPS, Global Positioning System
A surveying method that uses a set of 24 satellites in geostationary position high above the Earth. Specially designed GPS receivers, when positioned at a point on Earth, can measure the distance from that point to three or more orbiting satellites. The coordinates of the point are determined through the geometric calculations of triangulation. GPS provides accurate geodetic data for any point on the Earth.
gradient
An expression of slope or an angle of slope. Gradient may be expressed as a fraction or percentage, for example, 1/50 (1 in 50) metres indicates that the elevation changes (rises or falls) by one metre in a horizontal distance of 50 metres (or a 2% grade).
GUI, graphical user interface
A method of interacting with a computer system by using a mouse to point-and-click on graphic symbols (icons, glyphs or menus) which are displayed on the computer monitor. The GUI method allows the user to access software applications and tools with a minimum of keyboarding.
graticule
A network of longitude and latitude lines on a map or chart, providing the basis for a geographical coordinate system with the capability of relating points on a map to their true locations on the Earth.
gravure
A method of printing in which the image is etched into the surface of the printing plate and is therefore, recessed below the surface of the plate. Ink is captured in the recesses of the image and is transferred to paper under firm pressure. (Also called photogravure).
great circle
A circle on the surface of a sphere produced by any plane which passes through the centre of the sphere and intersects the sphere's surface. (Also called an orthodrome).
great circle route
The shortest distance between any two points on a nearly spherical surface like the Earth, is along the arc of a great circle connecting the two points.
Greenwich Meridian
The meridian, or line of longitude adopted by international agreement (in 1884) to be the 0° meridian from which all longitudes worldwide would be calculated. (Also called the prime or international meridian).
grid
A network of regularly spaced straight lines intersecting at right angles and used as a basis for rectangular coordinate map reference systems.
grid reference system
A locational reference system consisting of a grid and a method of referring to points on the grid so that locations can be provided coordinates.
ground truth data
The coordinates of a location calculated by accurate measurement on the Earth's surface, as opposed to locational coordinates determined by some other less accurate method, for example, based on a representation of the Earth such as a map.