How to use a graphic flight computer to find ground speed and true heading<br>Align the wind direction under the " true index " mark by rotating the azimuth plate. If the winds are from 330 ° at 20 knots, align 330 under the true index. Align the grid so the center grommet is over one of the heavy lines.
ground speed and true heading can are best found with a graphic flight computer
The context only states it is a way to do measure flight speed, not that is the best. There might be a better method. The system could likely not interpret the use of the word best as meaning the top method. 
( z1 possible :ARG1 ( z2 find :ARG1 ( z3 and :op ( z4 speed :mod ( z5 ground ) ) :op ( z6 heading :ARG1-of ( z7 true ) ) ) :instrument ( z8 computer :mod ( z9 fly ) :mod ( z10 graphic ) ) :manner ( z11 good :ARG2-of ( z12 have-degree :ARG1 z2 :ARG3 ( z13 most ) ) ) ) )