nmea.txt

我在项目开发过程中搜集的各种NMEA协议文档

This is a list of NMEA 0183 sentences with field descriptions.
It is primarily intended to help people understand GPS reports.

This list may originally have been redacted from the document cited as
[NMEA2000]; see the list of sources at the end of this document.
The official NMEA standard was not consulted at any point, thus this
document is not a derivative work of that standard and is not
controlled by the rapacious lawyers of NMEA.

It is originally from the gpsdrive distribution, but adds more
information on the following topics:

* Old and new forms of VTG
* Units used in GGA
* Vendor extensions PRWIZCH and PMGNST
* FAA Mode Indicator field for RMC, RMB, VTG, GLL, BWC, XTE.
* New documentation on BWC, DTM, GBS, GRS, GST, MSK, and MSS sentences.
* Sentence examples merged from [GIDS]
* Sentence explanations from [GIDS] and elsewhere
* Corrected badly mangled ZDA description.
* Corrected DPT titling
* Common talker IDs
* Sentences HFB, ITS, TPC, TDS, TFI, TPC, TPR, TPT from [GLOBALSAT].

Many of these are only emitted by high-end maritime navigation systems.
Most GPS sensors emit only RMC, GSA, GSV, GLL, and VTG.  Note that the
form of VTG is variable with NMEA version.

In NMEA 2.3, several sentences (APB, BWC, BWR, GLL, RMA, RMB, RMC,
VTG, WCV, and XTE) got a new last field carrying the signal integrity
information needed by the FAA.  (The values in the GGA mode field were
extended to carry this information as well.) Here are the values:

FAA Mode Indicator
     A = Autonomous mode
     D = Differential Mode
     E = Estimated (dead-reckoning) mode
     M = Manual Input Mode
     S = Simulated Mode
     N = Data Not Valid

This field may be empty.  In pre-2.3 versions it is omitted. [NTUM] says
that according to the NMEA specification, it dominates the Status field --
the Status field will be set to "A" (data valid) for Mode Indicators A
and D, and to "V" (data invalid) for all other values of the Mode
Indicator.  This is confirmed by [IEC].

Where a numeric latitude or longitude is given, the two digits
immediately to the left of the decimal point are whole minutes, to the
right are decimals of minutes, and the remaining digits to the left of
the whole minutes are whole degrees.

Eg. 4533.35 is 45 degrees and 33.35 minutes. ".35" of a minute is
exactly 21 seconds.

Eg. 16708.033 is 167 degrees and 8.033 minutes. ".033" of a minute is
about 2 seconds.

According to [UNMEA], the NMEA standard requires that a field (such as
altitude, latitude, or longitude) must be left empty when the GPS has
no valid data for it.  However, many receivers violate this.  It's
common, for example, to see latitude/longitude/altitude figures filled
with zeros when the GPS has no valid data.

The physical-level protocol is RS232C-compatible (actually RS422),
4800bps, 8N1 or 7N2 (the latter is rare but does occur; the FV18 from
San Jose Navigation uses it, for example).  The data is all
ASCII, the high bit is not used.

It appears there is an international standard, IEC 61162-1, published
in 2000, that is essentially NMEA 0183.  [IEC] says "is closely
aligned with NMEA 0183 version 2.30".  Unfortunately, it costs money
and is not redistributable.

Here are the NMEA-standard sentences.  The names are listed without the
"talker ID", a two-character prefix that identifies the type of the 
transmitting unit.  By far the most common talker ID is "GP",
identifying a generic GPS, but all of the following
are well known:

		GP      Global Positioning System receiver
		LC      Loran-C receiver
		II      Integrated Instrumentation
		IN	Integrated Navigation
		EC      Electronic Chart Display & Information System (ECDIS)
		CD	Digital Selective Calling (DSC)

LC - LORAN-C is a marine navigation system run by the U.S. government,
which is planning to shut it down in favor of GPS.  Some non-LORAN
devices emit GLL but use this talker ID for backward-compatibility
reasons, so it may outlast the actual LORAN system.

II - II is emitted by the NMEA interface of a widely-used line of
marine-navigation electronics called the AutoHelm Seatalk system, made
by Raytheon; see also [SEATALK]. 

IN -- Some Garmin GPS units use an IN talker ID.

EC -- ECDIS is a specialized geographical information system intended
to support professional maritime navigation.  NMEA talker units
meeting the ECDIS standard use this prefix.  Some of these emit GLL.

CD -- Modern marine VHF radios have a set of logic collectively known as
Digital Selective Calling (DSC).  These radios typically take data
from a local position indicating device.  This data is used in
conjunction with a unique (FCC assigned) ID to cause your radio to
broadcast your position data to others.  Conversely, these radios are
capable of recieving position data of other stations and emitting
sentences indicating other station positions.  This lets you plot the
position of other vessels on a chart, for instance.  There has been at
least one instance of a DSC enabled radio overloading (mis-using) the
LC talker prefix for this purpose.  Otherwise they use the CD prefix.
A vessel's nav system is likely to have both CD and some other
position indicating talker on its bus(es).

Until the U.S. Coast Guard terminated the Omega Navigation System in
1997, another common talker prefix was "OM" for an Omega Navigation
System receiver.

Here is a more complete list of talker ID prefixes.  Most are not
relevant to GPS systems.

AG	Autopilot - General
AP	Autopilot - Magnetic

CC	Computer - Programmed Calculator (outdated)
CD	Communications - Digital Selective Calling (DSC)
CM	Computer - Memory Data (outdated)
CS	Communications - Satellite
CT	Communications - Radio-Telephone (MF/HF)
CV	Communications - Radio-Telephone (VHF)
CX	Communications - Scanning Receiver

DE	DECCA Navigation (outdated)
DF	Direction Finder

EC	Electronic Chart Display & Information System (ECDIS)
EP	Emergency Position Indicating Beacon (EPIRB)
ER	Engine Room Monitoring Systems

GP	Global Positioning System (GPS)

HC	Heading - Magnetic Compass
HE	Heading - North Seeking Gyro
HN   	Heading - Non North Seeking Gyro

II	Integrated Instrumentation
IN	Integrated Navigation

LA	Loran A (outdated)
LC	Loran C

MP	Microwave Positioning System (outdated)

OM	OMEGA Navigation System (outdated)
OS	Distress Alarm System (outdated)

RA	RADAR and/or ARPA

SD	Sounder, Depth
SN	Electronic Positioning System, other/general
SS	Sounder, Scanning

TI	Turn Rate Indicator
TR      TRANSIT Navigation System

VD	Velocity Sensor, Doppler, other/general
DM	Velocity Sensor, Speed Log, Water, Magnetic
VW	Velocity Sensor, Speed Log, Water, Mechanical

WI	Weather Instruments 

YC	Transducer - Temperature (outdated)
YD	Transducer - Displacement, Angular or Linear (outdated)
YF	Transducer - Frequency (outdated)
YL	Transducer - Level (outdated)
YP	Transducer - Pressure (outdated)
YR	Transducer - Flow Rate (outdated)
YT	Transducer - Tachometer (outdated)
YV	Transducer - Volume (outdated)
YX      Transducer

ZA	Timekeeper - Atomic Clock
ZC	Timekeeper - Chronometer
ZQ	Timekeeper - Quartz
ZV	Timekeeper - Radio Update, WWV or WWVH

------------------------------------------------------------------------------

 AAM - Waypoint Arrival Alarm

This sentence is generated by some units to indicate the Status of
arrival (entering the arrival circle, or passing the perpendicular of
the course line) at the destination waypoint.

        1 2 3   4 5    6
        | | |   | |    |
 $--AAM,A,A,x.x,N,c--c*hh<CR><LF>

 Field Number: 
 1) Status, BOOLEAN, A = Arrival circle entered
 2) Status, BOOLEAN, A = perpendicular passed at waypoint
 3) Arrival circle radius
 4) Units of radius, nautical miles
 5) Waypoint ID
 6) Checksum

Example: GPAAM,A,A,0.10,N,WPTNME*43

WPTNME is the waypoint name.

------------------------------------------------------------------------------

 ALM - GPS Almanac Data

This sentence expresses orbital data for a specified GPS satellite.

        1   2   3  4   5  6    7  8    9    10     11     12     13     14  15   16
        |   |   |  |   |  |    |  |    |    |      |      |      |      |   |    |
 $--ALM,x.x,x.x,xx,x.x,hh,hhhh,hh,hhhh,hhhh,hhhhhh,hhhhhh,hhhhhh,hhhhhh,hhh,hhh,*hh<CR><LF>

 Field Number: 
  1) Total number of messages
  2) Message Number
  3) Satellite PRN number (01 to 32)
  4) GPS Week Number :
	Date and time in GPS is computed as number of weeks from 6 January 1980 plus
     	number of seconds into the week.
  5) SV health, bits 17-24 of each almanac page
  6) Eccentricity
  7) Almanac Reference Time
  8) Inclination Angle
  9) Rate of Right Ascension
 10) Root of semi-major axis
 11) Argument of perigee
 12) Longitude of ascension node
 13) Mean anomaly
 14) F0 Clock Parameter
 15) F1 Clock Parameter
 16) Checksum

Example: $GPALM,1,1,15,1159,00,441d,4e,16be,fd5e,a10c9f,4a2da4,686e81,58cbe1,0a4,001*5B

------------------------------------------------------------------------------

 APA - Autopilot Sentence "A"

This sentence is sent by some GPS receivers to allow them to be used
to control an autopilot unit. This sentence is commonly used by
autopilots and contains navigation receiver warning flag status,
cross-track-error, waypoint arrival status, initial bearing from
origin waypoint to the destination, continuous bearing from present
position to destination and recommended heading-to-steer to
destination waypoint for the active navigation leg of the journey.

        1 2  3   4 5 6 7  8  9 10    11
        | |  |   | | | |  |  | |     |
 $--APA,A,A,x.xx,L,N,A,A,xxx,M,c---c*hh<CR><LF>

 Field Number: 
  1) Status
     V = LORAN-C Blink or SNR warning
     V = general warning flag or other navigation systems when a reliable
         fix is not available
  2) Status
     V = Loran-C Cycle Lock warning flag
     A = OK or not used

  3) Cross Track Error Magnitude
  4) Direction to steer, L or R
  5) Cross Track Units (Nautic miles or kilometers)
  6) Status
     A = Arrival Circle Entered
  7) Status
     A = Perpendicular passed at waypoint
  8) Bearing origin to destination
  9) M = Magnetic, T = True
 10) Destination Waypoint ID
 11) checksum

Example: $GPAPA,A,A,0.10,R,N,V,V,011,M,DEST,011,M*82

------------------------------------------------------------------------------

 APB - Autopilot Sentence "B"

This is a fixed form of the APA sentence with some ambiguities removed.

Note: Some autopilots, Robertson in particular, misinterpret "bearing
from origin to destination" as "bearing from present position to
destination". This is likely due to the difference between the APB
sentence and the APA sentence. for the APA sentence this would be the
correct thing to do for the data in the same field. APA only differs
from APB in this one field and APA leaves off the last two fields
where this distinction is clearly spelled out. This will result in
poor performance if the boat is sufficiently off-course that the two
bearings are different.
                                         13    15
        1 2 3   4 5 6 7 8   9 10   11  12|   14|
        | | |   | | | | |   | |    |   | |   | |
 $--APB,A,A,x.x,a,N,A,A,x.x,a,c--c,x.x,a,x.x,a*hh<CR><LF>

 Field Number: 
  1) Status
     V = LORAN-C Blink or SNR warning
     V = general warning flag or other navigation systems when a reliable
         fix is not available
  2) Status
     V = Loran-C Cycle Lock warning flag
     A = OK or not used
  3) Cross Track Error Magnitude
  4) Direction to steer, L or R
  5) Cross Track Units, N = Nautical Miles
  6) Status
     A = Arrival Circle Entered
  7) Status
     A = Perpendicular passed at waypoint
  8) Bearing origin to destination
  9) M = Magnetic, T = True
 10) Destination Waypoint ID
 11) Bearing, present position to Destination
 12) M = Magnetic, T = True
 13) Heading to steer to destination waypoint
 14) M = Magnetic, T = True
 15) Checksum

Example: $GPAPB,A,A,0.10,R,N,V,V,011,M,DEST,011,M,011,M*82

------------------------------------------------------------------------------

 BOD - Bearing - Waypoint to Waypoint

        1   2 3   4 5    6    7
        |   | |   | |    |    |
 $--BOD,x.x,T,x.x,M,c--c,c--c*hh<CR><LF>

 Field Number: 
  1) Bearing Degrees, TRUE
  2) T = True
  3) Bearing Degrees, Magnetic
  4) M = Magnetic
  5) TO Waypoint
  6) FROM Waypoint
  7) Checksum

Example 1: $GPBOD,099.3,T,105.6,M,POINTB,*01

Waypoint ID: "POINTB" Bearing 99.3 True, 105.6 Magnetic This sentence
is transmitted in the GOTO mode, without an active route on your
GPS. WARNING: this is the bearing from the moment you press enter in
the GOTO page to the destination waypoint and is NOT updated
dynamically! To update the information, (current bearing to waypoint),
you will have to press enter in the GOTO page again.

Example 2: $GPBOD,097.0,T,103.2,M,POINTB,POINTA*52

This sentence is transmitted when a route is active. It contains the
active leg information: origin waypoint "POINTA" and destination
waypoint "POINTB", bearing between the two points 97.0 True, 103.2
Magnetic. It does NOT display the bearing from current location to
destination waypoint! WARNING Again this information does not change
until you are on the next leg of the route. (The bearing from POINTA
to POINTB does not change during the time you are on this leg.)

------------------------------------------------------------------------------

 BWC - Bearing & Distance to Waypoint - Geat Circle
                                                         12
        1         2       3 4        5 6   7 8   9 10  11|    13 14
        |         |       | |        | |   | |   | |   | |    |   |
 $--BEC,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x.x,T,x.x,M,x.x,N,c--c,m,*hh<CR><LF>

 Field Number: 
  1) UTCTime
  2) Waypoint Latitude
  3) N = North, S = South
  4) Waypoint Longitude
  5) E = East, W = West
  6) Bearing, True
  7) T = True
  8) Bearing, Magnetic
  9) M = Magnetic
 10) Nautical Miles
 11) N = Nautical Miles
 12) Waypoint ID
 13) FAA mode indicator (NMEA 2.3 and later, optional)
 14) Checksum

Example 1: $GPBWC,081837,,,,,,T,,M,,N,*13

Example 2: GPBWC,220516,5130.02,N,00046.34,W,213.8,T,218.0,M,0004.6,N,EGLM*11

------------------------------------------------------------------------------

BWC - Bearing and Distance to Waypoint - Great Circle

         1          2     3    4     5  6  7  8  9  10 11 12  13
         |          |     |    |     |  |  |  |  |  |  |  |   |
 $--BWC,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x.x,T,x.x,M,x.x,N,nnn,*hh<CR><LF>

 Field number:
  1) UTC time of fix
  2) Latitude of waypoint
  3) N or S
  4) Longitude of waypoint
  5) W or E
  6) Bearing to waypoint, degrees true
  7) T indicating true bearing
  8) Bearing to waypoint, degrees magnetic
  9) M indicating magnetic
  10) Distance to waypoint, Nautical miles
  11) N indicating nautical miles
  12) Waypoint ID
  13) Checksum

Example 1: $GPBWC,225444,4917.24,N,12309.57,W,051.9,T,031.6,M,001.3,N,004*29

Example 2: $GPBWC,220516,5130.02,N,00046.34,W,213.8,T,218.0,M,0004.6,N,EGLM*11

------------------------------------------------------------------------------

 BWR - Bearing and Distance to Waypoint - Rhumb Line
                                                       11
        1         2       3 4        5 6   7 8   9 10  | 12   13
        |         |       | |        | |   | |   | |   | |    |
 $--BWR,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x.x,T,x.x,M,x.x,N,c--c*hh<CR><LF>

 Field Number: 
  1) UTCTime
  2) Waypoint Latitude
  3) N = North, S = South
  4) Waypoint Longitude
  5) E = East, W = West
  6) Bearing, True
  7) T = True
  8) Bearing, Magnetic
  9) M = Magnetic
 10) Nautical Miles
 11) N = Nautical Miles
 12) Waypoint ID
 13) Checksum

------------------------------------------------------------------------------

 BWW - Bearing - Waypoint to Waypoint

        1   2 3   4 5    6    7
        |   | |   | |    |    |
 $--BWW,x.x,T,x.x,M,c--c,c--c*hh<CR><LF>

 Field Number: 
  1) Bearing Degrees, TRUE
  2) T = True
  3) Bearing Degrees, Magnetic
  4) M = Magnetic
  5) TO Waypoint
  6) FROM Waypoint
  7) Checksum

------------------------------------------------------------------------------

 DBK - Depth Below Keel

        1   2 3   4 5   6 7
        |   | |   | |   | |
 $--DBK,x.x,f,x.x,M,x.x,F*hh<CR><LF>

 Field Number: 
  1) Depth, feet
  2) f = feet
  3) Depth, meters
  4) M = meters
  5) Depth, Fathoms
  6) F = Fathoms
  7) Checksum