One of my long time projects back in the RCX days was to develop a rover which is capable to build its own map. Some of the bots in the Robots section take part in this project. The Tricycle as a study in extremely accurate steering, the Robotank V1 has the ability to calculate its own position by bearing the direction to 3 light buoys of know position - but it was unable of dead reckoning cause most of the sensor ports of the RCX where used by the scanner turret. So i build Robotank V2 as a accurate thread driven platform for 2 RCX bricks but the project went to sleep while other interesting things has to be discovered.

Now i think the time is right to make a new approach with the NXT. 4 Sensors ports without the necessity to waste sensor inputs for motor observation should be enough.

Planed capabilities of the NXT-Mapper bot: 

1. calculating its own position using dead reckoning 
   

2. calculating its own position by using 3 light buoys as a reference - used from time to time to correct the reckoned position.
   

3. detecting obstacles
   

4. Send the position of obstacles to a host via bluetooth