Jason N. Gaylord Jason N. Gaylord - 1 year ago 176
C# Question

Calculating Distance between two Latitude and Longitude GeoCoordinates

I'm calculating the distance between two GeoCoordinates. I'm testing my app against 3-4 other apps. When I'm calculating distance, I tend to get an average of 3.3 miles for my calculation whereas other apps are getting 3.5 miles. It's a big difference for the calculation I'm trying to perform. Are there any good class libraries out there for calculating distance? I'm calculating it like this in C#:

public static double Calculate(double sLatitude,double sLongitude, double eLatitude,
double eLongitude)
var sLatitudeRadians = sLatitude * (Math.PI / 180.0);
var sLongitudeRadians = sLongitude * (Math.PI / 180.0);
var eLatitudeRadians = eLatitude * (Math.PI / 180.0);
var eLongitudeRadians = eLongitude * (Math.PI / 180.0);

var dLongitude = eLongitudeRadians - sLongitudeRadians;
var dLatitude = eLatitudeRadians - sLatitudeRadians;

var result1 = Math.Pow(Math.Sin(dLatitude / 2.0), 2.0) +
Math.Cos(sLatitudeRadians) * Math.Cos(eLatitudeRadians) *
Math.Pow(Math.Sin(dLongitude / 2.0), 2.0);

// Using 3956 as the number of miles around the earth
var result2 = 3956.0 * 2.0 *
Math.Atan2(Math.Sqrt(result1), Math.Sqrt(1.0 - result1));

return result2;

What could I be doing wrong? Should I calculate it in km first and then convert to miles?

Answer Source

The GeoCoordinate class (.NET Framework 4 and higher) already has GetDistanceTo method.

var sCoord = new GeoCoordinate(sLatitude, sLongitude);
var eCoord = new GeoCoordinate(eLatitude, eLongitude);

return sCoord.GetDistanceTo(eCoord);

The distance is in meters.

You need to reference System.Device.

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