Survey based on the OSAM algo for rotorcraft. Instead of going from one
sweep line to the next with a line, a circle aligns the aircraft with
the next line.
Circles radius at the start of lines can be either automatic (sweep distance),
fixed or direct line (equivalent to original rotorcraft).
The code itself is reorganized to use a global structure instead of many
variables.
Gautier Hattenberger
dbed41784e