Android scaling overlay on mapview on zoom ratios etc

Does anyone know the scale ratio for android mapview zoom values?

开发者_开发百科For example if I wanted to overlay an image that was say 1 degree GPS map space square.. what size in pixels should that be when the zoom is at maximimum? Then what would I need to scale the image by per zoom level?

Is this published or known anywhere?

To do this you need to use the getProjection method in the MapView clas http://code.google.com/android/add-ons/google-apis/reference/com/google/android/maps/MapView.html#getProjection()

but I don't believe you can scale overlays using the default methods, you may need to override or expand the drawAt method for the Overlay class.