private static void LoadEsriImagery(LayerHelper layerHelper)
        {
            var tileSource = new ArcGisTileSource("http://services.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer", EsriWorldSchema.GetSchema());
            var esri = new BaseTileLayer(tileSource)
            {
                LayerName = "World Imagery",
                TumbnailPath = "Resources/Images/world_imagery.png",
                CopyrightImage = "Resources/Images/esriLogo.png",
                Enabled = true
            };

            layerHelper.AddBaseLayer(esri);
        }