# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding

**Re: Coriolis Acceleration -- A general case**

**From:**Antoine Couëtte

**Date:**2018 Jan 8, 06:11 -0800

*Dear David*,

As complement to my post dated Dec 27th, 2017, and just by curiosity I dug out my [last millennium] student notes about the various airborne bubble sextant corrections.

In order to validly ignore the effects of ground speed magnitude variations let us consider here-after only constant magnitude horizontal ground speeds (e.g. GS = 457 Kts) in which only the Aircraft headings can change.

- When an Aircraft follows a
,*Great Circle**only*comes to play the Coriolis correction which is proportional to both the*Ground Speed*and to the*Sine of Latitude*. Hence the*Coriolis effect*is maximum at the Poles and zero at the Equator. The**Coriolis Acceleration Tables**are available and published in theand it is easy to verify that such Coriolis corrections are proportional to the ground speed itself.**Air Almanac** - When an Aircraft follows a
:*Rhumb Line*- The Coriolis
*instantaneous*correction is the same as above (i.e. no difference at all for an Aircraft having the*same*instantaneous ground speed vector and following either a Great Circle or a Rhumb Line, or*any*other curve actually). And: - To the "
*general and always applicable case*" of the Coriolis correction, an*additional and specific*Rhumb Line Correction is to be added. What is interesting to see is that such specific Rhumb Line correction is:*Proportional to the square of the Ground Speed*. And:*Proportional to the sine of the Ground Speed Track*, hence equal to zero for North and South tracks in which cases Rhumb Lines become Meridians therefore Great Circles. And also:*Proportional to the Tangent of the Latitude*, hence also equal to zero if Latitude stays at zero in which cases Rhumb Lines simply become the [Great Circle] Equator itself. Hence the Rhumb Line correction increases towards infinity when closing up from the Poles since it is proportional to the*Tangent*of the Latitude.- My handwritten notes also indicate for that for such Rhumb Line case Air Navigators preferably use the published
. Indeed, this point is fully covered in the "*Combined Coriolis and Rhumb Line Correction Tables*" document mentioned by*FAA NAV Course faa-h-8083-18.pdf**Gary*in a subsequent post on a different nonetheless related topic (*Re: HeadingSpeed-Acceleration-Error-Card-LaPook-dec-2017-g41054*) on that same day.

- My handwritten notes also indicate for that for such Rhumb Line case Air Navigators preferably use the published
- These
are also interesting to study since - after carefully removing the Coriolis acceleration effects and after correcting the remaining figures for round-off errors - you can hands-on verify that such*Combined Coriolis and Rhumb Line Correction Tables**specific Rhumb Line Correction*is proportional to the square of the ground speed itself as earlier mentioned here-above.

- The Coriolis

*Antoine Couëtte*