Once downloaded that image must be rendered into a PNG. Skye's Building Zurich (which I strongly recommend viewing) uses a precision that yields 512 map segments. The program can be purchased for about $35 for those wanting more precision. The image for an 18 Sq Km section comes in 30 segments which can be stiched together via the Map Combiner tool that is part of the program.
The Google Maps Downloader will download images at a zoom of 13 for free which is precise enough for most users.
