On Thu, 17 May 2012 10:45:54 -0700 (PDT), "
wrote:

On May 17, 12:59*pm, Karl Townsend
wrote:


GWIW, I use these tractors to spray pesticides and fertilizers.
Accurate spped is very important.

karl

Have you looked at gps receivers? The one with some augmentation as
WAAS might be accurate enough. There is a thread on
sci.electronics,design labeled

Testing the Dealextreme ET411 GPS module


I would think this is a common problem for farmers and Jan might be
interested in developing a system for accurate slow speeds for farmers
needs.

Dan

Rockwell has been flogging systems for farmers for years. Dunno how
expensive they are.