Geolocation: Tutorial on plotting numerous users on map?

Can someone can refer me to a tutorial or such that provides information regarding how to capture a users location and plot other users around them? I'm hoping to build an app that contains a functionality for you to open the app on the phone and see other users within a set radius that are also running the app. All help开发者_高级运维 is greatly appreciated. Thanks for your time and assistance.

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You could use node.js. There is a screencast (not free) about how to do exactly such a thing: http://peepcode.com/products/nodejs-i

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It is very hard to help without knowing which programming language you are interested in.

But here goes a page for an example that uses python and javascript:

http://www.goldb.org/geo_maps/