I need to show a set of points on a basemap, e.g., ESRI's streets map. I use esri.graphicsExtent(graphics) to set the default extent. The problem here is that on some regions, the basemap is not available for a given extent. Altough the user can zoom out to see the points, it would be nice if I can set the default extent in a better way. The question is: for a given extent, is there a way to check whether the basemap is available?