SIFL: Getting Started - Mileage Calculation in Company Data
FOS uses the great circle distance between airports to calculate the SIFL charge.
This setting can be found in the Company Data under the “Times” tab.
Spherical– this option will calculate mileage as if the earth is a perfect sphere.
Ellipsoid (Vincenty)– this option will calculate mileage based on the earth being an ellipsoid and not a perfect sphere. This is the recommended option.
If you are changing this setting within FOS from “Spherical” to “Ellipsoid”, ensure you input an effective date so that past scheduling data does not change.
Note: If the SIFL cost is calculated in FOS and you also use another method to compare the result, ensure the calculation outside of FOS is using the same distance calculation as set within FOS or the resulting answer may be different.