> How large would you expect the errors to be ? He's aiming for
> 10 - 15m positional accuracy updated every 15 seconds

I found out at last under an NDO what the application is. As expected,
there's a much better alternative to what he originally proposed. My
suggestion to him now is to have the GPS unit fitted with a small AM
receiver that can be contacted to request position. It also transpires
that even an hourly request is sufficient, not every 15 seconds. As the
GPS module itself can be powered-down for long periods this means
a substantial reduction in battery power and makes the product viable

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics