Coriolis Effect
Definition
Apparent deflection of a moving body due to the rotation of the Earth. In the Northern Hemisphere, deflects projectiles to the right (for any direction of travel); in the Southern Hemisphere, to the left. Magnitude proportional to latitude, velocity, and time-of-flight.
- Cause
- Earth's rotation
- Northern Hemisphere deflection
- To the right
- Southern Hemisphere deflection
- To the left
- Scales with
- Latitude, velocity, time of flight
Common questions
At what range does Coriolis deflection start to matter for a shooter?+
It becomes a practical correction mainly at long range, where time of flight is long enough for the small per-second deflection to accumulate into inches or more at the target, which is why it matters for extreme long-range and sniper reconstructions but rarely for typical handgun-range incidents.
Is Coriolis deflection the same at the equator and near the poles?+
No. The effect is weakest near the equator and strongest near the poles because it scales with latitude, so the same shot fired at high latitude deflects more than an identical shot fired near the equator.
Related terms
- 4DOF Model
- A four-degree-of-freedom ballistic model that adds aerodynamic pitch and yaw to the standard 2DOF (gravity + drag) model, accounting for spin drift...
- BDC (Bullet Drop Compensator)
- Elevation turret or reticle markings that encode the required elevation correction for a specific load at preset ranges. Allows rapid correction without...
- Eötvös Effect
- The vertical component of the Coriolis effect on a bullet. Increases impact elevation for eastward-fired shots, decreases it for westward-fired shots. Typically...
- Fire Control System (FCS)
- An integrated optic, rangefinder, and ballistic solver that computes and displays a real-time firing solution. Examples: TrackingPoint PGF, Elbit FALCON, Rafael MARS....
- Laser Rangefinder (LRF)
- A device that measures range by timing the return of a laser pulse from the target. Typical accuracy: plus or minus 1...
- Magnus Effect
- A force on a spinning body in a crosswind perpendicular to both the spin axis and the crosswind direction. Produces a vertical...
- Miliradian (Mil)
- 1/1000 of a radian. Equal to 10 cm at 100 m, 1 m at 1,000 m. Used as the angular unit in...
- MOA (Minute of Angle)
- 1/60 of a degree of arc. Equal to approximately 2.908 cm (1.047 inches) at 100 m. Used in civilian and some law...
- Spin Drift
- Consistent lateral drift of a bullet in the direction of rifling twist, caused by gyroscopic precession of the bullet's nose around the...