Updated MapProjection and MapGraticule

2026-04-08 16:05:50 +00:00 · 2026-02-01 01:42:24 +01:00 · 2026-02-01 01:42:24 +01:00 · cfed3575ac
commit cfed3575ac
parent 2a45c1165c
16 changed files with 392 additions and 355 deletions
--- a/MapControl/Shared/StereographicProjection.cs
+++ b/MapControl/Shared/StereographicProjection.cs
@ -0,0 +1,97 @@
+using System;
+using System.Globalization;
+#if WPF
+using System.Windows;
+using System.Windows.Media;
+#elif AVALONIA
+using Avalonia;
+#endif
+
+namespace MapControl
+{
+    /// <summary>
+    /// 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 const string DefaultCrsId = "AUTO2:97002"; // GeoServer non-standard CRS identifier
+
+        public StereographicProjection(double centerLongitude, double centerLatitude, string crsId = DefaultCrsId)
+        {
+            CentralMeridian = centerLongitude;
+            LatitudeOfOrigin = centerLatitude;
+            CrsId = string.Format(CultureInfo.InvariantCulture,
+                "{0},1,{1:0.########},{2:0.########}", crsId, centerLongitude, centerLatitude);
+        }
+
+        public override double GridConvergence(double latitude, double longitude)
+        {
+            var p0 = LocationToMap(latitude, longitude);
+            var p1 = LocationToMap(latitude + 1e-3, longitude);
+
+            return Math.Atan2(p0.X - p1.X, p1.Y - p0.Y) * 180d / Math.PI;
+        }
+
+        public override Matrix RelativeTransform(double latitude, double longitude)
+        {
+            return new Matrix(1d, 0d, 0d, 1d, 0d, 0d);
+        }
+
+        public override Point LocationToMap(double latitude, double longitude)
+        {
+            var phi = latitude * Math.PI / 180d;
+            var phi1 = LatitudeOfOrigin * Math.PI / 180d;
+            var dLambda = (longitude - CentralMeridian) * Math.PI / 180d; // λ - λ0
+            var cosPhi = Math.Cos(phi);
+            var sinPhi = Math.Sin(phi);
+            var cosPhi1 = Math.Cos(phi1);
+            var sinPhi1 = Math.Sin(phi1);
+            var cosLambda = Math.Cos(dLambda);
+            var sinLambda = Math.Sin(dLambda);
+            var x = cosPhi * sinLambda;
+            var y = cosPhi1 * sinPhi - sinPhi1 * cosPhi * cosLambda;
+            var cosC = sinPhi1 * sinPhi + cosPhi1 * cosPhi * cosLambda; // (5-3)
+            cosC = Math.Min(Math.Max(cosC, -1d), 1d); // protect against rounding errors
+            var k = 2d / (1d + cosC); // p.157 (21-4), k0 == 1
+
+            return new Point(
+                EquatorialRadius * k * x,
+                EquatorialRadius * k * y); // p.157 (21-2/3)
+        }
+
+        public override Location MapToLocation(double x, double y)
+        {
+            var rho = Math.Sqrt(x * x + y * y);
+            var c = 2d * Math.Atan(rho / (2d * EquatorialRadius)); // p.159 (21-15), k0 == 1
+            var cosC = Math.Cos(c);
+            var sinC = Math.Sin(c);
+
+            var phi1 = LatitudeOfOrigin * Math.PI / 180d;
+            var cosPhi1 = Math.Cos(phi1);
+            var sinPhi1 = Math.Sin(phi1);
+            var phi = Math.Asin(cosC * sinPhi1 + y * sinC * cosPhi1 / rho); // (20-14)
+            double u, v;
+
+            if (LatitudeOfOrigin == 90d) // (20-16)
+            {
+                u = x;
+                v = -y;
+            }
+            else if (LatitudeOfOrigin == -90d) // (20-17)
+            {
+                u = x;
+                v = y;
+            }
+            else // (20-15)
+            {
+                u = x * sinC;
+                v = rho * cosPhi1 * cosC - y * sinPhi1 * sinC;
+            }
+
+            return new Location(
+                phi * 180d / Math.PI,
+                Math.Atan2(u, v) * 180d / Math.PI + CentralMeridian);
+        }
+    }
+}