Hola Jordi,
Did you already fly a plane (or your helicopter) with this? Nice project!
Saludos!
NO, but i used a lot of simulations like GPS simulator GPSSimul from Sailsoft combine with Google Earth PRO, and is very accurate, ill try to make a example video, to show that is 100% true.. 
For example you program you destination in Arduino, then in GPS simulator you put were you suppose to be (current position), then the arduino receive the nmea data, and display the heading. Then with GPS simulator you put the heading, and then the SPEED, and start moving directly to your destination (showed in google earth PRO).. Pretty exacting the first time i saw it working 