Raymarine AIS950 Installation Instructions Manual page 60

Technical reference
6.8.6 DTM - Datum reference
Logical geodetic datum and datum offsets from a reference datum.
$--DTM,ccc,a,x.x,a,x.x,a, x.x,ccc*hh<CR><LF>
Field
number
1 ccc =
2 a =
3 x.x, a =
5 x.x,a =
7 x.x =
8 ccc =
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 GBS - GNSS satellite fault detection
This sentence is used to support GNSS receiver autonomous integrity monitoring (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 information. To 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.
$--GBS, hhmmss.ss, x.x, x.x, x.x, xx, x.x, x.x, x.x *hh <CR><LF>
Field
number
1 hhmmss.ss
2 x.x
3 x.x
4 x.x
5 xx
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Description
Local datum
Local datum subdivision code - NOT USED
Lat offset, min, N/S - NOT USED
Longitude offset, min, E/W - NOT USED
Altitude offset, (meter) - NOT USED
Reference datum
Description
UTC time of the GGA or GNS fix associated with this sentence
Expected error in latitude
Expected error in longitude
Expected error in altitude - NOT USED
ID number of most likely failed satellite - NOT USED