Improved MapProjections

MapControl/Shared/MapProjection.cs

@@ -5,7 +5,6 @@
 using System;
 #if WINDOWS_UWP
 using Windows.Foundation;
-using Windows.UI.Xaml.Media;
 #else
 using System.Windows;
 using System.Windows.Media;
@@ -134,9 +133,17 @@ namespace MapControl
         /// </summary>
         public BoundingBox ViewportRectToBoundingBox(Rect rect)
         {
-            var transform = new MatrixTransform { Matrix = InverseViewportTransform };
+            var p1 = InverseViewportTransform.Transform(new Point(rect.X, rect.Y));
+            var p2 = InverseViewportTransform.Transform(new Point(rect.X, rect.Y + rect.Height));
+            var p3 = InverseViewportTransform.Transform(new Point(rect.X + rect.Width, rect.Y));
+            var p4 = InverseViewportTransform.Transform(new Point(rect.X + rect.Width, rect.Y + rect.Height));
 
-            return RectToBoundingBox(transform.TransformBounds(rect));
+            rect.X = Math.Min(p1.X, Math.Min(p2.X, Math.Min(p3.X, p4.X)));
+            rect.Y = Math.Min(p1.Y, Math.Min(p2.Y, Math.Min(p3.Y, p4.Y)));
+            rect.Width = Math.Max(p1.X, Math.Max(p2.X, Math.Max(p3.X, p4.X))) - rect.X;
+            rect.Height = Math.Max(p1.Y, Math.Max(p2.Y, Math.Max(p3.Y, p4.Y))) - rect.Y;
+
+            return RectToBoundingBox(rect);
         }
 
         /// <summary>

MapControl/UWP/Matrix.UWP.cs

@@ -6,6 +6,9 @@ using System;
 
 namespace MapControl
 {
+    /// <summary>
+    /// Replaces Windows.UI.Xaml.Media.Matrix to achieve necessary floating point precision.
+    /// </summary>
     public struct Matrix
     {
         public double M11 { get; set; }

MapControl/UWP/Point.UWP.cs

@@ -4,6 +4,9 @@
 
 namespace MapControl
 {
+    /// <summary>
+    /// Replaces Windows.Foundation.Point to achieve necessary floating point precision.
+    /// </summary>
     public struct Point
     {
         public double X { get; set; }

MapProjections/Shared/GeoApiProjection.cs

@@ -19,15 +19,15 @@ namespace MapControl.Projections
     /// </summary>
     public class GeoApiProjection : MapProjection
     {
-        private IProjectedCoordinateSystem coordinateSystem;
+        private ICoordinateSystem coordinateSystem;
 
-        public IMathTransform MathTransform { get; private set; }
+        public IMathTransform LocationToPointTransform { get; private set; }
-        public IMathTransform InverseTransform { get; private set; }
+        public IMathTransform PointToLocationTransform { get; private set; }
 
         /// <summary>
         /// Gets or sets the IProjectedCoordinateSystem of the MapProjection.
         /// </summary>
-        public IProjectedCoordinateSystem CoordinateSystem
+        public ICoordinateSystem CoordinateSystem
         {
             get { return coordinateSystem; }
             set
@@ -39,43 +39,45 @@ namespace MapControl.Projections
 
                 coordinateSystem = value;
 
-                var coordinateTransform = new CoordinateTransformationFactory()
+                var transformFactory = new CoordinateTransformationFactory();
-                    .CreateFromCoordinateSystems(GeographicCoordinateSystem.WGS84, coordinateSystem);
 
-                MathTransform = coordinateTransform.MathTransform;
+                LocationToPointTransform = transformFactory
-                InverseTransform = MathTransform.Inverse();
+                    .CreateFromCoordinateSystems(GeographicCoordinateSystem.WGS84, coordinateSystem)
+                    .MathTransform;
+
+                PointToLocationTransform = transformFactory
+                    .CreateFromCoordinateSystems(coordinateSystem, GeographicCoordinateSystem.WGS84)
+                    .MathTransform;
 
                 CrsId = (!string.IsNullOrEmpty(coordinateSystem.Authority) && coordinateSystem.AuthorityCode > 0)
                     ? string.Format("{0}:{1}", coordinateSystem.Authority, coordinateSystem.AuthorityCode)
                     : null;
 
-                if (!IsWebMercator)
+                IsWebMercator = CrsId == "EPSG:3857" || CrsId == "EPSG:900913";
-                {
-                    IsWebMercator = CrsId == "EPSG:3857" || CrsId == "EPSG:900913";
-                }
 
-                var projection = coordinateSystem.Projection;
+                var projectedCoordinateSystem = coordinateSystem as IProjectedCoordinateSystem;
-                var scaleFactor = projection.GetParameter("scale_factor");
 
-                if (scaleFactor != null)
+                if (projectedCoordinateSystem != null)
-                {
-                    TrueScale = scaleFactor.Value * Wgs84MetersPerDegree;
-                }
-
-                if (!IsNormalCylindrical)
                 {
+                    var projection = projectedCoordinateSystem.Projection;
                     var centralMeridian = projection.GetParameter("central_meridian") ?? projection.GetParameter("longitude_of_origin");
                     var centralParallel = projection.GetParameter("latitude_of_origin") ?? projection.GetParameter("central_parallel");
                     var falseEasting = projection.GetParameter("false_easting");
                     var falseNorthing = projection.GetParameter("false_northing");
+                    var scaleFactor = projection.GetParameter("scale_factor");
 
-                    if (centralMeridian != null && centralMeridian.Value == 0d &&
+                    IsNormalCylindrical =
+                        centralMeridian != null && centralMeridian.Value == 0d &&
                         centralParallel != null && centralParallel.Value == 0d &&
                         (falseEasting == null || falseEasting.Value == 0d) &&
-                        (falseNorthing == null || falseNorthing.Value == 0d))
+                        (falseNorthing == null || falseNorthing.Value == 0d);
-                    {
+
-                        IsNormalCylindrical = true;
+                    TrueScale = (scaleFactor != null ? scaleFactor.Value : 1d) * Wgs84MetersPerDegree;
-                    }
+                }
+                else
+                {
+                    IsNormalCylindrical = true;
+                    TrueScale = 1d;
                 }
             }
         }
@@ -88,29 +90,29 @@ namespace MapControl.Projections
         public string WKT
         {
             get { return CoordinateSystem?.WKT; }
-            set { CoordinateSystem = (IProjectedCoordinateSystem)new CoordinateSystemFactory().CreateFromWkt(value); }
+            set { CoordinateSystem = new CoordinateSystemFactory().CreateFromWkt(value); }
         }
 
         public override Point LocationToPoint(Location location)
         {
-            if (MathTransform == null)
+            if (LocationToPointTransform == null)
             {
                 throw new InvalidOperationException("The CoordinateSystem property is not set.");
             }
 
-            var coordinate = MathTransform.Transform(new Coordinate(location.Longitude, location.Latitude));
+            var coordinate = LocationToPointTransform.Transform(new Coordinate(location.Longitude, location.Latitude));
 
             return new Point(coordinate.X, coordinate.Y);
         }
 
         public override Location PointToLocation(Point point)
         {
-            if (InverseTransform == null)
+            if (PointToLocationTransform == null)
             {
                 throw new InvalidOperationException("The CoordinateSystem property is not set.");
             }
 
-            var coordinate = InverseTransform.Transform(new Coordinate(point.X, point.Y));
+            var coordinate = PointToLocationTransform.Transform(new Coordinate(point.X, point.Y));
 
             return new Location(coordinate.Y, coordinate.X);
         }

MapProjections/Shared/WebMercatorProjection.cs

@@ -18,8 +18,6 @@ namespace MapControl.Projections
     {
         public WebMercatorProjection()
         {
-            IsWebMercator = true;
-            IsNormalCylindrical = true;
             CoordinateSystem = ProjectedCoordinateSystem.WebMercator;
         }
 

MapProjections/Shared/WorldMercatorProjection.cs

@@ -17,23 +17,24 @@ namespace MapControl.Projections
     {
         public WorldMercatorProjection()
         {
-            IsNormalCylindrical = true;
+            WKT = "PROJCS[\"WGS 84 / World Mercator\"," +
-            WKT = "PROJCS[\"WGS 84 / World Mercator\","
+                "GEOGCS[\"WGS 84\"," +
-                + "GEOGCS[\"WGS 84\","
+                    "DATUM[\"WGS_1984\"," +
-                + "DATUM[\"WGS_1984\", SPHEROID[\"WGS 84\", 6378137, 298.257223563, AUTHORITY[\"EPSG\", \"7030\"]], AUTHORITY[\"EPSG\", \"6326\"]],"
+                        "SPHEROID[\"WGS 84\",6378137,298.257223563,AUTHORITY[\"EPSG\",\"7030\"]]," +
-                + "PRIMEM[\"Greenwich\", 0, AUTHORITY[\"EPSG\", \"8901\"]],"
+                        "AUTHORITY[\"EPSG\",\"6326\"]]," +
-                + "UNIT[\"degree\", 0.0174532925199433, AUTHORITY[\"EPSG\", \"9122\"]],"
+                    "PRIMEM[\"Greenwich\",0,AUTHORITY[\"EPSG\",\"8901\"]]," +
-                + "AUTHORITY[\"EPSG\", \"4326\"]],"
+                    "UNIT[\"degree\",0.0174532925199433,AUTHORITY[\"EPSG\",\"9122\"]]," +
-                + "PROJECTION[\"Mercator_1SP\"],"
+                    "AUTHORITY[\"EPSG\",\"4326\"]]," +
-                + "PARAMETER[\"latitude_of_origin\", 0],"
+                "PROJECTION[\"Mercator_1SP\"]," +
-                + "PARAMETER[\"central_meridian\", 0],"
+                "PARAMETER[\"latitude_of_origin\",0]," +
-                + "PARAMETER[\"scale_factor\", 1],"
+                "PARAMETER[\"central_meridian\",0]," +
-                + "PARAMETER[\"false_easting\", 0],"
+                "PARAMETER[\"scale_factor\",1]," +
-                + "PARAMETER[\"false_northing\", 0],"
+                "PARAMETER[\"false_easting\",0]," +
-                + "UNIT[\"metre\", 1, AUTHORITY[\"EPSG\", \"9001\"]],"
+                "PARAMETER[\"false_northing\",0]," +
-                + "AXIS[\"Easting\", EAST],"
+                "UNIT[\"metre\",1,AUTHORITY[\"EPSG\",\"9001\"]]," +
-                + "AXIS[\"Northing\", NORTH],"
+                "AXIS[\"Easting\",EAST]," +
-                + "AUTHORITY[\"EPSG\", \"3395\"]]";
+                "AXIS[\"Northing\",NORTH]," +
+                "AUTHORITY[\"EPSG\",\"3395\"]]";
         }
 
         public override Vector GetMapScale(Location location)