ashtech GG Surveyor, Reference Manual

Page: 153 / 256

Command/Response Formats 135
Com
m
and
s
Table 6.45 outlines the GGA structure.
If there is no valid position, GGA still provides: time, position flag, number of
satellites, HDOP, age of corrections, and base station ID
If there are not enough satellites to compute HDOP, then the HDOP field is null. If
the receiver is not in Differential or RTK mode, then the age of corrections, base
station ID fields are null.
When running in the 5 Hz option, the GG Surveyor limits the number of available used satellites to
16.
Table 6.45: GGA Structure
Field Description Range
m1 Current UTC time of position fix in hours, minutes and seconds
(hhmmss.ss). 00 to 235959.50
m2 Latitude component of position in degrees, minutes and fraction
of minutes (ddmm.mmmmmm). 0 to 90°
c1 Latitude sector, N = North, S = South. ‘N’ or ‘S’
m3 Longitude component of position in degrees, minutes and
fraction of minutes (dddmm.mmmmmm). 0 to 180°
c2 Longitude sector, E = East, W = West. ‘E’ or ‘W’
d1 Position Type, n
1 = Autonomous position
2 = position differentially corrected
3 = RTK float
4 = RTK fixed 1, 2, 3, 4
d2 number of GPS satellites used in position computation. 3 to 24
f1 HDOP - horizontal dilution of precision 0 to 99.9
f2 Altitude in meters above the geoid. For 2-D position
computation this item contains the altitude held fixed. 0 to 30000.000
M Altitude units, M = meters. ‘M’
f3 Geoidal separation (value output only if Geoidal Height option
(G) is installed in the receiver). ±999.999
M Geoidal separation units, M = meters. ‘M’
f4 Age of the differential corrections, sss, in seconds. ±999.999
d3 Base station ID (RTCM only) 0 to 1023
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