Coriolis & Eötvös Physics in Precision Ballistics

1. Introduction to Earth's Rotational Effects

At standard hunting ranges (under 300m), Earth's rotation is negligible. However, as shots extend to 1,000m and beyond—Extended Long-Range (ELR)—the few seconds of flight time are enough for the Earth to rotate beneath the bullet, causing measurable misses if not accounted for.

2. The Coriolis Effect

The Coriolis effect is an inertial force that deflects the path of a projectile when viewed from a rotating reference frame (Earth). For a shooter, this manifests as a horizontal and vertical drift.

Mathematical Derivation

In the Southern Hemisphere (South Africa), Coriolis causes a horizontal deflection to the left of the target, whereas in the Northern Hemisphere, it's to the right.

3. The Eötvös Effect

While often bundled with Coriolis, the Eötvös effect specifically refers to the change in perceived gravitational acceleration for an object moving relative to a rotating Earth. Shooting East makes the bullet "lighter" (less drop), while shooting West makes it "heavier" (more drop).

Calculation Formula

4. Practical Impact for South African Shooters

Shooting at 25° South (Pretoria/Johannesburg) at 1,000 meters:

• Horizontal Coriolis: ~3-5 inches of left drift.
• Eötvös (East/West): ~2-4 inches of vertical impact shift.

For a target like a 10-inch gong, failing to account for Earth's rotation can result in a 50% reduction in POH.

5. Scientific References

Our solver utilizes the 6-DOF models defined by Robert L. McCoy in Exterior Ballistics (1999), ensuring that every 10,000-iteration Monte Carlo simulation accounts for your exact latitude and azimuth.

Apply This Knowledge

ONESHOT Ballistics handles these complex physics calculations automatically using your device's GPS and compass.