If you have a fast PC and have not yet played with “Google Earth”:http://earth.google.com you are missing something astonishing. It has to be a PC, I’m afraid: there’s client software to download.
Essentially it is a set of satellite maps of earth, centrally served (You’ll need broadband, oops) and zoomable to various levels of detail. The highest level is astonishing. Not only could I pick out the exact hotel where I stayed in Cambridge in May, in Harvard Square I can distinguish individual people standing on the individually distinguishable steps down to the subway.
Even the next-highest level of detail, which covers London and parts of England, is phenomenal. I can see my own car outside my own house and my mother’s outside hers. I can trace (and measure) all my normal walks.
The next level is too blurry to distinguish individual houses or cars, but the overlay of roads on the countryside allows you to see where they are. In this way I am able to spot the house in the woods where I lived for three years in Sweden, and the farm where I will be this time next week.
What’s the use, apart from fun? There are all the usual overlays, showing where shops and banks and hotels and petrol stations ought to be, with all the usual biases towards the USA. But at the high resolution, it’s better than that. I can mark the pools that hold individual trout on the Cam. My friend Sean says this could ruin wild fishing in New Zealand. But I think it will be a while before that is mapped at the same resolution as Essex. Even in Montana, the rivers are a bit blurry for that sort of game. But, since I know so well the lakes I used to fish, I can pinpoint the bay where I caught my first ever trout on a fly.