Apps calculate all points in radius of (lat,long)

[tom21]

Say i provide (x,y) latitude and longitude, and a radius of 500m.

what i would like to achieve with the help of Google maps api is that when user is outside 500m of (x,y), i want to trigger action such as send email.

How can i set radius in meter,kilometre?

 

[IrvineCAGuy]

You will need to compute the distance taking into account the curvature of the earth. The formula is complex. A simplified method can be demonstrated at:

http://www.geodatasource.com/developers/java
or this
Distance between two GPS coordinates (in meter) - Android Snippets

Good luck.