Question

Can somebody help me or share some code about how to achieve GeoFencing on Windows Phone Mango.

I have list of GeoPositions(Latitude and Longitudes) and on every position update I want to verify that this current position is in that list which we in other words call GeoFencing, but i want to do it locally without touching any WebService etc…
So I want to know is it possible …

Also I want to achive this without blocking the main UI thread.

Please advice.

Answer 1

In the Microsoft sample form the Tidy app (part of the samples for Mango) – in Todo.DataAccess project, GeoCodeDistanceCalc static class which calculates the distance between a pair of co-ordinates with:

return radius * 2 * Math.Asin(Math.Min(1, Math.Sqrt((Math.Pow(Math.Sin((DiffRadian(lat1, lat2)) / 2.0), 2.0) + Math.Cos(ToRadian(lat1)) * Math.Cos(ToRadian(lat2)) * Math.Pow(Math.Sin((DiffRadian(lng1, lng2)) / 2.0), 2.0)))));

(where radius is the radius of the Earth in whatever unit you want the result)

For point in polygon approach, there is a whole Wikipedia article on the subject, but in the past, I’ve found the ray-casting algorithm relatively simple to implement.