# Eotvos effect - Apparent only?

Hi all,

To get straight to the point of my question, is the Eotvos effect purely an 'apparent' effect?
i.e. it only arises if you choose a biased reference frame that is fixed to the surface of a rotating object (in our case the spinning surface of the earth)?

From my understanding of the article that I read on Wikipedia, it seems like it would only be worth discussing if your frame of reference is on a spinning surface relative to some other absolute coordinate system....is that roughly a valid statement, if not, what is incorrect about that statement?

Somewhat further to that (/as a refinement of the above), is it in any way incorrect to state that the Eotvos effect is actually completely accounted for if you correctly account for the Coriolis Effect? (the latitudinal component of the Coriolis effect in particular?)
....It seems to me that the East-West latitudinal component of the Coriolis effect is really just another way of expressing the Eotvos Effect - or vice versa - when your frame of reference is fixed to a spinning object, all of which is being measured against some fixed coordinate system...

FYI: I ask this question from the context of external ballistics, which is to say that it is related to correcting for the trajectory of a projectile when fired from (and hopefully intercepting) another location on the earth's surface.

Thanks

A.T.
it only arises if you choose a biased reference frame that is fixed to the surface of a rotating object (in our case the spinning surface of the earth)?
Yes, it's the consequence of using a non-inertial reference frame. See also:

http://en.wikipedia.org/wiki/Fictitious_force

....It seems to me that the East-West latitudinal component of the Coriolis effect is really just another way of expressing the Eotvos Effect
No. The Eötvös effect is the vertical (surface normal) component of the total Coriolis effect. In some contexts "Coriolis effect" refers only to the horizontal components, and the vertical is called Eötvös.

I ask this question from the context of external ballistics, which is to say that it is related to correcting for the trajectory of a projectile when fired from (and hopefully intercepting) another location on the earth's surface.
If you want to do your ballistic computations in the non-inertial frame of the Earth, but still use Newtons 2nd Law, you have to introduce inertial forces:

http://en.wikipedia.org/wiki/Rotating_reference_frame#Newton.27s_second_law_in_the_two_frames

Note that there is no Eötvös force in the above formulas. It is included in the Coriolis force

Last edited:
Okay, thanks very much for the clarification.