NMEA-0183 protocols in my eyes

NMEA is the abbreviation of National Marine Electronics Association (National Maritime Electronics Association. The Association is a private institution dedicated to research on marine electronic devices and has developed NMEA standards for communication interfaces and protocols between GPS (GPS) electronic devices. NMEA-0183 protocol is currently the most widely used protocol on GPS receivers, most common GPS receivers, GPS data processing software, navigation software are complying with or at least compatible with this Protocol. I. Electrical featuresBaud Rate: 4800 bpsdata bits: 8 (D7 = 0) Parity: nonestop bits: one (or more) Ii. Agreement 1. Syntax formatThe format of NMEA 0183 is generally as follows: $ AAAAA, DF1, df2 ,.... [Cr] [LF] All Information starts from $ and ends with a line break. The basic types of information are explained with the five characters after $. Multiple parameters are separated by commas. 2. protocol typeThere are three basic protocol types in NMEA 0183: a) Information Source B) query c) attributes 1) Information SourceStandard Format: $ ttsss, DF1, df2 ,.... [Cr] [LF] the last three characters followed by $ are used to identify the last three characters used as the Information Content identifier. The information identifier defines the reserved data zone. Under the NMEA 0183 standard, the Information Content of each type of data zone complies with the standard. For example, $ hchdm, 238, M [Cr] [LF] indicates "HC" indicates that the source of information is used as a magnetic compass. "HDM" indicates that the following is the first course of the magnetic ship, 238 indicates the value of the first course and M indicates that the value of the first course is magnetic. 2) QueryThe standard format is $ ttlscsi, SSS, [Cr] [LF]. The first two characters are used as the identifier of the requester's information source, and the last two characters are used as the Information Identification of the device to be queried, the last character indicates that this is a query information. The following field (SSS) contains the memory information of the content to be queried in three words. Query means that the receiver needs to get a regular content from the information source, for example, we can send a message to the GPS receiver request to send a "DISTANCE-TO-WAYPOINT" information, after receiving a response, the GPS receiver sends the request content until it receives another request. For example, $ ccgpq, GGA [Cr] [LF] indicates that the "cc" device (Computer) is querying GGA content from the "GP" device (GPS. GPS sends this content every second until there are other query requests. 3) attributesThis is a method for the vendor to use special content that is not predefined under the standard. The common format is $ pmmma, DF1, df2 ,..., [Cr] [LF] P description is the property content, mmm is defined as the vendor information code, a (A-Z) indicates the information type. The NMEA-0183 Protocol defines a lot of statements, but the commonly used or most compatible statements are only $ gpgga, $ gpgsa, $ gpgsv, $ gwmc, $ gpvtg, $ gpgll and so on. 3. protocol syntax 1) Global Positioning System Fix Data (GGA) GPS Positioning Information$ Gpgga, <1 >,< 2 >,< 3 >,< 4 >,< 5 >,< 6 >,< 7 >,< 8 >,< 9>, m, <10>, M, <11>, <12> * hh <CR> <LF> <1> UTC time, hhmmss (hour/minute/second) format <2> latitude ddmm. mmmm (degree) format (the preceding 0 will also be transmitted) <3> latitude hemisphere N (northern hemisphere) or S (Southern Hemisphere) <4> longitude dddmm. mmmm (degree) format (the preceding 0 will also be transmitted) <5> longitude hemisphere E (eastern longitude) or W (Western longitude) <6> GPS status: 0 = undetermined, 1 = non-differential positioning, 2 = differential positioning, 6 = estimated number of satellites using the resolution position (00 ~ 12) (the preceding 0 will also be transmitted) <8> hdop horizontal precision factor (0.5 ~ 99.9) <9> altitude (-9999.9 ~ 99999.9) <10> height of the earth's elliptical sphere relative to the geolevel <11> differential time (the number of seconds since the last receipt of the differential signal, if it is not a differential positioning, it will be blank <12> ID number of the differential substation 0000 ~ 1023 (the previous 0 will also be transmitted, if not differential positioning will be blank) 2) gps dop and active satellites (GSA) current satellite information$ Gpgsa, <1 >,< 2 >,< 3 >,< 3 >,< 3 >,< 3 >,< 3 >,< 3 >,< 3>, <3>, <3>, <3>, <3>, <3>, <4>, <5>, <6> * hh <CR> <LF>
<1> mode, M = manual, a = automatic
<2> positioning type, 1 = No positioning, 2 = 2D positioning, 3 = 3D Positioning
<3> PRN code (Pseudo-Random Noise Code), which is used to calculate the satellite number (01 ~ 32 ).
<4> position precision factor of pdop (0.5 ~ 99.9)
<5> hdop horizontal precision factor (0.5 ~ 99.9)
<6> vdop vertical precision factor (0.5 ~ 99.9) 3) GPS satellites in view (GSV) Visible satellite information$ Gpgsv, <1>, <2>, <3>, <4>, <5>, <6>, <7> ,... <4>, <5>, <6>, <7> * hh <CR> <LF>
<1> total number of GSV statements
<2> the number of GSV in this sentence
<3> total number of visible satellites (00 ~ 12, the previous 0 will also be transmitted)
<4> PRN code (Pseudo-Random Noise Code) (01 ~ 32, the previous 0 will also be transmitted)
<5> satellite elevation (00 ~ 90 degrees, the previous 0 will also be transmitted)
<6> satellite azimuth (000 ~ 359 degrees, the previous 0 will also be transmitted)
<7> signal-to-noise ratio (00 ~ 99db. If no satellite is tracked, the preceding 0 will be transmitted)
Note: <4>, <5>, <6>, <7> information is displayed cyclically based on each satellite. Each GSV statement can display up to four satellites. Other satellite information will be output in the next series of nmea0183 statements. 4) recommended minimum specific GPS/transit data (RMC) recommended location information$ Uplmc, <1>, <2>, <3>, <4>, <5>, <6>, <7>, <8>, <9>, <10>, <11>, <12> * hh <CR> <LF>
<1> UTC time, hhmmss (hour/minute/second) Format
<2> positioning status, A = valid, V = invalid
<3> latitude ddmm. Mmmm (degree) format (the preceding 0 will also be transmitted)
<4> latitude hemisphere N (northern hemisphere) or S (Southern Hemisphere)
<5> longitude dddmm. Mmmm (degree) format (the preceding 0 will also be transmitted)
<6> longitude hemisphere E (eastern longitude) or W (Western longitude)
<7> ground speed (000.0 ~ Section 999.9, the previous 0 will also be transmitted)
<8> ground heading (000.0 ~ 359.9 degrees. Based on the reference of zhenbei, the preceding 0 will also be transmitted)
<9> UTC date, in ddmmyy format
<10> magnetic angle (000.0 ~ 180.0 degrees, the previous 0 will also be transmitted)
<11> magnetic angle direction, E (East) or W (West)
<12> mode indication (output only in nmea0183 3.00, A = self-locating, D = differential, E = estimation, n = Invalid Data) 5) track made good and ground speed (Vtg) ground speed information$ Gpvtg, <1>, T, <2>, M, <3>, N, <4>, K, <5> * hh <CR> <LF>
<1> ground heading based on zhenbei (000 ~ 359 degrees, the previous 0 will also be transmitted)
<2> ground heading (000 ~ 359 degrees, the previous 0 will also be transmitted)
<3> ground speed (000.0 ~ Section 999.9, the previous 0 will also be transmitted)
<4> ground speed (0000.0 ~ 1851.8 km/hour, the front 0 will also be transmitted)
<5> mode indication (output only in nmea0183 3.00, A = self-locating, D = differential, E = estimation, n = Invalid Data) 6) geographic position (GlL) Location Geographic Information$ Gpgll, <1 >,< 2 >,< 3 >,< 4 >,< 5 >,< 6 >,< 7> * hh <CR> <LF>
<1> latitude ddmm. Mmmm (degree) format (the preceding 0 will also be transmitted)
<2> latitude hemisphere N (northern hemisphere) or S (Southern Hemisphere)
<3> longitude dddmm. Mmmm (degree) format (the preceding 0 will also be transmitted)
<4> longitude hemisphere E (eastern longitude) or W (Western longitude)
<5> UTC time, hhmmss (hour/minute/second) Format
<6> positioning status. A = valid and V = invalid
<7> mode indication (output only in nmea0183 3.00, A = self-locating, D = differential, E = estimation, n = Invalid Data)