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 Earthï¿½s 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 ï¿½upï¿½.
crosstrack error – The lateral distance in either dirction you are off the desired course.
cutoff angle – The receiverï¿½s 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.