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Positioning Application: What is the format of the GPS legacy navigation data binary dump file?

  • PosApp (SimGEN / SimREPLAYplus / SimREPLAY)
  • GPS navigation data
  1. Go to menu [Options-->General Options]
  2. Enable "Dump navigation data"
  3. Run the scenario (normal speed or turbo speed)
  4. For GPS legacy navigation data, PosApp creates a binary file called "Nav_dump.bin"

You can decode the binary file using the "GPS L1C/A Nav Data Extract" utility via menu [Tools-->General Utilities]

But to decode the binary file for yourself:-

  1. The Nav_dump.bin file is essentially just a sequence of "records" each containing
        - the time into the run
        - the satellite id
        - the nav bits for a sub-frame of GPS Nav Data (6s).
  2. A set of data "records" is written for all enabled GPS satellites every 6s in the run.
  3. Each "record" is defined as follows:
                    struct Bin_nav_data
                        int run_time_secs_i;
                        unsigned char sat_id;
                        unsigned char nav_bits[60];
  4. The file is opened as follows:
                    std::string &bin_file_name=< insert file name here (Nav_dump.bin) with path as required >;
                    FILE *in_file_ptr;
                    in_file_ptr = fopen( bin_file_name.c_str() );
  5. Each sub-frame of nav data is read using:
                    Bin_nav_data data;
                    fread( &data, sizeof(data), 1, in_file_ptr );
  6. The 60 bytes of the nav_bits array are in chronological order, i.e data.nav_bit[0] is transmitted first.
  7. Each byte (char) of nav_bits contains 5 bits of Nav Data.
        - These occupy the MS locations such that bit7 is the first to be transmitted and bit 3 the last. (Bits 2 to 0 are unused).

Product : Nav Data Decoder,SimREPLAYplus,SimREPLAY,SimGEN,PosApp,Navigation Data,GPS