Add GeographyUtils class and Distance.BetweenPoints method

Xamarin.Forms.Controls/GalleryPages/MapElementsGallery.xaml.cs

@@ -92,39 +92,12 @@ void MapClicked(object sender, MapClickedEventArgs e)
 					}
 					else
 					{
-						_circle.Radius = CalculateDistance(_circle.Center, e.Position);
+						_circle.Radius = Distance.BetweenPositions(_circle.Center, e.Position);
 					}
 					break;
 			}
 		}
 
-		Distance CalculateDistance(Position position1, Position position2)
-		{
-			const double EarthRadiusKm = 6371;
-
-			var latitude1 = DegreeToRadian(position1.Latitude);
-			var longitude1 = DegreeToRadian(position1.Longitude);
-
-			var latitude2 = DegreeToRadian(position2.Latitude);
-			var longitude2 = DegreeToRadian(position2.Longitude);
-
-			var distance = Math.Sin((latitude2 - latitude1) / 2.0);
-			distance *= distance;
-
-			var intermediate = Math.Sin((longitude2 - longitude1) / 2.0);
-			intermediate *= intermediate;
-
-			distance = distance + Math.Cos(latitude1) * Math.Cos(latitude2) * intermediate;
-			distance = 2 * EarthRadiusKm * Math.Atan2(Math.Sqrt(distance), Math.Sqrt(1 - distance));
-
-			return Distance.FromKilometers(distance);
-		}
-
-		double DegreeToRadian(double degree)
-		{
-			return degree * Math.PI / 180.0;
-		}
-
 		void PickerSelectionChanged(object sender, EventArgs e)
 		{
 			Enum.TryParse((string)ElementPicker.SelectedItem, out _selectedType);

Xamarin.Forms.Maps.UWP/MapRenderer.cs

@@ -248,7 +248,7 @@ protected Geopath PositionsToGeopath(IList<Position> positions)
 			{
 				return new Geopath(new[]
 				{
-					new BasicGeoposition(), 
+					new BasicGeoposition(),
 				});
 			}
 		}
@@ -347,38 +347,26 @@ protected virtual MapPolygon LoadCircle(Circle circle)
 
 		Geopath GenerateCirclePath(Circle circle)
 		{
-			const double EarthRadiusKm = 6371;
-
 			var positions = new List<Position>();
-			double latitude = DegreesToRadians(circle.Center.Latitude);
-			double longitude = DegreesToRadians(circle.Center.Longitude);
-			double distance = circle.Radius.Kilometers / EarthRadiusKm;
+			double centerLatitude = circle.Center.Latitude.ToRadians();
+			double centerLongitude = circle.Center.Longitude.ToRadians();
+			double distance = circle.Radius.Kilometers / GeographyUtils.EarthRadiusKm;
 
 			for (int angle = 0; angle <= 360; angle++)
 			{
-				double angleInRadians = DegreesToRadians(angle);
-				double latitudeInRadians = Math.Asin(Math.Sin(latitude) * Math.Cos(distance) +
-				                                     Math.Cos(latitude) * Math.Sin(distance) * Math.Cos(angleInRadians));
-				double longitudeInRadians =
-					longitude + Math.Atan2(Math.Sin(angleInRadians) * Math.Sin(distance) * Math.Cos(latitude),
-						Math.Cos(distance) - Math.Sin(latitude) * Math.Sin(latitudeInRadians));
+				double angleInRadians = ((double)angle).ToRadians();
+				double latitude = Math.Asin(Math.Sin(centerLatitude) * Math.Cos(distance) +
+				                            Math.Cos(centerLatitude) * Math.Sin(distance) * Math.Cos(angleInRadians));
+				double longitude = centerLongitude +
+				                   Math.Atan2(Math.Sin(angleInRadians) * Math.Sin(distance) * Math.Cos(centerLatitude),
+					                   Math.Cos(distance) - Math.Sin(centerLatitude) * Math.Sin(latitude));
 
-				positions.Add(new Position(RadiansToDegrees(latitudeInRadians), RadiansToDegrees(longitudeInRadians)));
+				positions.Add(new Position(latitude.ToDegrees(), longitude.ToDegrees()));
 			}
 
 			return PositionsToGeopath(positions);
 		}
 
-		double DegreesToRadians(double degrees)
-		{
-			return degrees * Math.PI / 180.0;
-		}
-
-		double RadiansToDegrees(double radians)
-		{
-			return radians / Math.PI * 180.0;
-		}
-
 		void OnCirclePropertyChanged(Circle circle, PropertyChangedEventArgs e)
 		{
 			var mapPolygon = (MapPolygon)circle.MapElementId;
@@ -401,7 +389,7 @@ void OnCirclePropertyChanged(Circle circle, PropertyChangedEventArgs e)
 				mapPolygon.FillColor = circle.FillColor.ToWindowsColor();
 			}
 			else if (e.PropertyName == Circle.CenterProperty.PropertyName ||
-			         e.PropertyName == Circle.RadiusProperty.PropertyName)
+					 e.PropertyName == Circle.RadiusProperty.PropertyName)
 			{
 				mapPolygon.Path = GenerateCirclePath(circle);
 			}

Xamarin.Forms.Maps/Distance.cs

@@ -1,4 +1,5 @@
-using System.Diagnostics;
+using System;
+using System.Diagnostics;
 
 namespace Xamarin.Forms.Maps
 {
@@ -48,6 +49,26 @@ public static Distance FromKilometers(double kilometers)
 			return new Distance(kilometers * MetersPerKilometer);
 		}
 
+		public static Distance BetweenPositions(Position position1, Position position2)
+		{
+			var latitude1 = position1.Latitude.ToRadians();
+			var longitude1 = position1.Longitude.ToRadians();
+
+			var latitude2 = position2.Latitude.ToRadians();
+			var longitude2 = position2.Longitude.ToRadians();
+
+			var distance = Math.Sin((latitude2 - latitude1) / 2.0);
+			distance *= distance;
+
+			var intermediate = Math.Sin((longitude2 - longitude1) / 2.0);
+			intermediate *= intermediate;
+
+			distance = distance + Math.Cos(latitude1) * Math.Cos(latitude2) * intermediate;
+			distance = 2 * GeographyUtils.EarthRadiusKm * Math.Atan2(Math.Sqrt(distance), Math.Sqrt(1 - distance));
+
+			return FromKilometers(distance);
+		}
+
 		public bool Equals(Distance other)
 		{
 			return Meters.Equals(other.Meters);

Xamarin.Forms.Maps/GeographyUtils.cs

@@ -0,0 +1,19 @@
+using System;
+
+namespace Xamarin.Forms.Maps
+{
+	public static class GeographyUtils
+	{
+		public const double EarthRadiusKm = 6371;
+
+		public static double ToRadians(this double degrees)
+		{
+			return degrees * Math.PI / 180.0;
+		}
+
+		public static double ToDegrees(this double radians)
+		{
+			return radians / Math.PI * 180.0;
+		}
+	}
+}

Xamarin.Forms.Maps/MapSpan.cs

@@ -4,8 +4,7 @@ namespace Xamarin.Forms.Maps
 {
 	public sealed class MapSpan
 	{
-		const double EarthRadiusKm = 6371;
-		const double EarthCircumferenceKm = EarthRadiusKm * 2 * Math.PI;
+		const double EarthCircumferenceKm = GeographyUtils.EarthRadiusKm * 2 * Math.PI;
 		const double MinimumRangeDegrees = 0.001 / EarthCircumferenceKm * 360; // 1 meter
 
 		public MapSpan(Position center, double latitudeDegrees, double longitudeDegrees)