在wp8 c＃中计算行驶距离最快的方法是什么？

Question

I am developing an application which shows driving distances to a certain points from current position of user. There are couple of thousands of coordinate points and the application needs to calculate the distance really fast. Below is the method I'm using.

public async Task<int> findRouteLength(System.Device.Location.GeoCoordinate currentPosition, System.Device.Location.GeoCoordinate businessPosition)
    {


        List<System.Device.Location.GeoCoordinate> routePositions = new List<System.Device.Location.GeoCoordinate>();
        routePositions.Add(currentPosition);
        routePositions.Add(businessPosition);
        RouteQuery query = new RouteQuery();
        query.TravelMode = TravelMode.Driving;
        query.Waypoints = routePositions;
        Route route = await query.GetRouteAsync();
        return route.LengthInMeters;

    }

However, this task can only calculate no more than 5-6 distances in one second. Is there any faster way of calculating driving distances in windows phone 8 c# ?

Answer 1

Try this, it should be much faster

public double CalculateDistance(System.Device.Location.GeoCoordinate geo, System.Device.Location.GeoCoordinate geo2)
{
    //var R = 6371; // result in km
    var R = 6371000; // result in m
    var dLat = (geo2.Latitude - geo.Latitude).ToRad();
    var dLon = (geo2.Longitude - geo.Longitude).ToRad();
    var lat1 = geo.Latitude.ToRad();
    var lat2 = geo2.Latitude.ToRad();

    var a = Math.Sin(dLat / 2) * Math.Sin(dLat / 2) +
            Math.Sin(dLon / 2) * Math.Sin(dLon / 2) * Math.Cos(lat1) * Math.Cos(lat2);
    var c = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));
    return R * c;
}

ToRad extension

static class Ext
{
    public static double ToRad(this double val)
    {
        return (Math.PI / 180) * val;
    }
}