Hacking TerraServer
I recently wanted to see some old satellite photos of my neighborhood.
As far as I know, you can’t do this with
href="http://maps.google.com">Google Maps, but you can with
href="http://terraserver.microsoft.com/">TerraServer (which
predates Google). I start with a URL like this:
href="http://terraserver.microsoft.com/Image.aspx?T=4&S=8&Z=10&X=11028&Y=105601&W=2">http://terraserver.microsoft.com/Image.aspx?T=4&S=8&Z=10&X=11028&Y=105601&W=2.
Breaking down the querystring, we get:
- T - the theme indicates the photo set you would
like. 1 contains USGS photos from the early 90’s, 2 is USGS topo maps,
and 4 is circa 2002 USGS satellite photos. - S - the zoom level ranges from around 8 (0.25 meters
per pixel) through 19 (512 meters per pixel), depending on target
coordinates and image source - Z - the scene apparently should always be set to
10 - X - the x-offset seems to be a function of zoom
level, so you can’t simply change the S parameter and expect it to
zoom appropriately because the X and Y coordinates will have
changed - Y - the y-offset - same caveat as X
- W - the image size - small (1), medium (2), or large
(3)
Some additional poking could be done to understand whether scene 3
exists and what it contains and to understand the relationship of
zoom-level to x and y coordinates, but I was content to get the 1990
images from around my house.