User’s Manual INNOMAR Parametric Sub-Bottom Profilers / SESWIN 213
Innomar Technologie GmbH (2023-01) 213
A.18 (GNSS) NMEA Sentences
In this section NMEA 0183 sentences often used by GNSS receivers are given for reference.
Some more NMEA sentences, related to motion sensors, are described in section A.19 on page
215.
In general, each sentence is ASCII data and consists of a dollar sign ($), two letters to identify
the sender (talker ID), three letters naming the data set (sentence ID), the sentence data itself,
an optional checksum (*cc), followed by carriage return and line feed ASCII symbols (<CR><LF>,
0D0Ah). The checksum is calculated by exclusive-ORing (XOR) all characters between the ‘$’
and the ‘*’ characters and formatted as HEX value.
A detailed, but rather technical description of the NMEA 0183 standard can be found at this web
site: https://gpsd.gitlab.io/gpsd/NMEA.html
GGA (Global Positioning System Fix Data)
GGA,HHMMSS.ss,DDMM.mm,a,DDDMM.mm,a,Q,SS,x.x,h.h,m,x.x,m,t.t,nn*cc<CR><LF>
Ex $GPGGA,145502.40,5406.62680,N,01204.13713,E,2,05,2.9,22.08,M,38.87,M,4,0000*67
1 UTC of position fix
2 Latitude (DD degrees, MM,mm minutes)
3 ‘N’ or ‘S’ (North or South) hemisphere
4 Longitude (DD degrees, MM,mm minutes)
5 ‘E’ or ‘W’ (East or West) hemisphere
6 Quality indicator (0: invalid; 1: GPS; 2: diff. GPS; 3: GPS PPS; 4: RTK; 5: float RTKt;
6: estimated; 7: manual input; 8: simulation mode)
7 Number of satellites in use (00 – 12)
8 Horizontal dilution of precision (HDOP in meters)
9 Antenna altitude above/below mean sea level (geoid) in meters
10 ‘M’ (Antenna height unit, meters)
11 Geoidal separation (Diff. between WGS-84 earth ellipsoid and mean sea level.)
12 ‘M’ (Units of geoidal separation, meters)
13 Age of differential position data in seconds (time since last update from diff. reference station)
14 Diff. reference station ID (0000 – 1023)
ZDA (Time & Date)
,dd,mm,yyyy,xx,xx*cc<CR><LF>
Ex $GPZDA,145502.40,04,01,2007,+00,00*4E
1 UTC time
2 Day of month (1 ... 31)
3 Month of year (1 ... 12)
4 Year (4 digits)
5 Local zone hours description (00 ... +-13 hours)
6 Local zone minutes description (00 ... 59), apply same sign as local hours
VTG (Actual track made good and speed over ground)
VTG,cc.cc,T,cc.cc,M,ss.ss,N,ss.ss,K*cc<CR><LF>
Ex $GPVTG,187.08,T,185.22,M,000.07,N,000.12,K,D*28
1 Course over ground in degrees, true
2 'T' indicates that course is relative to true North
3 Course over ground in degrees, magnetic; often not used
4 'M' indicates that course is relative magnetic North; often not used
5 Speed over ground in knots
6 'N' indicates that speed over ground in in knots
7 Speed over ground in kilometers/hour
8 'K' indicates that speed over ground is in kilometers/hour
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