Functions:-Code shared between low-level and high-level interfaces. Most of them do exactly what they say on the tin. Notes based on code as of Mon Apr 5 21:38:06 2010 -0400. void gps_clear_fix(struct gps_fix_t *fixp) Stuff a fix structure with recognizable out-of-band values. unsigned int gps_valid_fields(struct gps_fix_t *fixp) Clears certain status flags, depending if the associated fields are invalid. double timestamp(void) Returns the number of seconds and microseconds since the UNIX Epoch (00:00:00 UTC, January 1, 1970); i.e. a unique value which can be used to timestamp any event. time_t mkgmtime(register struct tm *t) Convert a struct tm {} (see time.h) to seconds since UNIX Epoch. double iso8601_to_unix(char *isotime) Convert an ISO8601 UTC string (like 2006-01-25T13:15:22.9) to Unix UTC. char *unix_to_iso8601(double fixtime, char isotime[], int len) Reverse of the above, no timezone adjustment. double gpstime_to_unix(int week, double tow) Convert gps time to UNIX time, allowing for the gps week number rollover. void unix_to_gpstime(double unixtime, int *week, double *tow) Reverse of the above. static double CalcRad(double lat) Return the earth's radius of curvature in meters at specified latitude. double earth_distance(double lat1, double lon1, double lat2, double lon2) Return the distance in meters between two points specified in degrees. static int invert(double mat[4][4], double inverse[4][4]) Try and invert an array. If it is possible, fill the inverted array and return a 1. Return a 0 if it is not possible. gps_mask_t dop(struct gps_data_t *gpsdata) Take a gps data structure and try to calculate the DOP values from the other data in it. Return 0 if it is not possible or update the appropriate DOP fields in the structure and set a mask which tells which fields were updated.