Getting a bird's-eye view of any place on Earth

Map-reading travelers know that gaining a high perspective is an important element in finding your way around places, both familiar and strange. The broad views from atop tall structures and panoramic high points provide an opportunity to get a different lay of the land.

Now it is possible literally to have the entire planet at your fingertips.

Over the last two years, a software product originally created as "Earth Viewer" by Keyhole, a company acquired by Google in 2004, has provided anyone with a good computer and fast Internet connection with the ability to get a bird's-eye perspective of practically any place on Earth.

Renamed Google Earth, its basic virtual globe program can be downloaded for free onto a computer (earth.google.com). More sophisticated versions can be purchased for professional uses.

These systems access available data bases of high resolution, high-altitude images obtained from satellites, aerial photography and GIS (geographic information systems) to provide clear pictures looking down on a given place.

The degree of resolution varies, but in many major cities, it is high enough to provide clear images of individual buildings, the color of cars on the street, even shadows of pedestrians.

Users can search the data base by address or geographic coordinates, or simply scroll across a map of the Earth and zoom in on a particular location. Once there, the image can be scrolled to find your way over a particular location.

Even more amazing, Google Earth uses NASA's digital terrain modeling to provide images that have three dimensions and can even be rotated to get different perspectives.

Of course, these satellite images are not real time. (You can't just wave out the window and expect to see yourself on screen. Wouldn't that set off a storm of privacy issues?)

Generally the photos have been captured within the last three years, on clear, sunny days, when a minimum of foliage is blocking the view.

You can get a very clear overview of a place, including the layout of streets and general topography. Street map overlays can be added to put names to places. What better way to familiarize yourself with a place you'll be visiting?

Photo images and map overlays can be customized and combined with other information, incorporated into other documents, shared with fellow travelers, even transmitted to portable electronic devices and cell phones for use on location. How cool is that?

Then last May, another geographic Web portal, WikiMapia (www.wikimapia.org) was launched by two young Russian scientists, Alexandre Koriakine and Evgeniy Saveliev, with the aim of "describing the whole planet Earth."

This site accesses the same images as Google Earth, but does it with an online system that doesn't require downloading any programs.

While not as sophisticated as Google Earth (no 3D images or different perspectives yet), WikiMapia does seem simpler for a casual or novice user and is easier to navigate.

Furthermore, the site incorporates a wiki system, which allows registered users to stake out a particular place, provide personalized descriptions, commentary, photos, even video to bring it to life.

Since WikiMapia went live a little more than seven months ago, users have identified more than 2.5 million places.

The two systems can even be used together to provide greater detail and flexibility.

Both of these resources are powerful and fun mapping tools that can provide travelers with valuable insights about geographic locations they'll be visiting. They're also great for getting a better image about places both close at hand, as well as those you'll be visiting only in your imagination.