I've done this but in Java, probably you can port it to c# with no much effort.
This is very accurate for distances shorter than 2000 kilometers, then it can vary a little bit from the real distance. This is due to the earth curvature. But for small distances you can assume it is plain with none or very small impact in the result.
Here is a link I found useful.
And another link, an implementation of Haversine in C#.
Hope it helps.
Best regards, Federico.
public String execute(String plat1, String plon1, String plat2, String plon2) {
String distance;
double lat1, lon1, lat2, lon2;
try{
lat1 = Double.parseDouble(plat1);
lon1 = Double.parseDouble(plon1);
lat2 = Double.parseDouble(plat2);
lon2 = Double.parseDouble(plon2);
} catch (Exception e){
lat1 = 0.0d;
lon1 = 0.0d;
lat2 = 0.0d;
lon2 = 0.0d;
}
//theta and distance
double theta = lon1 - lon2;
double dist = Math.sin(deg2rad(lat1)) * Math.sin(deg2rad(lat2)) + Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) * Math.cos(deg2rad(theta));
//distance
dist = Math.acos(dist);
dist = rad2deg(dist);
dist = dist * 60 * 1.1515;
dist = dist * 1.609344;
//convert to meters
dist = dist * 1000;
//output in meters
distance = Double.toString(dist);
return distance;
}
private double deg2rad(double deg) {
return (deg * Math.PI / 180.0);
}
private double rad2deg(double rad) {
return (rad * 180.0 / Math.PI);
}
A little explanation:
- (plat1, plon1) is lat and lng of point 1 or origin
- (plat2, plon2) is lat and lng of point 2 or destination
- the method "execute" is the one you call, it returns a string containing the distance in meters (conversion to other units can be done easily)
- two assisting functions are declared as "deg2rad" and "rad2deg".