Maps GPS Glossary - C
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.