# GIS Dictionary | Letter C

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Relating to land boundaries and subdivisions, parcels of land suitable for transfer of title. The legally recognized registration of the quantity, value and ownership of land parcels.

Cardinal Points
The four directions of north, south, east, and west.

Cartesian Coordinate System
In this system features on the earth’s surface are referenced to map locations using an XY coordinate system.

Cartogram
A type of map that uses a qualitative attribute to over or under-inflate the geographic depiction of an area.  See: Area Cartograms Explored.

Change Detection
A GIS technique for comparing the changes in a specific geographic area between two time periods.  See: Change Detection in GIS.

Clinometer
An instrument for measuring slopes or grades, heights, and distance.

Clip Analysis
Clip analysis is the function of using the extent of one geographic layer to clip the extent of another geographic layer. See: Clip Analysis using ArcGIS Desktop

Compass
A magnetic needle, mounted in a case or box, pivoted at its center, that always points to a general locality known as the magnetic north pole.

Conformal Projection
Projection which preserves the original shape of the area of interest but not the area or distance

Contour Line
An irregular curved line on a map joining all points of any given elevation, or a line all points of which are at the same elevation. See: Overview of Elevation Data.

Convergence of Information
The principle of using multiple indicators to deduce information.

Coordinate Geometry – COGO
A method of defining geometric features through the input of bearing and distance measurements. Coordinate Geometry (COGO) functions are typically used by land surveyors to enter traverses around spatial features such as parcels, to calculate precise locations and boundaries sing distances and bearings from reference points, and to define curves using a point location, radius, arc-length, and so on.

Coordinate System
The system used to measure horizontal and vertical distances on a planimetric map. A common coordinate system is used to spatially register geographic data for the same area.

Coordinates
X,Y input to denote a location on earth.

Coverage
A spatial dataset containing a common feature type. Coverages are also referred to as layers or themes.  Within ESRI’s ArcInfo 7.x GIS software, coverages are a specific type of geographic file type.