Using the External Computer Data Link
MicronNav System
0656-SOM-00001-07
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© Tritech International Ltd.
7.2.6. NMEA $RATTM
This NMEA ‘Tracked Target Message’ is a commonly used string in charting/navigation
packages. The comma-separated ASCII string contains the target Range & Bearing and UTC
Time-stamp. Target speed and course are not calculated and so are not contained in the
string. Any fields with no calculated data will be padded with zero value data.
The full string format is as follows:
‘$RATTM’ Reply Data Structure
Data Description
Data Range
Field Range
NMEA string header
Always ‘$RATTM’
hhhhhh
Comma separator
Always ‘,’
,
Target number
00 to 99
ii
Comma separator
Always ‘,’
,
Horizontal Target Distance from vessel (in
nautical miles)
0 to 9.9999
d.dddd
Comma separator
Always ‘,’
,
Target Bearing (degrees)
0 to 359.9
bbb.b
Comma separator
Always ‘,’
,
Bearing Degrees identifier
‘R’ or ‘T’
‘R’ (Relative) or ‘T’ (True)
Comma separator
Always ‘,’
,
Target Speed, not calculated so padded
with zero
Always ‘0.0’
s.s
Comma separator
Always ‘,’
,
Target Course, not calculated so padded
with zero
Always ‘0.0’
c.c
Comma separator
Always ‘,’
,
Degrees identifier, unused so defaulted to
‘T’
‘R’ or ‘T’
‘R’ (Relative) or ‘T’ (True)
Comma separator
Always ‘,’
,
Distance of closest point of approach, not
calculated so padded with zero
Always ‘0.0’
p.p
Comma separator
Always ‘,’
,
Time to CPA, min, ("-" increasing), not
calculated so padded with zero
Always ‘0.0’
t.t
Comma separator
Always ‘,’
,
Speed/Distance units
Always ‘N’ (nautical miles) K/N/S (km/ nautical miles/
statue miles)
Comma separator
Always ‘,’
,
Target name (0 = Responder, 1..15 =
Transponder)
e.g. “TARGET0” to
“TARGET1”
ASCII variable field
Comma separator
Always ‘,’
,
Target Status
‘L’ or ‘T’
L = Lost, Q = Query in
process, T = Tracking
Comma separator
Always ‘,’
,
Target ?
Always null
R = Reference Target,
otherwise null
