Virtual Earth Web Services with Mobile and Desktop Images

As I’ve always had an interest in building mobile applications it interested me to see that the Virtual Earth Web Services have support for the generation of images that are optimised for mobile devices.  Curious as to what this meant I took some time to look at the differences between using the Desktop and Mobile values for the DeviceType property when requesting map images from the Imagery service.

image image

Both images here are of Perth, Western Australia (-31.953619,115.858555); both are 200 x 200; both at a zoom level of 12 and both with the MapStyle set to Road.  The difference is that the one of the right was generated using the Desktop value, the one on the right with the Mobile value. Saving these images to the filesystem reveals a significant difference in file/download size.  The desktop image is approximately 88K, where as the mobile image is only around 14.5K.

Interestingly, when you set the MapStyle to Aerial, there is no visible difference in the image, and further when you look at the file size they are exactly the same size.  I’m sure this is probably documented somewhere that the DeviceType doesn’t apply to Aerial images….