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Updated azimuthal projections

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ClemensFischer 2026-01-21 14:15:26 +01:00
parent 1bf4cab071
commit 2e27fc740d
5 changed files with 33 additions and 14 deletions
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18
MapControl/Shared/AzimuthalEquidistantProjection.cs
View file

@ -30,28 +30,36 @@ namespace MapControl
{
var p = GetProjectedPoint(latitude, longitude);
if (Math.Abs(p.CosC) >= 1d)
if (p.CosC == 1d)
{
return new Matrix(1d, 0d, 0d, 1d, 0d, 0d);
}
if (p.CosC == -1d)
{
return new Matrix(1d, 0d, 0d, double.PositiveInfinity, 0d, 0d);
}
var c = Math.Acos(p.CosC);
var k = c / Math.Sin(c); // p.195 (25-2)
var scale = new Matrix(1d, 0d, 0d, k, 0d, 0d); // h == 1
scale.Rotate(-Math.Atan2(p.Y, p.X) * 180d / Math.PI);
return scale;
return p.RelativeScale(1d, k);
}
public override Point? LocationToMap(double latitude, double longitude)
{
var p = GetProjectedPoint(latitude, longitude);
if (Math.Abs(p.CosC) >= 1d)
if (p.CosC == 1d) // p.195 "If cos c = 1, ... k' = 1, and x = y = 0."
{
return new Point();
}
if (p.CosC == -1)
{
return null; // p.195 "If cos c = -1, the point ... is plotted as a circle of radius πR."
}
var c = Math.Acos(p.CosC);
var k = c / Math.Sin(c); // p.195 (25-2)

18
MapControl/Shared/AzimuthalProjection.cs
View file

@ -1,4 +1,7 @@
using System;
#if WPF
using System.Windows.Media;
#endif
namespace MapControl
{
@ -32,10 +35,23 @@ namespace MapControl
var sinPhi1 = Math.Sin(phi1);
var cosLambda = Math.Cos(dLambda);
var sinLambda = Math.Sin(dLambda);
var cosC = sinPhi1 * sinPhi + cosPhi1 * cosPhi * cosLambda; // (5-3)
X = cosPhi * sinLambda;
Y = cosPhi1 * sinPhi - sinPhi1 * cosPhi * cosLambda;
CosC = sinPhi1 * sinPhi + cosPhi1 * cosPhi * cosLambda; // (5-3)
CosC = Math.Min(Math.Max(cosC, -1d), 1d); // protect against rounding errors
}
public Matrix RelativeScale(double radialScale, double perpendicularScale)
{
var scale = new Matrix(radialScale, 0d, 0d, perpendicularScale, 0d, 0d);
if (radialScale != perpendicularScale)
{
scale.Rotate(-Math.Atan2(Y, X) * 180d / Math.PI);
}
return scale;
}
}

4
MapControl/Shared/GnomonicProjection.cs
View file

@ -32,9 +32,7 @@ namespace MapControl
var k = 1d / p.CosC; // p.165 (22-3)
var h = k * k; // p.165 (22-2)
var scale = new Matrix(h, 0d, 0d, k, 0d, 0d);
scale.Rotate(-Math.Atan2(p.Y, p.X) * 180d / Math.PI);
return scale;
return p.RelativeScale(h, k);
}
public override Point? LocationToMap(double latitude, double longitude)

5
MapControl/Shared/OrthographicProjection.cs
View file

@ -29,11 +29,8 @@ namespace MapControl
public override Matrix RelativeScale(double latitude, double longitude)
{
var p = GetProjectedPoint(latitude, longitude);
var h = p.CosC; // p.149 (20-5)
var scale = new Matrix(h, 0d, 0d, 1d, 0d, 0d); // k == 1
scale.Rotate(-Math.Atan2(p.Y, p.X) * 180d / Math.PI);
return scale;
return p.RelativeScale(p.CosC, 1d); // p.149 (20-5), k == 1
}
public override Point? LocationToMap(double latitude, double longitude)

2
MapControl/Shared/StereographicProjection.cs
View file

@ -31,7 +31,7 @@ namespace MapControl
var p = GetProjectedPoint(latitude, longitude);
var k = 2d / (1d + p.CosC); // p.157 (21-4), k0 == 1
return new Matrix(k, 0d, 0d, k, 0d, 0d);
return p.RelativeScale(k, k);
}
public override Point? LocationToMap(double latitude, double longitude)