Your Location without GPS
The blogosphere have widely covered the release of My Location service for Google Maps for mobile. It uses GSM cell tower identifications to provide an approximate localization of a mobile device. Thus it is posible to develop Location Based Services in mobiles without GPS. Google also has announced the two ways to use these new functions programmatically, over the Android OS and with Google Gears for Windows Mobile.
The following video explains this idea:
But this idea is not new and perhaps it is not the best option.
Three main technologies can be used in order to estimate a location.
- GPS. The number of mobile devices with GPS capabilities is increasing fast. GPS provides 10-15m accuracy, which is good enough for most of applications. The drawbacks of this technology are: it is slow, it consumes a lot of energy and its coverage is poor or null in dense urban areas and indoors.
- GSM cell towers identification. Knowing the location of GSM cell towers it is posible to guess a mobile position with an accuracy from 200 meters to 1 km. My location service from google uses this information. A database of cell towers positions is needed. The open source project OpenCellID aims to create a worldwide CellsID database with their location.
- Wifi positioning System. The position of WiFi access points also can be used in triangulations to guess a device localization. Its accuracy is better than GSM triangulation, but it is more expensive to mantain an updated database of working WiFi access points and their locations. Also the coverage of WiF positioning systems is limited to urban areas.
Obviously, a combination of these three techniques can get the best results. Two main companies have developed solutions taking the advantages of Wifi, GSM and GPS localization:
- Skyhook’s hybrid positoning system (XPS). This solutions are used in the new iPhone 3G and in Navteq systems.
- Navizon virtual GPS. It also combines Wifi and cellular triangulation and can be bought for 25$. A commercial SDK is also available.
December 19th, 2009 at 11:40 pm
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