C/A code – Coarse Acquisition code – The GPS signal for civilian use (also used by the military to get an initial fix).

cadastral map – The type of map that is used to show the ownership and the boundaries of land parcels.

cadastre – A public record, survey or map of a real property that includes details of ownership, tenure, locations, dimensions and value. This stands as a basis for taxations.

calibration – The process of associating map information held in an image file with its location on the earth so that, for example, each pixel becomes associated with a latitude and longitude allowing routes and tracks to be correctly plotted and displayed.

carolina bay – An elliptical depression that is rich in biodiversity and that can be found in the plains of mideastern and southeastern United States.

carrier-aided tracking – A method to improve accuracy by using the GPS carrier signal to get a more precise lock on the pseudorandom code.

carrier frequency – The frequency generated by an unmodulated electrical wave sent by a radio, radar or any other transmitting device.

carrier phase – The GPS measurements made on the L1 or L2 carrier signal of a satellite.

cartographer – A person who makes maps.

cartography – The art or technique of making maps or charts.

CDI – See course deviation indicator.

CDMA – See code division multiple access.

census – The count of population that lives in one area.

CEP – Circular Error Probable – The radius of a circle within which fifty percent of positioning solutions fall. CEP is used to achieve horizontal accuracy.

CF – Compact Flash – A standard that PDAs, laptops, and other computer-related devices use to accept removable accessories such as additional memory or GPS receivers.

channel – Circuitry necessary to receive the signal from one GPS satellite.

chart – A type of map that is primarily made for nautical and aeronautical navigation.

chartplotter – A device that overlays GPS data on to marine navigational charts.

choropleth map – The type of map in which certain areas are shaded or patterned in proportion to the measurement of the statistical variable that is shown on the map.

Circle of Antarctic – Circle of latitude that marks the southern extremity of the polar day (24-hour sunlit day) and the polar night (24-hour sunless night). This happens at least once a year.

Circle of Arctic – Circle of latitude that marks the northern extremity of the polar day (24-hour sunlit day) and the polar night (24-hour sunless night). This happens at least once a year.

circular error probable – See CEP.

cirque – Amphitheatre-like valley head occurring at the head of a mountain valley.

Clarke 1866 – The reference spheroid for the NAD27 coordinate system.

clinometer – A device, usually similar to a compass, used to measure vertical angles, as in the slope of a hill.

clinometric map – The type of map where slopes are represented with colors or shading.

clock bias – The difference between GPS receiver clock value and another time reference.

clock offset – A constant difference in the time reading between two clocks, normally used to indicate a difference between two time zones.

CMG – see course made good

code division multiple access – A technique whereby multiple radios use the same frequency. One of its uses is for unique cross-correlation.

code phase – The GPS measurements made on the C/A-Code.

COG – see course over ground

cold start – The ability of a GPS receiver to start giving position data without any almanac data stored in its memory.

collar – The area surrounding the actual map itself containing necessary information such as scale, legend, latitude and longitude, etc.

compact flash – See CF.

continent – The largest landmass on Earth.

constellation – 1) All GPS satellites. 2) The satellites visible to a GPS receiver at one time.

continental margin – The zone of transition from a continent to the adjacent ocean basin. It usually includes a continental shelf, continental slope, and continental rise.

continental rise – The gently sloping surface located at the base of a continental slope.

continental shelf – The submerged margin of a continental mass extending from the shore to the first prominent break in slope.

continental slope – The slope that extends from a continental shelf down to the ocean basin. In some areas, such as off eastern North America, the continental slope grades into the more gently sloping continental rise.

contour interval – The difference, in feet or meters, in elevation between two adjacent contour lines.

contour line – A line on a topographic map that represents a specific elevation.

control point – Also called a control station. Locations on the earth’s surface used for mapping references. Can be horizontal or vertical or both. Often these are bench marks.

control segment – Satellite operators that command and monitor the GPS satellite constellation.

CONUS – Contiguous (or Continental) United States.

coordinated universal time – The time standard used to regulate time in the entire world. It is based on an atomic clock that adds leap seconds in order to compensate for the Earth�s slowing rotation.

coordinates – A set of numbers that represents a precise location anywhere on Earth. Usually stated as latitude and longitude.

coulee – Valley or deep ravine that is often dry in summer.

course – The direction from the starting waypoint or location to the destination waypoint, measured in degrees.

course deviation indicator – Instrument used to determine the magnitude and direction of crosstrack error.

course made good – The bearing from the “active from” waypoint to the current position, independent of the path taken to arrive at the current position.

course over ground – The direction of movement relative to the Earth.

course to steer – The heading you need to maintain in order to reach a destination.

course up orientation – The adjustment made by a GPS device to the map display in order that the direction of navigation will always be �up�.

crosstrack error – The lateral distance in either dirction you are off the desired course.

cutoff angle – The receiver�s minimum acceptable satellite elevation angle in order to avoid too high Tropospheric or Ionospheric Delay values or blockage of line-of-sight.

CWM – See cirque.