I covered this in the GPS section of my ZS20 / TZ30 review! Here's an excerpt:
"...it's not surprising to find the maps are not built into the camera's internal memory. Instead they're loaded as separate regions via a supplied DVD and utility onto spare space on your memory card. The complete global installation will consume 6.37GB, but you can choose to only load the regions you want, and you can remove or supplement them later.
The separate regions and their map sizes are: Japan (731MB), South and Southeast Asia (317MB), Oceania (259MB), North and Central America (1.88GB), South America (237MB), Northern Europe (2.62GB), Eastern Europe (1.29GB), Western Europe (2.47GB), West Asia and Africa (277MB) and Russia and North Asia (1.51GB).
Storing the maps on the card is necessary due to their size, but it does make them dependant on the actual card itself. Switch to another card and you'll lose the maps - unless of course you had the foresight to load them onto multiple cards. Format your card as a lazy way to delete all the images and movies and you'll wipe the maps too. So if you're likely to fill more than a card's worth of photos on a trip and want to keep the mapping data available, I'd recommend bringing a laptop with you - at least you should also be able to use it to charge the camera. You'll also need to keep the DVD handy as the utility loads the maps direct from the disc."