diff --git a/MapProjections/Shared/GeoApiProjection.cs b/MapProjections/Shared/GeoApiProjection.cs
index d59ae7b0..0dc1f039 100644
--- a/MapProjections/Shared/GeoApiProjection.cs
+++ b/MapProjections/Shared/GeoApiProjection.cs
@@ -30,12 +30,13 @@ namespace MapControl.Projections
         private double scaleFactor;
         private string bboxFormat;
 
-        public GeoApiProjection(string wkt = null)
+        protected GeoApiProjection()
         {
-            if (wkt != null)
-            {
-                WKT = wkt;
-            }
+        }
+
+        public GeoApiProjection(string wkt)
+        {
+            WKT = wkt;
         }
 
         /// <summary>
@@ -46,7 +47,7 @@ namespace MapControl.Projections
         public string WKT
         {
             get { return CoordinateSystem?.WKT; }
-            set { CoordinateSystem = new CoordinateSystemFactory().CreateFromWkt(value); }
+            protected set { CoordinateSystem = new CoordinateSystemFactory().CreateFromWkt(value); }
         }
 
         /// <summary>
@@ -55,7 +56,7 @@ namespace MapControl.Projections
         public ICoordinateSystem CoordinateSystem
         {
             get { return coordinateSystem; }
-            set
+            protected set
             {
                 coordinateSystem = value ?? throw new ArgumentNullException(nameof(value));
 
diff --git a/MapProjections/Shared/UtmProjection.cs b/MapProjections/Shared/UtmProjection.cs
index c5c9dcf9..d7aaa9a9 100644
--- a/MapProjections/Shared/UtmProjection.cs
+++ b/MapProjections/Shared/UtmProjection.cs
@@ -9,10 +9,6 @@ namespace MapControl.Projections
 {
     public class UtmProjection : GeoApiProjection
     {
-        public UtmProjection()
-        {
-        }
-
         public UtmProjection(int zone, bool north)
         {
             SetZone(zone, north);
@@ -20,17 +16,12 @@ namespace MapControl.Projections
 
         public UtmProjection(Location location)
         {
-            SetZone(location);
+            var zone = Math.Min((int)Math.Floor(Location.NormalizeLongitude(location.Longitude) + 180d) / 6 + 1, 60);
+
+            SetZone(zone, location.Latitude >= 0d);
         }
 
-        public void SetZone(Location location)
-        {
-            var zoneNumber = Math.Min((int)(Location.NormalizeLongitude(location.Longitude) + 180d) / 6 + 1, 60);
-
-            SetZone(zoneNumber, location.Latitude >= 0d);
-        }
-
-        public void SetZone(int zone, bool north)
+        protected void SetZone(int zone, bool north)
         {
             if (zone < 1 || zone > 60)
             {
diff --git a/SampleApps/ProjectionDemo/MainWindow.xaml.cs b/SampleApps/ProjectionDemo/MainWindow.xaml.cs
index 3a928aed..ead69692 100644
--- a/SampleApps/ProjectionDemo/MainWindow.xaml.cs
+++ b/SampleApps/ProjectionDemo/MainWindow.xaml.cs
@@ -25,10 +25,7 @@ namespace ProjectionDemo
         {
             viewModel.Projections.Add(new MapControl.Projections.WebMercatorProjection());
 
-            viewModel.Projections.Add(new GeoApiProjection
-            {
-                WKT = await httpClient.GetStringAsync("https://epsg.io/25832.wkt") // ETRS89 / UTM zone 32N
-            });
+            viewModel.Projections.Add(new GeoApiProjection(await httpClient.GetStringAsync("https://epsg.io/25832.wkt"))); // ETRS89 / UTM zone 32N
 
             viewModel.Layers.Add(
                 "OpenStreetMap WMS",