Re the protocol for GPS, most OEM's are now making them with a serial data
interface known as NMEA 0183 (a US marine interface employing RS232 levels).
This is compatable with your computer serial port set to 4800 Baud but the
plugs on GPS's are all different and the manufacturers leads can cost many LLs.
BUT...............
The NMEA standard offers many ways to package the data in sentences and not all
OEM's use the same sentences to operate their gear. The very latest sub
assemblies from the US also now contain proprietry sentences to enhance the
possibility of products using the NMEA sentences and these will only work with
one manufacturer's software.
The answer is to try before you buy, although most moving map products will work
with most NMEA ported handhelds. Specialist Aviation suppliers (like RD
Aviation) do know which bit works with what and can advise you of any pitfalls
particularly rearding interfacing to VARIOs and other devices needing waypoint
info.
Gordon Lean
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