Google has upgraded with a geolocation API its Gears browser plug-in, which is designed to let users work with Web-based applications when they aren't online.

The new API (application programming interface) will let developers create applications that can obtain information from Gears about end users' geographic location, Google said Friday.

To protect people's privacy, the Gears Geolocation API triggers an alert asking users if they wish to grant the application their location information.

Currently, the API allows mobile devices to obtain the location data from nearby cellular towers or on-board GPS systems, and later it will be able to detect Wi-Fi connection coordinates on both desktop PCs and mobile devices. For now, only some Windows Mobile devices that can do GPS or cellular tower identification are supported, but Google expects to bring more mobile platforms into the API's fold.

Knowing where a user is located opens the door to entirely new types of applications and allows developers to build additional functionality in existing Web applications.

The geolocation API is one of several enhancements in version 0.4 of Gears, a product Google released in May of last year to tackle the problem of offline access for Web applications.

While online applications have become increasingly popular as IT and business managers give more consideration to SaaS (software-as-a-service) products, a big drawback has been the loss of functionality when users don't have an Internet connection.

Different options are available, but Google hasn't been particularly quick at adapting its Web services and software to Gears, making it available so far only for its RSS feed manager Reader and its Docs applications.

Zoho, a competitor to the Google Apps collaboration and communication hosted suite, also uses Gears for offline access in its suite, while Yahoo's Zimbra has its own technology called Desktop.

Other enhancements in Gears 0.4 include a Blob API for referencing arbitrary binary data, an extension of the desktop API and localization of Gears dialogs in 40 languages.

Google also announced the AJAX API property that lets Web applications estimate users' locations using their IP address.