Summary: Calculate distance and azimuth Operation ID: getDistAz Auth: none
Calculate the great-circle distance and azimuth between two geographic points on Earth. This endpoint performs the fundamental geospatial computation needed in seismology: determining how far an earthquake (event) is from a seismic station, and the direction from each point to the other. Returns an XML document containing the azimuth (direction from station to event), back azimuth (direction from event to station), and distance in both degrees (angular distance) and kilometers (great-circle distance). Use this when you need to compute station-event geometries for earthquake location studies, travel time analysis, or seismic network planning.
Original spec description
Calculate distance, azimuth, and back-azimuth between two geographic points using the WGS84 ellipsoid.
Usage Tips
- All four parameters (evtlat, evtlon, stalat, stalon) are required
- Coordinates must be in decimal degrees (WGS84 datum)
- Latitude range: -90 to 90 (negative for Southern Hemisphere)
- Longitude range: -180 to 180 (negative for West)
- For local distances, expect small azimuth values; for teleseismic events, distances approach 180 degrees
- The distance in kilometers is the great-circle distance (shortest path on a sphere)
Parameters (4)
evtlat(number, query, optional)
Event latitude in decimal degrees
Constraints: {'minimum': -90, 'maximum': 90}
evtlon(number, query, optional)
Event longitude in decimal degrees
Constraints: {'minimum': -180, 'maximum': 180}
stalat(number, query, optional)
Station latitude in decimal degrees
Constraints: {'minimum': -90, 'maximum': 90}
stalon(number, query, optional)
Station longitude in decimal degrees
Constraints: {'minimum': -180, 'maximum': 180}
Examples (4)
Title
Type
URL
Action
Regional distance calculation - California event to LA station