ast articles have discussed how to interface with GPS receivers to obtain the geographical position of a device and then transmit the information over to a server for mapping purposes. However, not all mobile devices today have built-in GPS receivers. Moreover, GPS does not work in-doors. This seriously limits the usefulness of applications built around GPS technologies.
If you don't have GPS, or it's unvailable, a good alternative is to obtain the ID (often known as the CellID) of the base station to which your device is currently connected. As the mobile device moves from one position to another, it generally connects to a base station that offers the best signal (though this decision can be based on a number of criteria). Once the CellID is obtained, you reference a database to obtain the geographical location of a base station and thus deduce the position of a mobile device (to a certain degree of accuracy).
There are two steps involved in using CellID to find a device's location:
- Obtain the CellID of the base station to which the device is connected.
- Resolve the CellID into latitude and longitude.
This article will show you how to build an LBS application using a Windows Mobile device and Google Maps.