GUIDANCE MARINE RadaScan View, Installer'S Manual

Page: 60 / 69

DP Message Types (Continued)
MT Custom DP String
The MT Custom DP String adopts NMEA0183 conventions with a minimum length of 63 and maximum length of 80 characters.
It provides the same type of information for both CyScan and RadaScan sensors, including range and bearing to all tracked responders (similar to the MDL Multi-Target format). It also provides quality
information.
$PGNMT,T,HH˽MM˽SS.SSS,[NNNN]N,E,[IIII]I,S,[RRR]R.RR,Z
R
.Z
R
Z
R
,[BB]B.BB,Z
B
.Z
B
Z
B
,[Q]Q,[AAA]A,XXXX*CC<CR><LF>
Where:
•
$PGNMT
Proprietary header 6 chars
•
T
Type field indicating RadaScan system [R] 1 char
•
HH˽MM˽SS.SSS
Real-time clock time at message transmission to DP 12 chars
•
[NNNN]N
16-bit revolution counter in decimal 1–5 chars
•
E
Sequence identifier 1 char
•
[IIII]I
RadaScan 16-bit responder ID 1–5 chars
•
S
Status [V]oid, [A]vailable or [N]avigating 1 char
•
[RRR]R.RR
Range in metres 4–7 chars
•
Z
R
. Z
R
Z
R
Range standard deviation in metres 4 chars
•
[BB]B.BB
Bearing in degrees (clockwise from bow) 4–6 chars
•
Z
B
. Z
B
Z
B
Bearing standard deviation in degrees 4 chars
•
[Q]Q
Merit value 1–2 chars
•
[AAA]A
†
Age of measurement in ms 1–4 chars
•
XXXX
Reserved – 16-bit flags in hex 4 chars
•
*
Delimiter 1 char
•
CC
Checksum 2 chars
•
<CR><LF>
Carriage return and line feed 2 chars
†
The ‘age’ is the accumulated time in milliseconds from the moment the
measurement was made until the moment the message string is constructed,
prior to being transmitted to the DP system. It effectively gauges the lag through
the system, which may not be constant. Having a value for the lag allows for
subsequent correction of the measurement.
60