User's Manual

Technical reference
Page 60
6.8.6 DTM - Datum reference
Logical geodetic datum and datum offsets from a reference
datum.
Possible datum and reference datum values are:
● WGS84 = W84
● WGS72 = W72
● SGS85 = S85
● PE90 = P90
● User
defined =999 (only available for “Local datum”)
● IHO datum code ( „ -„- „ -„- -„- )
6.
8.7 G
BS - GNSS satellite fault detection
This sentence is used to support GNSS receiver autonomous integrity m
onitoring (RAIM). Given that a GNSS
receiver is tracking enough satellites to perform integrity checks of the positioning quality of the position
solution, a message is needed to report the output of this process to other systems to advise the system user.
With the RAIM in the GNSS receiver, the receiver can isolate faults to individual satellites and not use them in
its position and velocity calculations. Also, the GNSS receiver can still track the satellite and easily judge when
it is back within tolerance.
This sentence shall be used for reporting this RAIM infor
m
ation
.
T
o perform this integrity function, the GPS
receiver must have at least two observables in addition to the minimum required for navigation. Normally these
observables take the form of additional redundant satellites.
$--DTM,ccc,a,x.x,a,x.x,a, x.x,ccc*hh<CR><LF>
Field
number
Description
1 ccc = Local datum
2 a = Local datum subdivision code - NOT USED
3 x.x, a = Lat offset, min, N/S - NOT USED
5 x.x,a = Longitude offset, min, E/W - NOT USED
7 x.x = Altitude offset, (meter) - NOT USED
8 ccc = Reference datum
$--GBS, hhmmss.ss, x.x, x.x, x.x, xx, x.x, x.x, x.x *hh <CR><LF>
Field
number
Description
1 hhmmss.ss UTC time of the GGA or GNS fix associated with this sentence
2 x.x Expected error in latitude
3 x.x Expected error in longitude
4 x.x Expected error in altitude - NOT USED
5 xx ID number of most likely failed satellite - NOT USED