Bing Base Map - Map MinimumResolution Not Set? (Can Zoom In Beyond Lowest Bing Level)

DavidMarley

The Esri Silverlight API documentation states (here among other places) that when tiled base map services are used, the map's MinimumResolution and MaximumResolution properties are set automatically.  But this does not seem to be the case for Bing Maps tiled layer.  So for example, using the Esri World Street map (http://services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer) as a base map layer, the Map control's MinimumResolution is set properly and I cannot zoom in beyond the lowest tile level of the service.  However if the Bing tiled service is used, the MinimumResolution appears not to be set (or set correctly) and I am able to zoom in beyond the lowest Bing level.  Does anyone know why this is? 

You can see this behavior for yourself right in the Esri Online samples (see "Mapping > ArcGIS Tiled Layer" and "Bing Maps > Imagery" samples).

Through some debugging, I can see that when using the Esri service the MinimumResolution is set to 0.298582141647617 which you can see from the service's documentation (here) is the correct value and this works fine.  When using the Bing layer, the map's MinimumResolution is 0.0373227677173711.  The lowest Bing level displays down to around 0.225, and if you zoom in beyond that you get the "no data" images.

This is easily fixed by explicitely setting the map's MinimumResolution when using the Bing layer, for example from code-behind:

// hard code min resolution so user can't zoom in past lowest Bing level MainMap.MinimumResolution = 0.225;

But why is this not set for Bing layers as the documentation says it should be?

DominiqueBroux

By default the minimum resolution is set to the minimum resolution that might theorically be supported by the bing layers.

But in practice the minimum resolution is depending on the area you are zooming in.

For example, you wont get the same result if you zoom in over the ocean or if you zoom in over New York.

The workaround might be you to set the layer minimum resolution depending on the area you are covering.