The distance-azimuth service will calculate the great-circle angular distance, azimuth, and backazimuth between two geographic coordinate pairs. All results are reported in degrees, with azimuth and backazimuth measured clockwise from North.
The azimuth is the angle from the station to the event, while the backazimuth is the angle from the event to the station.
Latitudes are converted to geocentric latitudes using the WGS84 spheroid to correct for ellipticity.
The results are returned in a simple XML format.