From 0dbdd4c81091b662de45ff4942c6bbb16a2484ca Mon Sep 17 00:00:00 2001
From: ClemensF <fischer.clemens@gmail.com>
Date: Mon, 16 Dec 2019 18:35:04 +0100
Subject: [PATCH] Version 4.16.0. Improved MapProjection.

---
 .../Shared/AzimuthalEquidistantProjection.cs  |  2 +-
 MapControl/Shared/AzimuthalProjection.cs      | 31 ++++++++++++-------
 MapControl/Shared/GnomonicProjection.cs       |  2 +-
 MapControl/Shared/OrthographicProjection.cs   |  2 +-
 MapControl/Shared/StereographicProjection.cs  |  2 +-
 5 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/MapControl/Shared/AzimuthalEquidistantProjection.cs b/MapControl/Shared/AzimuthalEquidistantProjection.cs
index 3630cecf..aacbcfa1 100644
--- a/MapControl/Shared/AzimuthalEquidistantProjection.cs
+++ b/MapControl/Shared/AzimuthalEquidistantProjection.cs
@@ -36,7 +36,7 @@ namespace MapControl
         {
             if (point.X == 0d && point.Y == 0d)
             {
-                return ProjectionCenter;
+                return new Location(ProjectionCenter.Latitude, ProjectionCenter.Longitude);
             }
 
             var azimuth = Math.Atan2(point.X, point.Y);
diff --git a/MapControl/Shared/AzimuthalProjection.cs b/MapControl/Shared/AzimuthalProjection.cs
index 79728336..79f51956 100644
--- a/MapControl/Shared/AzimuthalProjection.cs
+++ b/MapControl/Shared/AzimuthalProjection.cs
@@ -71,18 +71,27 @@ namespace MapControl
         /// </summary>
         public static Location GetLocation(Location location, double azimuth, double distance)
         {
-            var lat1 = location.Latitude * Math.PI / 180d;
-            var sinDistance = Math.Sin(distance);
-            var cosDistance = Math.Cos(distance);
-            var cosAzimuth = Math.Cos(azimuth);
-            var sinAzimuth = Math.Sin(azimuth);
-            var cosLat1 = Math.Cos(lat1);
-            var sinLat1 = Math.Sin(lat1);
-            var sinLat2 = sinLat1 * cosDistance + cosLat1 * sinDistance * cosAzimuth;
-            var lat2 = Math.Asin(Math.Min(Math.Max(sinLat2, -1d), 1d));
-            var dLon = Math.Atan2(sinDistance * sinAzimuth, cosLat1 * cosDistance - sinLat1 * sinDistance * cosAzimuth);
+            var lat = location.Latitude;
+            var lon = location.Longitude;
 
-            return new Location(lat2 * 180d / Math.PI, location.Longitude + dLon * 180d / Math.PI);
+            if (distance > 0d)
+            {
+                var lat1 = lat * Math.PI / 180d;
+                var sinDistance = Math.Sin(distance);
+                var cosDistance = Math.Cos(distance);
+                var cosAzimuth = Math.Cos(azimuth);
+                var sinAzimuth = Math.Sin(azimuth);
+                var cosLat1 = Math.Cos(lat1);
+                var sinLat1 = Math.Sin(lat1);
+                var sinLat2 = sinLat1 * cosDistance + cosLat1 * sinDistance * cosAzimuth;
+                var lat2 = Math.Asin(Math.Min(Math.Max(sinLat2, -1d), 1d));
+                var dLon = Math.Atan2(sinDistance * sinAzimuth, cosLat1 * cosDistance - sinLat1 * sinDistance * cosAzimuth);
+
+                lat = lat2 * 180d / Math.PI;
+                lon += dLon * 180d / Math.PI;
+            }
+
+            return new Location(lat, lon);
         }
     }
 }
diff --git a/MapControl/Shared/GnomonicProjection.cs b/MapControl/Shared/GnomonicProjection.cs
index 26ea93cf..f1f07f9e 100644
--- a/MapControl/Shared/GnomonicProjection.cs
+++ b/MapControl/Shared/GnomonicProjection.cs
@@ -41,7 +41,7 @@ namespace MapControl
         {
             if (point.X == 0d && point.Y == 0d)
             {
-                return ProjectionCenter;
+                return new Location(ProjectionCenter.Latitude, ProjectionCenter.Longitude);
             }
 
             var azimuth = Math.Atan2(point.X, point.Y);
diff --git a/MapControl/Shared/OrthographicProjection.cs b/MapControl/Shared/OrthographicProjection.cs
index acea7799..08855756 100644
--- a/MapControl/Shared/OrthographicProjection.cs
+++ b/MapControl/Shared/OrthographicProjection.cs
@@ -40,7 +40,7 @@ namespace MapControl
         {
             if (point.X == 0d && point.Y == 0d)
             {
-                return ProjectionCenter;
+                return new Location(ProjectionCenter.Latitude, ProjectionCenter.Longitude);
             }
 
             var s = TrueScale * 180d / Math.PI;
diff --git a/MapControl/Shared/StereographicProjection.cs b/MapControl/Shared/StereographicProjection.cs
index cd9c7171..ef9fa244 100644
--- a/MapControl/Shared/StereographicProjection.cs
+++ b/MapControl/Shared/StereographicProjection.cs
@@ -39,7 +39,7 @@ namespace MapControl
         {
             if (point.X == 0d && point.Y == 0d)
             {
-                return ProjectionCenter;
+                return new Location(ProjectionCenter.Latitude, ProjectionCenter.Longitude);
             }
 
             var azimuth = Math.Atan2(point.X, point.Y);