NEMA stream RTK

shane · September 16, 2022, 10:44pm

When we configure a serial port on the cube (SERIALx_PROTOCOL) to output a NEMA GPS stream (20), is that stream corrected when the system is running an RTK setup?

If not, does anyone know how we might go about doing this? We’re looking to use the NEMA stream for Georeferrencing images from a sensor, but need them RTK corrected when the RTK system is in use.

Michael_Oborne · September 18, 2022, 12:11am

looking at the code

github.com

ArduPilot/ardupilot/blob/6b962ae48bdbee887317b4ebcd324b0d482c6ee9/libraries/AP_NMEA_Output/AP_NMEA_Output.cpp#L100

      
        
            snprintf(tstring, sizeof(tstring), "%02u%02u%06.3f", tm->tm_hour, tm->tm_min, tm->tm_sec + (time_usec % 1000000) * 1.0e-6);
            
            
// format date string
            char dstring[7];
            snprintf(dstring, sizeof(dstring), "%02u%02u%02u", tm->tm_mday, tm->tm_mon+1, tm->tm_year % 100);
            
            
auto &ahrs = AP::ahrs();
            
            
// get location (note: get_location from AHRS always returns true after having GPS position once)
            Location loc;
            bool pos_valid = ahrs.get_location(loc);
            
            
// format latitude
            char lat_string[13];
            float deg = fabsf(loc.lat * 1.0e-7f);
            snprintf(lat_string,
                     sizeof(lat_string),
                     "%02u%08.5f,%c",
                     (unsigned) deg,
                     double((deg - int(deg)) * 60),
                     loc.lat < 0 ? 'S' : 'N');

the position is the ekf derived location… ie if you had rtk lock at the time, then it is likerly to be a rtk inertial location. so i believe it is what your looking for.