Why does the value of magnetic-declination radiance change by every running of calibrate_heading.cpp file?!!!

[Masoumehrahimi]

hi nick

Why does the value of magnetic-declination radiance change by every running of calibrate_heading.cpp file?
every time that i put the vehicle at the initial point and move it for 5 meters, the vale of magnetic-declination radiance is changing!!!

how to fix it?
thanks

[nickcharron]

See Important Notes point 2 in the readme. This calibration is a hack to fix improperly calibrated magnetomers. It does this by setting the magnetic declination to a value that would correct the wrong initial heading