Returns the geomagnetic field for a location at the specified date.
int wmm_get_geomagnetic_field(const wmm_location_t *loc, const struct tm *date, wmm_geomagnetic_field_t *field)
The geographic location to be used in the calculation of the magnetic field.
The date to be used in the calculation of the magnetic field.
The geomagnetic field for the given location and date.
The geomagnetic field is returned in field.
If the latitude_deg or longitude_deg values in loc exceed their ranges, they will be changed to fit into their respective range.
0 if successful, -1 if an error occurred, 1 if loc was altered to fit into the magnetic model range.