Last week, I discussed of a couple of Web-based Geographic Information Systems (GIS) produced by government departments. Reader Brandon Fouts pointed out that Google's new map service is worth checking out as well.

It turns out that not only are Google Maps (see editorial links below) pleasing to the eye, but they are also pleasing to the inner geek. The service, which uses nothing more heady than DHTML, uses some clever techniques to make map delivery and manipulation very fast.

For a really interesting and thoughtful discussion of the techniques used, check out the article on Joel Webber's blog (his blog is named "as simple as possible, but no simpler / Questionable wisdom from someone building weird but wonderful web technology").

In Google Maps, note the overlay graphics that cast shadows. Webber's blog article points out that the graphics are PNGs with 8-bit alpha channels. He writes: "Personally, I didn't even realize you could depend upon the browser to render these correctly, but apparently (at least with IE6 and Mozilla), you can." Also note that some of the techniques used seem to cause problems for the Opera and Safari browsers.

Google Maps enables users to go to a location ("10 market st, san francisco"), find a business ("hotels near lax") and get directions ("jfk to 350 5th, new york, ny"). Users can also click to the center of the map, drag the map, zoom in to street level and zoom out to the entire U.S.

Reader Fouts also reminded me of another Web site with applications that are very interesting and well done: NASA's J-Track and J-Track 3D. These are Java applet-based services that show you graphically the positions of most of the satellites, including the International Space Station and the shuttle (when it is flying). J-Track plots the positions on a flattened map of the earth while J-Track 3D renders a 3D version of the same data. Very cool.

Mark Gibbs is a consultant, author, journalist, columnist and blogger.