To sharpen the quality of images in its Virtual Earth mapping application, Microsoft has signed a deal with DigitalGlobe's GlobeXplorer, a provider of aerial and satellite photos.

Over the coming months, Microsoft will integrate high-resolution images from GlobeXplorer into Virtual Earth, which in turn powers the mapping feature of Microsoft's local search engine.

The GlobeXplorer material will enhance about 400,000 square miles of US aerial images, Microsoft said.

The move is Microsoft's latest to sharpen Virtual Earth and its Live Local Search service, which competes against similar ones from Google, Yahoo, Time Warner's AOL and that also let users find local business listings and display online maps.

In November, Microsoft announced its intention to add 3D models of more than 100 cities to Live Local Search by this year's third quarter. The 3D models allow users to zoom into these metro areas and 'fly' over and into them using their web browser, something Microsoft rivals don't offer.

In May, Microsoft acquired Vexcel, a company that makes products for creating maps from aerial and satellite photographs, also to boost Virtual Earth and the local search engine.

Microsoft and its rivals have been busy improving their local search services because they have become very popular with users and advertisers alike.

In December, revamped and renamed its local search service AskCity, giving it the largest integration of IAC online services to date, including CitySearch, Ticketmaster and ServiceMagic.

Users find these search engines attractive because they contain business listings commonly found in print phone directories, but they complement the information with maps, driving directions and often include customer reviews, provide real-time traffic information and let people purchase movie tickets and make restaurant reservations online.

Searches performed on local search engines tend to be motivated by a desire to shop, which is very attractive for advertisers. Advertising revenue in local search engines is expected to grow from $3.4bn in 2005 to $13bn in 2010, according to The Kelsey Group.

In July, 63 percent of US internet users, around 109 million people, used a local search engine, up 43 percent from July of 2005, according to comScore Networks. Google nabbed 29.8 percent of those queries, closely followed by Yahoo with 29.2 percent. Microsoft came in third with 12.3 percent and was followed by Time Warner (7.1 percent), Verizon Communications (6.6 percent), (3.9 percent) and (2.7 percent).

The comScore study, released in September, found that during the second quarter of 2006, 47 percent of local searchers visited a local merchant as a result of their search behaviour.