A dead reckoning (position) library (for NXT & robotc) to try out. It maintains global variable as to your robots location and heading without a compass, although a compass will help make it more accurate. And provide simple Piloting functions like move, turn, goto(x,y).
Please let me know of any problems you run into. I'm still working on a video explaining it, but as is usual for me, I got carried away and I am trying to do too much. (see update)
http://www.spiked3.com/?p=410The zip file has the LDD for my bot, but the library is generic and should work with any differential drive robots. Let me know if it does not.
update: man, this project has been a pain. I've been calling it localization for a while, and forgot, it's not really, it is dead reckoning. Localization involves using something in the environment to correct dead reckoning errors. So, even though I got a second wind to work on the video tutorial, I now have to go back and fix a bunch of voice overs. I gave up on finding something to use as a whiteboard. Any suggestions? Have you seen and/or know how they did the latest udacity videos?