Question : GPS design help required

Hi,
I'm working on a vechile tracking sytem with GPS.
I have database of all the stops enroute. At predetermined frequency I have to report the current velocity and position and distance to the next stop to the user. My question is How to determine the distance to the next stop. As GPS gives only straight line distance how to take care of deviations in the route. Also how often i need to process the NMEA strings to update hte distance travelled.

Thanks in advance
Srujan

Answer : GPS design help required

Hi Murphey,

Thank you. Could you point me to a source containing the process of calculating distance from lat/long.  As I'm poling every second or so ,I can just apply pythagoras theorem, am I right?

Regarsd,
Srujan