Horizontal Coriolis Force: Calculation
Equation
To manually calculate horizontal Coriolis deflection, we only need to know the latitude of our position and how long our bullet will be in flight:
(.00007292 rad/s * cos(latitude°)) * (Time of flight) * 1000 = Horizontal deflection in MRADs
Where:
- positive outputs = right deflection
- negative outputs = left deflection
Data collection
Time of flight can be found in the ATragMX under the “RC” button in the top right of the screen or derived in an online ballistics program. As the ATragMX suite is not available in situations where manual ballistics are relevant, time of flight information should be recorded prior to operation start.
Map latitude in Arma 3 does not always correlate with real word locations, rather this information is manually populated by map makers and is persistent for an entire map. Latitudes for common UNITAF campaigns are listed below:
| UNITAF Campaign | Map Name | Latitude |
|---|---|---|
| Operation Black Flag | Takistan, Takistan Mountains | 35° |
| Operation Deadlock | Lingor v3.9.5 | -4° |
| Operation Everglade | Rosche, Germany (2.0) | 53° |
| Operation Everyman | Armavir | 44° |
| Operation Fault Line | Lythium | 34° |
| Operation Fulcrum | Uzbin Valley | 34° |
| Operation Guardian Angel | Island Panthera | 46° |
| Operation Hetman | Livonia | 54° |
| Operation Honeybadger | Reshmaan Province | 35° |
| Operation Polaris | Altis | 40° |
| Operaton Quantum | Kingdom of Regero | 39° |
| Operation Steadfast Resolve | G.O.S. Al Rayak | 36° |
| Operation Valiant Guardian | Beketov | 55° |
Calculation Example
Sgt McShooty is deployed as a Spotter (Manual) on a Honeybadger. He ranges a priority target at 900m, a shot that will have a time of flight of 1.8s.
(.00007292 rad/s * cos(35°)) * (1.8s) * 1000 = .11 MRADs
Because the output is a positive value, the bullet will deflect .11 MRADs to the right due to horizontal Coriolis.
Equation limitations
This equation will serve well under most conditions and the small degree of inherent error will not impede operations in target rich environments.
In high value target environments, or when the effects of a single shot must be guaranteed, it should be noted that this equation does not take into account smaller influences on Coriolis drift, such as changes in latitude and atmospheric conditions. Under extreme circumstances, this can create relevant error when factored alongside other unknowns. In general, this equation overestimates the effects of horizontal Coriolis deflection, between .02 - .04 MRADs at typical distances up to 1000m. This error increases as distance increases.
If the effects of a shot must be guaranteed, decrease the equation output as distance increases.
