ashtech DG14, Reference Manual

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346 DG14 and DG16 Board & Sensor Reference Manual
Flattening
f = (a- b)/a = 1 - (1 - e
2
)
1/2
where
a = semimajor axis
b = semiminor axis
e = Eccentricity
GDOP
Geometric Dilution of Precision. The
relationship between errors in user
position and time and in satellite range.
GDOP
2
= PDOP
2
+ TDOP
2
. See
Position Dilution of Precision.
.
Geodetic datum (horizontal datum)
A specifically oriented ellipsoid typically
defined by eight parameters which
establish its dimensions, define its
center with respect to Earth's center of
mass and specify its orientation in
relation to the Earth's average spin axis
and Greenwich reference meridian.
Geodetic height (ellipsoidal height)
The height of a point above an
ellipsoidal surface. The difference
between a point's geodetic height and
its orthometric height equals the
geoidal height.
Geoid
The equipotential surface of the Earth's
gravity field which best fits mean sea
level. Geoids currently in use are
GEOID84 and GEOID90.
Geoidal height (geoidal separation;
undulation)
The height of a point on the geoid
above the ellipsoid measured along a
perpendicular to the ellipsoid.
GLL
Position Latitude/Longitude
GMST
Greenwich Mean Sidereal Time
GPS DIFF
Differential
GPS ICD-200
The GPS Interface Control Document is
a government document that contains
the full technical description of the
interface between the satellites and the
user. GPS receiver must comply with this
specification if it is to receive and
process GPS signals properly.
GPS week
GPS time started at Saturday/Sunday
midnight, January 6, 1980. The GPS
week is the number of whole weeks
since GPS time zero.
Greenwich mean time (GMT)
See universal time. In this text, they are
often used interchangeably.
HDOP
Horizontal Dilution of Precision. See
Dilution of Precision.
HI
Height of Instrument
HTDOP
Horizontal/Time Dilution of Precision.
See Dilution of Precision.
ID
Identification or Integrated Doppler
Integer bias terms
The receiver counts the carrier waves
from the satellite, as they pass the