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Lassen-SK8 Embedded GPS Module Glossary-3
Glossary
DGPS reference station A device that tracks all GPS satellites in view, periodically performs
inter-channel calibrations, and calculates and transmits differential
corrections.
differential capable A term used to describe a GPS receiver that is capable of receiving and
applying differential GPS corrections.
differential GPS A procedure of correcting GPS solutions to achieve improved position
accuracy. Differential GPS provides 2 to 5 meter position accuracy.
Differential accuracy is obtained by applying corrections determined by
the stationary Differential GPS Reference Station to the GPS data
collected by the RPU unit on-board the vehicle.
differential processing GPS measurements can be differenced between receivers, satellites, and
epochs. Although many combinations are possible, the present
convention for differential processing of GPS phase measurements is to
take differences between receivers (single difference), then between
satellites (double difference), then between measurement epochs (triple
difference).
differential relative
positioning
Determination of relative coordinates of two or more receivers which are
simultaneously tracking the same satellites. Static differential GPS
involves determining baseline vectors between pairs of receivers. Also
see differential GPS
dilution of precision A description of the purely geometrical contribution to the uncertainty in
a position fix, given by the expression DOP = SQRT TRACE (A A)
where A A is the design matrix for the instantaneous position solution
(dependent on satellite-receiver geometry). The DOP factor depends on
the parameters of the position-fix solution. Standard terms for the GPS
application are:
GDOP: Geometric (three position coordinates plus clock offset in the
solution)
PDOP: Position (three coordinates)
HDOP: Horizontal (two horizontal coordinates)
VDOP: Vertical (height only)
TDOP: Time (clock offset only)
DOP see dilution of precision.
Doppler aiding The use of Doppler carrier-phase measurements to smooth code-phase
position measurements.
Doppler shift The apparent change in frequency of a received signal due to the rate of
change of the range between the transmitter and receiver.
earth-centered earth-fixed Cartesian coordinate system where the X direction is the intersection of
the prime meridian (Greenwich) with the equator. The vectors rotate with
the earth. Z is the direction of the spin axis.
elevation angle The angle between the line of sight vector and the horizontal plane.
2-D Two Dimensional. A 2-D position is defined as latitude and longitude.
Altitude is assumed to be fixed.