توضیحات:

MeasureTAS provides a simple way for a pilot to determine the true airspeed of an aircraft to GPS accuracy. The technique is to fly legs in three arbitrary directions (preferably 90 - 120 degrees apart) while MeasureTAS captures GPS track and ground speed values for each leg.

The arrow indicates the current leg. Allow several seconds for TRK and GS values to appear. When the TRK and GS values for the current leg stabilize, tap the arrow to capture them. After the values are captured for the third leg, MeasureTAS calculates and displays the true airspeed. Units (Knots, MPH, KMH) can be changed at any time.

The algorithm used in MeasureTAS was developed by Doug Gray and published in 1998. A copy of that paper is available here: https://drive.google.com/file/d/0B_bzzDSY9OsSSU91ZV9OREFaWTA/view