diff --git a/MapControl/Shared/BoundingBoxTileSource.cs b/MapControl/Shared/BoundingBoxTileSource.cs
index 7b6b5e2a..8157f7b4 100644
--- a/MapControl/Shared/BoundingBoxTileSource.cs
+++ b/MapControl/Shared/BoundingBoxTileSource.cs
@@ -4,39 +4,61 @@
 
 using System;
 using System.Globalization;
+using System.Threading.Tasks;
+using System.Windows.Media;
 
 namespace MapControl
 {
     public class BoundingBoxTileSource : TileSource
     {
         public override Uri GetUri(int column, int row, int zoomLevel)
+        {
+            GetBounds(column, row, zoomLevel, out double west, out double south, out double east, out double north);
+
+            return GetUri(west, south, east, north);
+        }
+
+        public override Task<ImageSource> LoadImageAsync(int column, int row, int zoomLevel)
+        {
+            GetBounds(column, row, zoomLevel, out double west, out double south, out double east, out double north);
+
+            return LoadImageAsync(west, south, east, north);
+        }
+
+        protected virtual Uri GetUri(double west, double south, double east, double north)
         {
             Uri uri = null;
 
             if (UriTemplate != null)
             {
-                var tileSize = 360d / (1 << zoomLevel); // tile size in degrees
-                var west = MapProjection.Wgs84MeterPerDegree * (column * tileSize - 180d);
-                var east = MapProjection.Wgs84MeterPerDegree * ((column + 1) * tileSize - 180d);
-                var south = MapProjection.Wgs84MeterPerDegree * (180d - (row + 1) * tileSize);
-                var north = MapProjection.Wgs84MeterPerDegree * (180d - row * tileSize);
+                var w = west.ToString("F2", CultureInfo.InvariantCulture);
+                var e = east.ToString("F2", CultureInfo.InvariantCulture);
+                var s = south.ToString("F2", CultureInfo.InvariantCulture);
+                var n = north.ToString("F2", CultureInfo.InvariantCulture);
 
-                if (UriTemplate.Contains("{bbox}"))
-                {
-                    uri = new Uri(UriTemplate.Replace("{bbox}",
-                        string.Format(CultureInfo.InvariantCulture, "{0:F2},{1:F2},{2:F2},{3:F2}", west, south, east, north)));
-                }
-                else
-                {
-                    uri = new Uri(UriTemplate
-                        .Replace("{west}", west.ToString("F2", CultureInfo.InvariantCulture))
-                        .Replace("{south}", south.ToString("F2", CultureInfo.InvariantCulture))
-                        .Replace("{east}", east.ToString("F2", CultureInfo.InvariantCulture))
-                        .Replace("{north}", north.ToString("F2", CultureInfo.InvariantCulture)));
-                }
+                uri = UriTemplate.Contains("{bbox}")
+                    ? new Uri(UriTemplate.Replace("{bbox}", $"{w},{s},{e},{n}"))
+                    : new Uri(UriTemplate.Replace("{west}", w).Replace("{south}", s).Replace("{east}", e).Replace("{north}", n));
             }
 
             return uri;
         }
+
+        protected virtual Task<ImageSource> LoadImageAsync(double west, double south, double east, double north)
+        {
+            var uri = GetUri(west, south, east, north);
+
+            return uri != null ? ImageLoader.LoadImageAsync(uri) : Task.FromResult((ImageSource)null);
+        }
+
+        protected void GetBounds(int column, int row, int zoomLevel, out double west, out double south, out double east, out double north)
+        {
+            var tileSize = 360d / (1 << zoomLevel); // tile size in degrees
+
+            west = MapProjection.Wgs84MeterPerDegree * (column * tileSize - 180d);
+            east = MapProjection.Wgs84MeterPerDegree * ((column + 1) * tileSize - 180d);
+            south = MapProjection.Wgs84MeterPerDegree * (180d - (row + 1) * tileSize);
+            north = MapProjection.Wgs84MeterPerDegree * (180d - row * tileSize);
+        }
     }
 }