County Maps US

Tools Distance, area and drive time

As the Crow Flies Distance

"As the crow flies" is the great-circle distance. This tool draws it next to the road route so the difference is visible, not just stated.

How to use it

  1. Enter the start and end points: addresses, cities or coordinates.
  2. Choose driving, cycling or walking for the road route.
  3. Press Compare. The straight line and the route are drawn in different colours with both distances and the detour percentage.

How it works

The crow-flies figure is the great-circle distance between the two coordinates, computed in the browser on a sphere of radius 6,371 km. The road figure is a route from the public Valhalla server on OpenStreetMap data at posted speeds with no traffic. Detour is the road distance divided by the straight-line distance, minus one.

If the routing server is busy or the two points are not connected by road, the straight-line result still shows and the status line says why the road figure is missing.

Questions

What does "as the crow flies" mean?
The shortest distance between two points over the surface of the Earth, ignoring roads, rivers and terrain, as if flying straight there. On a globe that is a great-circle arc.
How much longer is driving than the straight line?
Typically 15 to 30 percent in flat, gridded regions and 40 percent or more across mountains, bays and river valleys. This tool gives the actual percentage for your pair of points.
Can I use it for a flight?
The straight line is close to the great-circle route an aircraft would plan, but real flights add airway routing, weather diversions and holding, usually a few percent.

All map tools, free and without an account. Location data is processed in your browser and by the open geocoding services named on the sources page; nothing is stored by this site.