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Reworked azimuthal projections

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ClemensFischer 2026-01-19 21:38:18 +01:00
parent 19cba8978b
commit 2c9e478095
6 changed files with 117 additions and 107 deletions
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35
MapControl/Shared/StereographicProjection.cs
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@ -11,7 +11,7 @@ namespace MapControl
/// Spherical Stereographic Projection - AUTO2:97002.
/// See "Map Projections - A Working Manual" (https://pubs.usgs.gov/publication/pp1395), p.157-160.
/// </summary>
public class StereographicProjection : MapProjection
public class StereographicProjection : AzimuthalProjection
{
public const string DefaultCrsId = "AUTO2:97002"; // GeoServer non-standard CRS identifier
@ -22,38 +22,31 @@ namespace MapControl
public StereographicProjection(string crsId)
{
Type = MapProjectionType.Azimuthal;
CrsId = crsId;
}
public double EarthRadius { get; set; } = Wgs84MeanRadius;
public override Point RelativeScale(double latitude, double longitude)
{
(var cosC, var _, var _) = GetPointValues(latitude, longitude);
var k = 2d / (1d + cosC); // p.157 (21-4), k0 == 1
return new Point(k, k);
}
public override Point? LocationToMap(double latitude, double longitude)
{
if (Center.Equals(latitude, longitude))
{
return new Point();
}
(var cosC, var x, var y) = GetPointValues(latitude, longitude);
var k = 2d / (1d + cosC); // p.157 (21-4), k0 == 1
Center.GetAzimuthDistance(latitude, longitude, out double azimuth, out double distance);
var mapDistance = Math.Tan(distance / 2d) * 2d * EarthRadius;
return new Point(mapDistance * Math.Sin(azimuth), mapDistance * Math.Cos(azimuth));
return new Point(EarthRadius * k * x, EarthRadius * k * y); // p.157 (21-2/3)
}
public override Location MapToLocation(double x, double y)
{
if (x == 0d && y == 0d)
{
return new Location(Center.Latitude, Center.Longitude);
}
var rho = Math.Sqrt(x * x + y * y);
var c = 2d * Math.Atan(rho / (2d * EarthRadius)); // p.159 (21-15), k0 == 1
var azimuth = Math.Atan2(x, y);
var mapDistance = Math.Sqrt(x * x + y * y);
var distance = 2d * Math.Atan(mapDistance / (2d * EarthRadius));
return Center.GetLocation(azimuth, distance);
return GetLocation(x, y, rho, Math.Sin(c));
}
}
}