> So all he needs is a PIC which will take the current location, output by
> the GPS, and calculate the distance to a known set of points, triggering
> an alarm when a trap is within .5km or something?
>
> Since the distances are so small, one could even ignore the great circle
> equations, and go straight to the square root of the sum of the squares
> of the differences in latitude and longitude.  Could probably perform a
> few tricks there as well using tables, or by alarming when both lat and
> long are within one mile of the trap's lat and long.  Since the GPS only
> updates every second, it'd have a full second to compare the current
> position with the table of traps, which is plenty of time.
>
> The hardest part, in fact, would probably be the serial reception and
> NMEA parsing, and deciding how to store the trap coordinates.
>
> Of course, it would be better to use APRS and a radar detector so you
> could warn others of mobile speed traps you find as well.

Alternatively you could try obeying the speed limit.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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