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I am going to design an Android application and I will be needing the distances of the pathways inside our university(pathways between buildings)

I read about OSM(OpenStreetMap) and tried it. It is a map which is editable which means anyone can contribute to that map(like a wikipedia map version).

It has many routing services that give routes and directions between two point(start and end).

There is a routing service named GraphHopper and it is very easy to use. I can just drag and drop the start and end pt and it gives the distance(km) between the two pts.

What I want to know is how did they come up with the distance?

Is the distance reliable and accurate?

Any help is greatly appreciated because I want to use the distances for my Android app and I need to know if these distances have basis.

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The distance is 'accurate' in the sense that it correctly processes the existing information from OpenStreetMap and correctly adds road segments for the final route. You can just try for your local area and compare to your own knowledge.

There could be mapping errors, where a road is incorrectly mapped. And there could be also roads missing and so the router uses a detour making the path unnecessarily longer. Also there are different modes like for cars or bikes or fastest and shortest where you get a different distance between two coordinates.

Karussell
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  • Thanks for the answer? Yes, it is processed from OSM because it is a routing service for it. However, how did OSM come up with those distances? Did they use satellite? What is their basis for rendering the distances –  Nov 20 '14 at 12:36
  • The basis is different. Some mapper use fieldwork and gpx tracker others use satellite. But due to coordinate systems transformations and other math everything should be consistent. If not, its a bug ;). So from e.g. two GPS coordinates you can calculate the distance rather precise via haversine formular – Karussell Nov 21 '14 at 09:41