Details below routes and costs are provided so intuitively that instructions are not needed. Overall, it’s an excellent example of a first-rate information application.

That has changed. Computers have added another dimension to mapping. In 1967 Roger Tomlinson of the federal Department of Energy, Mines and Resources in Ottowa, Ontario, developed the world’s first operational GIS (geographic information system ) that was used to store, analyse and manipulate data collected for the Canada Land Inventory. In essence, Tomlinson had married a database to a map so that layers of information could be bound to spatial coordinates. Until recently, good GIS tools belonged only to governments and the corporations that could pay for them.

Yesterday afternoon I downloaded the free version of Google Earth and started my own GIS. Google Earth is a viewer that allows you to access terrabytes of satellite and aerial imagery simply by typing an address. Not only can you view the street where you live, but you can create your own personal topography by adding annotations to maps and sharing them with other viewers.

Since Google acquired satellite mapping company Keyhole in October of last year, the subsequent Google Earth offering has been in beta, or testing stage. As with Google Maps, the search engine giant made the API available to developers. What this volunteer army of coders comes up with will likely shape future mapping products from Google. Although, the company is reportedly already working on products for the real estate and travel industries.

Meanwhile, new applications created by tying Google mapping functions to existing databases are popping up all over the net. In San Francisco a group called NextBus has used the Google maps and transit department GPS information to display real-time locations of busses all over Fogtown. Another user has mapped Lewis and Clark’s transcontinental journey onto the Google Earth. Several blogs track the developments. Two of the best are Google Maps Mania and Google Earth Blog.

Google Earth runs in a separate viewer (an 11MB download) whereas Google Maps runs within the browser window. GE users are swapping XML files (actually, XML-based KML, or Keyhole Markup Language files) to present information; while Google Maps webmasters show most of their info with native JavaScript, although XML files can be imported. Both GE and GM are relatively simple to use, which accounts for their popularity.

Because these tools are so new they are a bit sketchy in places. For instance, Google Earth is great for urban areas, but rural locales aren‘t covered in any detail. Also much of the satellite imagery is three years old. However, that will change with the launch of two new DigitalGlobe satellites starting next year. Both geo-imaging orbiters will be capable of ground resolution down to half a meter. Finally, the separate viewer application for GE is a bit awkward. If Google’s computer engineers could recast the viewer as a browser plugin, it would have a much greater utility.

Any article on free satellite imagery would be remiss without mentioning World Wind, NASA’s fabulous viewer. In terms sheer visual information, World Wind blows GE away. World Wind draws on the LandSat libraries, USGS information and Shuttle Radar Topography for incredible bird’s eye views of the earth, and MODIS data, which is updated daily. If NASA provided an open-source API to the public, who knows what would develop.