Collection and use of uncertain data in a mobile GIS

Abstract

This study looked into the possibility of saving power in mobile geographical information systems by extending the interval between GPS updates. A J2ME application has been developed to test this theory. Via a map it can guide the user to his destination. The program displays the current uncertainty of the user’s position. This uncertainty spreads out until the next GPS update is received. To make the long update intervals transparent to the user, a dead reckoning scheme was included. The application tries to guess where the user is, based on different input like the previous position or data from the phone’s accelerometer. Both the spreading of the uncertainty and the dead reckoning has different implementations for driving and walking. The tests of the application showed that the phone battery lasted approximately 4 times longer when going from 2 seconds GPS update intervals, to only updating when the uncertainty exceeded 500 meters in diameter. The results lead to the conclusion that extending the update intervals is a great way to achieve longer battery life for mobile applications which rely on a GPS receiver.