Oh yes.. actually the GPS is not for the arducopter, is for arduplane, but if you wish to use it in arducopter (for navigation only, no for stabilize)you need to use kalman filters, magnetic compass, and accelerometers. But arduino cant handle it. Maybe in the future when arduino 16 bits or 32 bits born, could do it.
The arducopter project is just Gyros+accelerometers+Kalman filters to stabilize the heli.
Right now im concentrating myself in the Arduplane project, because is cheaper
, latter when my income increase i will buy a better Heli and try again.
-My investigations about the IMU (Inertial measurement Unit) can be used by helicopters and airplanes too. Is the most difficult thing about automatic pilots. Almost done.
-The GPS is done.
-Altimeter, is solved, ill use sparkfun altimeter with SPI. (resolution of 15 centimeters for unit).
-Servo control is done.
Mixing this (IMU,GPS,Altimeter,Servos), you are able to do a fully autonomous R/C airplane.
-Modem to send data to ground, done.
-Ground Station, done.
Another thing you might wonder is about switching between autopilot mode and manual mode. Well is a little bit complex to explain (with my low English skills), but ill use a mechanical switch (to void any possibility of lost control if hardware fails). I show you: