RTKLib_RTCM_MSM_Extraction

Too many GNSS observations will increase the pressure on network transmission. It is inconvenient to directly configure the receiver to obtain the required observations. For example, for a set of GNSS observations at GPS L1/L2 frequencies, you only need the L1 frequency, and it is inconvenient to directly configure the tracking mode of the receiver. A can be used to extract frequency-specific observations from RTCM packets and reassemble them into RTCM MSM without affecting the decoding of RTCM MSM.

Function interface and parameters

API_DECLSPEC int rtcmCvt(int sync,unsigned char *buff_in,int len,char **freq_c,unsigned char *buff_sd,int *len_sd);

args:

• I uint8_t *buff_in rtcm binary data
• I int len length of received rtcm data
• I char **freq_c sent frequency
• O uint8_t *buff_sd converted rtcm data (need to be sent)
• O int *len_sd results length
• return : status (1:ok; 0,-1:error or no rtcm data)

freq_c selection :

• GPS："L1", "L2", "L5",
• GLONASS： "G1", "G2", "G3", "G1a","G2a",
• Galileo： "E1", "E5b","E5a","E6", "E5ab",
• QZSS： "L1", "L2", "L5", "L6",
• SBAS： "L1", "L5",
• BDS： "B1I","B3I","B2a","B1C","B2ab","B2I", "B2b",
• IRNSS： "L5", "S",

freq_c format

char *freq_c[7]={
                  "L1",                     //GPS
                  "",                       //GLONASS
                  "E1+E5b",                 //Galileo
                  "L1+L2",                  //QZSS
                  "L1+L5",                  //SBAS
                  "B1I+B2I+B3I",            //BDS
                  "L5+S"                    //IRN
                  };

note:

Taking the above as an example, the rtcm data will be encoded:

• GPS L1 data will be obtained, while the corresponding L2 and L3 are discarded.
• GLONASS no data will be sent;
• BDS B1I, B2I, B3I will be obtained in new rtcm buff.
• "G3", "G1a","G2a" in RTCM ICD are not provided. therefore, please do not choose the three.