Navman 12 Designer's Manual page 73

GPS accuracy that uses pseudo-range errors
recorded at a known location to improve the
measurements made by other GPS receivers
within the same general geographic area.
DI: Double Precision Integer.
Doppler aiding: a signal processing strategy,
which uses a measured doppler shift to help a
receiver smoothly track the GPS signal to allow a
more precise velocity and position measurement.
DoD: Department of Defense.
DOP: Dilution of Precision (see GDOP, HDOP,
PDOP, TDOP, and VDOP).
DOS: Disk Operating System.
DSP: Digital Signal Processor.
DTR: Data Terminal Ready.
ECEF: Earth-Centred Earth-Fixed. A Cartesian
coordinate system with its origin located at the
centre of the Earth. The coordinate system used by
GPS to describe three-dimensional location. For
the WGS-84 reference ellipsoid, ECEF coordinates
have the Z-axis aligned with the Earth's spin axis,
the X-axis through the intersection of the prime
meridian and the equator and the Y-axis is rotated
90 degrees east of the X-axis about the Z-axis.
EEPROM: Electrically Erasable Programmable
Read-Only Memory.
EFP: Extended Floating Point.
EHPE: Expected Horizontal Position Error.
EMC: Electromagnetic Compatibility
EMI: Electromagnetic Interference.
Ephemeris: a set of satellite orbital parameters
that is used by a GPS receiver to calculate
precise GPS satellite positions and velocities. The
ephemeris is used to determine the navigation
solution and is updated frequently to maintain the
accuracy of GPS receivers.
EPROM: Erasable Programmable Read Only
Memory.
ESD: Electrostatic Discharge.
EVPE: Expected Vertical Position Error.
FOM: Figure Of Merit.
FP: Floating Point.
FRP: Federal Radio-navigation Plan. The U.S.
Government document which contains the official
policy on the commercial use of GPS.
GaAs: Gallium Arsenide.
GDOP: Geometric Dilution of Precision. A
factor used to describe the effect of the satellite
geometry on the position and time accuracy of the
MN002000A © 2004 Navman NZ Ltd. All rights reserved. Proprietary information and specifications subject to change without notice.
GPS receiver solution. The lower the value of the
GDOP parameter, the less the error in the position
solution. Related indicators include PDOP, HDOP,
TDOP, and VDOP.
GMT: Greenwich Mean Time.
GPS: Global Positioning System. A space-based
radio positioning system which provides suitably
equipped users with accurate position, velocity,
and time data. When fully operational, GPS
will provide this data free of direct user charge
worldwide, continuously, and under all weather
conditions. The GPS constellation will consist of 24
orbiting satellites, four equally spaced around each
of six different orbital planes.
GPSRE: GPS Receiver Engine.
GPS Time: the number of seconds since
Saturday/Sunday midnight UTC, with time zero
being this midnight. Used with GPS week to
determine a specific point in GPS time.
GPS Week: the number of weeks since January
6, 1980, with week zero being the week of January
6,1980. Used with GPS Time to determine a
specific point in GPS time.
HDOP: Horizontal Dilution of Precision. A measure
of how much the geometry of the satellites affects
the position estimate (computed from the satellite
range measurements) in the horizontal (East,
North) plane.
Held altitude: the altitude value that will be sent
to the Kalman filter as a measurement when in
Altitude Hold Mode. It is an Auto Hold Altitude
unless an Amended Altitude is supplied by the
application processor.
HDOP: Horizontal Dilution of Precision
Hz: Hertz.
IF: Intermediate Frequency.
IGRF: International Geomagnetic Reference Field.
I/O: Input/output.
lODE: Issue Of Data Ephemeris.
JPO: Joint Program Office. An office within
the U.S. Air Force Systems Command, Space
Systems Division. The JPO is responsible for
managing the development and production
aspects of the GPS system and is staffed by
representatives from each branch of the U.S.
Military, the U.S. Department of Transportation,
Defense Mapping Agency, NATO member nations,
and Australia.
Kalman Filter: Sequential estimation filter which
combines measurements of satellite range and
range rate to determine the position, velocity, and
time at the GPS receiver antenna.
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