Dead reckoning is useless outdoors. The wheels grind and slide and hump over gopher mounds or rocks. Even worse for big machinery, farm machinery wheels slip and slide in loose durt. Might work OK on carpet though. My goal in this is a yard-sized project. I have a mowbot in the works that is designed to use random mowing algorithm (blundering about) and bump sensors inside a fenced yard. That works OK for the back yard, but the front yard will require an expensive fence or a different idea such as local positioning. So my range is on the order of 150'. Ultrasonics might not work so good in a farm-sized operation - they might not have the range for a farm field. Having raised a little wheat and soybeans, I think about this problem some. -- Lawrence Lile Hopkins Sent by: pic microcontroller discussion list 11/11/2003 09:40 PM Please respond to pic microcontroller discussion list To: PICLIST@MITVMA.MIT.EDU cc: Subject: Re: [EE:] GPS vs LPS There is a system called dead reckoning in witch you start your robot of at a know location and us a gyro to sense every movement along with a distance recorder - like a Speedo. The Gyro will give you an output that can be translated into degree's. I have seen cheap gyros sold for robot systems. I do not know how accurate they are but could be a starting point. This is a simple system and with an accurate gyro & distance recorder you will have accurate results. This is how plains, ships & submarines can passively keep track of where they are, is no radio transmissions required that the enemy may hear or block. :-) Roy -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu