Version 4: Upgrade to VS 2017

MapControl/Shared/StereographicProjection.cs

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+// XAML Map Control - https://github.com/ClemensFischer/XAML-Map-Control
+// © 2017 Clemens Fischer
+// Licensed under the Microsoft Public License (Ms-PL)
+
+using System;
+#if WINDOWS_UWP
+using Windows.Foundation;
+#else
+using System.Windows;
+#endif
+
+namespace MapControl
+{
+    /// <summary>
+    /// Transforms map coordinates according to the Gnomonic Projection.
+    /// </summary>
+    public class StereographicProjection : AzimuthalProjection
+    {
+        public StereographicProjection()
+            : this("AUTO2:97002") // GeoServer non-standard CRS ID
+        {
+        }
+
+        public StereographicProjection(string crsId)
+        {
+            CrsId = crsId;
+        }
+
+        public override Point LocationToPoint(Location location)
+        {
+            if (location.Equals(projectionCenter))
+            {
+                return new Point();
+            }
+
+            double azimuth, distance;
+
+            GetAzimuthDistance(projectionCenter, location, out azimuth, out distance);
+
+            var mapDistance = 2d * Wgs84EquatorialRadius * Math.Tan(distance / 2d);
+
+            return new Point(mapDistance * Math.Sin(azimuth), mapDistance * Math.Cos(azimuth));
+        }
+
+        public override Location PointToLocation(Point point)
+        {
+            if (point.X == 0d && point.Y == 0d)
+            {
+                return projectionCenter;
+            }
+
+            var azimuth = Math.Atan2(point.X, point.Y);
+            var mapDistance = Math.Sqrt(point.X * point.X + point.Y * point.Y);
+            var distance = 2d * Math.Atan(mapDistance / (2d * Wgs84EquatorialRadius));
+
+            return GetLocation(projectionCenter, azimuth, distance);
+        }
+    }
+}