Installation Manual

34 Issue 1 AIS Installation Manual

transmits it over the VDL (if possible). It then sends an ABK sentence back to the requesting

device to indicate whether the transmission of the message s ucceeded or failed.

7.4.9 DTM – Datum reference

Local geodetic datum and datum offsets from a reference datum.

$--DTM,ccc,a,x.x,a,x.x,a,x.x,ccc*hh<CR><LF>

Reference datum

Altitude offset, m

Lon offset, min, E/W

Lat offset, min, N/S

Local datum subdivision code

Local datum

Note that the only datum supported by AIS is WGS84. The DTM sentence must be sent to the

transponder at a frequency of more than once every 30 seconds otherwise any positional

information sentences (eg GLL, GNS. RMC and GGA) will be ignored.

7.4.10 GBS – GNS satellite fault detection

This message is used to support receiver autonomous integrity monitoring (RAIM).

$--GBS,hhmmss.ss,x.x,x.x,x.x,xx,x.x,x.x,x.x,*hh<CR><LF>

Standard deviation of bias estimate

Estimate of bias on most likely failed satellite

Probability of missed detection for most likely failed satellite

ID number of most likely failed satellite

Expected error in altitude

Expected error in longitude

Expected error in attitude

UTC time of GGA or GNS fix associated with this sentence

7.4.11 GGA – Global positioning system (GPS) fix data

Time, position and fix-related data for a GPS receiver.

$--GGA,hhmmss.ss,IIII.II,a,yyyyy.yy,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh<CR><LF>

Differential reference

station ID

Age of differential GPS

data

Units of geoidal separation,

Geoidal separation

Units of antenna altitude, m

Antenna altitude

above/below mean sea

level (geoid)

Horizontal dilution of

precision

Number of satellites in use

GPS quality indicator

Longitude E/W

Latitude N/S

UTC of position