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News Flash

Jan 2022: Release of app update.

Feb 2021: Added Utilities to calculate Stability Factor, Spin Drift, Coriolis and Eotvos effects, and speed of sound. 

Eötvös Effect

The other Earth Rotation effect of interest in ballistics is the Eötvös Effect.  It is an east/west effect that produces a vertical deviation from the target.  Shots in an easterly direction impact high, and shots in a westerly direction impact low.  It is dependent on both latitude and azimuth (compass direction).  It is maximum at the equator, shooting either straight east or west, and vanishes to zero at the poles.

deflection (ft) = 0.000072722 * distance(ft) * Cos(latitude) * Sin(azimuth) * time of flight(seconds)

All values must be entered by the user. Otherwise zeros will result.


Latitude (degree)
Azimuth (degrees)
Distance (yards)
Time of Flight (seconds)



Eötvös Effect (Feet) + POI High, - POI Low


The vertical deviation in MOA is calculated using the Teunissen Equation, developed by ameteur Dutch physicist C. Teunissen. The beauty of this equation is that the answer is directly usable in a scope with bullet drop marked in moa. Deviation (moa) = 0.25 * tof * cos(latitude) * sin(azimuth)


Deviation (MOA) + POI High, - POI Low