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-8.9-
RMC - Recommended specific GPS/TRANSIT data
Time, date, position, course and speed data provided by a GPS or TRANSIT navigation receiver.
Checksum is mandatory in this sentence. This sentence is transmitted at intervals not exceeding 2
s and is always accompanied by RMB when a destination waypoint is active. RMC and RMB are
the recommended minimum data to be provided by a GPS or TRANSIT receiver. All data fields
must be provided, null fields used only when data is temporarily unavailable.
NOTE 1: Easterly variation (E) subtracts from true course. Westerly variation (W) adds to true course.
NOTE 2: Positioning system Mode indicator:
A= Autonomous mode
D= Differential mode
E= Estimated (dead reckoning) mode
M= Manual input mode
S= Simulator mode
N= Data not valid
NOTE 3: The positioning system Mode indicator field supplements the Status field (field No.2), which shall be
set to V = invalid for all values of Mode indicator except for A = Autonomous and D = Differential. The
positioning system Mode indicator and Status fields shall not be null fields.
$--RMC, hhmmss.ss, A, llll.ll, a yyyyy.yy, a, x.x, x.x, xxxxxx, x.x,a, a*hh<CR><LF>
Checksu, mandatory for RMC
Mode indicator (see notes 2 and 3)
Magnetic variation, degrees, E/W (see note 1)
Course over ground, degrees true
Longitude, E/W
Data: dd/mm/yy*
Latitude, N/S
UTC of position fix*
*: Not used
Speed over ground, knots
Status (see note 3) A= data valid V= navigation receiver warning
RSD - Radar system data
IMO Resolution A.477 (XII). Radar display setting data.
$--RSD, x.x, x.x, x.x, x.x, x.x, x.x, x.x, x.x, x.x, x.x, x.x, a, a*hh<CR><LF>
Checksum
Display rotation (see note 1)
Range units, K/N/S
Range scale in use
Cursor bearing, degrees clockwise from 0°
Cursor range, from own ship
EBL 2, degrees
VRM 2, range
Origin 2 bearing (see note 2) *
Origin 2 range (see note 2) *
Bearing line 1 (EBL 1), degrees from 0°
Variable range marker 1 (VRM 1), range
Origin 1 bearing, degrees from 0° (see note 2) *
Origin 1 range, from own ship (see note 2) *
* Not used
NOTES 1 Display rotation: C = course-up, course-over-ground up, degrees true
H = head-up, ship’s heading (center-line) 0° up
N = north-up, true north is 0° up
2 Origin 1 and 2 are located at the stated range and bearing from own ship and provide for two independent
sets of variable range markers (VRM) and electronic bearing lines (EBL) originating away from own ship
position.