Kansas City is avaialble at reasonably high resolution.(Source: Google Maps)

Coverage, Resolution and Watermarks
Recall that Google purchased Keyhole last year and dropped the access price to $29.95.Use of the provided orthoimagery with Google Maps requires no software download.After doing a search, users are presented with a link on the orange top bar with a link titled "Satellite." That turns on a satellite image of the area covered by the map.Coverage is limited to about half of the U.S.according to Keyhole's general manage, speaking to the Associated Press.One blogger reports "the satellite images are currently only available for North American addresses but will be introduced for other regions as the year progresses."

An area east of Kansas City reveals the edges of data sources.(Source: Google Maps)

The imagery is from DigitalGlobe and EarthSat.That leads to some interesting seams between different resolution images, and those acquired at different times of year.One area I viewed had vibrant sharp (high resolution) green fields on one side with a brown, fuzzy landscape on the other.The best resolution I found allowed the viewing of cars - so it's likely three meter data at best.Keyhole's website notes that it has high resolution imagery for certain areas, for example, down to 3" resolution in Cambridge, Massachusetts.That detail does not seem to be available via Google Maps.Further, what data are available are watermarked "© 2005 Google." While that may frustrate geospatial data users, from a commercial standpoint, Google is making the correct decisions regarding resolution choices and watermarking at this point.

Concerns and Limitations
Privacy advocates are concerned at least in part because Keyhole received some of its initial funding from CIA funded In-Q-Tel.(Many other companies in the geospatial space, including MetaCarta, have also benefited from In-Q-Tel funds.) The images are typically six months old or older, according to Keyhole's general manager.Google's Help simply states: "Satellite images are current, but not real-time."

No "flying" is available in this version; that requires the subscription version of Keyhole.Keyhole is noted for its "3D fly overs," which put the company on the map during the early part of the Iraq war.Still, panning and zooming with the images are as fast as with the old "map" option.

Expectations
Those following the announcement expect that this move will prompt Google Maps competitors to jump into imagery.Recall that MapQuest did have free imagery, from GlobeXplorer for a brief time, but the deal ended in 2004.MapQuest's FAQ regarding imagery simply provides a link to GlobeXplorer.Other mapping portals, including National Geographic's Map Machine and ESRI's MapShop, incorporate GlobeXplorer's technology and imagery.

The other company that should be concerned, some say, is Amazon's A9 search engine which recently began offering photos of the faces of businesses.I see that as a separate set of data; seeing the front of a business is quite different from seeing roofs.Recall that most people are very familiar with looking at businesses' front doors, but are less experienced in aerial imagery interpretation.

My Take
As many have pointed out already, Google is not the first to integrate imagery (from satellites or other platforms) into online mapping.Still, its implementation is easy to use and quick to display.While we in the geospatial community are concerned with timeliness of data and resolution and the like, the companies implementing these portals are interested in something quite different: revenue.

And, let's not kid ourselves, their revenues, be they MapQuest or Google or Yahoo!, are from advertising and paid services.They are looking to sell more ads and sign up more people to Yahoo Personals and the like.And that's fine.That's why Google Maps and this new implementation of Keyhole are free.

Still, each time Google ads new mapping related functionality (did you hear about the RideFinder?) it does raise the bar for every other player.So, does Yahoo's traffic data offer a bigger pull than free satellite maps? What about easy-to-follow "stick maps"? Or A9's block view? It's a big game of one-ups-manship to find the killer mapping app and capture visitors and ad dollars.The ultimate beneficiaries are both the companies who win and the map viewing public.

A Plug
I have the privilege of moderating a session at the upcoming Location Technology and Business Intelligence Conference with many of the mapping portal players.It's titled "Mapping Portals: Are they driving location technology into the enterprise?" and includes representatives from Keyhole (Google), MultiMap, Yahoo!, MapQuest and Microsoft.