Navman 11 User 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

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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