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Revised Location calculations

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ClemensFischer 2025-03-10 15:47:33 +01:00
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commit 3c88a81b0d
6 changed files with 64 additions and 101 deletions
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MapControl/Shared/Location.cs
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@ -5,6 +5,10 @@ namespace MapControl
{
/// <summary>
/// A geographic location with latitude and longitude values in degrees.
/// For calculations with azimuth and distance on great circles, see
/// https://en.wikipedia.org/wiki/Great_circle
/// https://en.wikipedia.org/wiki/Great-circle_distance
/// https://en.wikipedia.org/wiki/Great-circle_navigation
/// </summary>
#if UWP || WINUI
[Windows.Foundation.Metadata.CreateFromString(MethodName = "Parse")]
@ -81,54 +85,63 @@ namespace MapControl
}
/// <summary>
/// Calculates the great circle distance between this and the specified Location.
/// https://en.wikipedia.org/wiki/Great_circle
/// https://en.wikipedia.org/wiki/Great-circle_distance
/// https://en.wikipedia.org/wiki/Great-circle_navigation
/// Calculates great circle azimuth and distance in radians between this and the specified Location.
/// </summary>
public double GetDistance(
Location location, double earthRadius = MapProjection.Wgs84EquatorialRadius)
public void GetAzimuthDistance(Location location, out double azimuth, out double distance)
{
var lat1 = Latitude * Math.PI / 180d;
var lon1 = Longitude * Math.PI / 180d;
var lat2 = location.Latitude * Math.PI / 180d;
var lon2 = location.Longitude * Math.PI / 180d;
var sinLat1 = Math.Sin(lat1);
var cosLat1 = Math.Cos(lat1);
var sinLat2 = Math.Sin(lat2);
var sinLat1 = Math.Sin(lat1);
var cosLat2 = Math.Cos(lat2);
var sinLon12 = Math.Sin(lon2 - lon1);
var sinLat2 = Math.Sin(lat2);
var cosLon12 = Math.Cos(lon2 - lon1);
var a = cosLat1 * sinLat2 - sinLat1 * cosLat2 * cosLon12;
var b = cosLat2 * sinLon12;
var c = sinLat1 * sinLat2 + cosLat1 * cosLat2 * cosLon12;
var s12 = Math.Atan2(Math.Sqrt(a * a + b * b), c);
return earthRadius * s12;
var sinLon12 = Math.Sin(lon2 - lon1);
var a = cosLat2 * sinLon12;
var b = cosLat1 * sinLat2 - sinLat1 * cosLat2 * cosLon12;
// α1
azimuth = Math.Atan2(a, b);
// σ12
distance = Math.Atan2(Math.Sqrt(a * a + b * b), sinLat1 * sinLat2 + cosLat1 * cosLat2 * cosLon12);
}
/// <summary>
/// Calculates the Location on a great circle at the specified azimuth angle and distance from this Location.
/// https://en.wikipedia.org/wiki/Great_circle
/// https://en.wikipedia.org/wiki/Great-circle_navigation
/// Calculates the great circle distance in meters between this and the specified Location.
/// </summary>
public Location GetLocation(
double azimuth, double distance, double earthRadius = MapProjection.Wgs84EquatorialRadius)
public double GetDistance(Location location, double earthRadius = MapProjection.Wgs84EquatorialRadius)
{
GetAzimuthDistance(location, out double _, out double distance);
return earthRadius * distance;
}
/// <summary>
/// Calculates the Location on a great circle at the specified azimuth and distance in radians from this Location.
/// </summary>
public Location GetLocation(double azimuth, double distance)
{
var s12 = distance / earthRadius;
var az1 = azimuth * Math.PI / 180d;
var lat1 = Latitude * Math.PI / 180d;
var lon1 = Longitude * Math.PI / 180d;
var sinS12 = Math.Sin(s12);
var cosS12 = Math.Cos(s12);
var sinAz1 = Math.Sin(az1);
var cosAz1 = Math.Cos(az1);
var sinLat1 = Math.Sin(lat1);
var cosD = Math.Cos(distance);
var sinD = Math.Sin(distance);
var cosA = Math.Cos(azimuth);
var sinA = Math.Sin(azimuth);
var cosLat1 = Math.Cos(lat1);
var lat2 = Math.Asin(sinLat1 * cosS12 + cosLat1 * sinS12 * cosAz1);
var lon2 = lon1 + Math.Atan2(sinS12 * sinAz1, cosLat1 * cosS12 - sinLat1 * sinS12 * cosAz1);
var sinLat1 = Math.Sin(lat1);
var lat2 = Math.Asin(sinLat1 * cosD + cosLat1 * sinD * cosA);
var lon2 = lon1 + Math.Atan2(sinD * sinA, cosLat1 * cosD - sinLat1 * sinD * cosA);
return new Location(lat2 * 180d / Math.PI, lon2 * 180d / Math.PI);
}
/// <summary>
/// Calculates the Location on a great circle at the specified azimuth in degrees and distance in meters from this Location.
/// </summary>
public Location GetLocation(double azimuth, double distance, double earthRadius = MapProjection.Wgs84EquatorialRadius)
{
return GetLocation(azimuth * Math.PI / 180d, distance / earthRadius);
}
}
}