So, I've recently learned about the Schiehallion experiment, performed in 1774, where scientists detected the deviation from the vertical of a plumb due to the gravitational attraction of a single mountain in Scotland. To choose the place, they surveyed for a large mountain as isolated as possible from any large masses and close enough for the expedition to make it cost effective.

I was wondering if there are any modern world maps of observed or predicted vertical deviations of a plumb. I guess they can be computed from elevation maps + rock density maps, but I'm unable to find one. There are many maps showing the gravitational anomalies but they only show how the gravitational acceleration changes and not the angle of the deviation in each place.

I would like to know what is the largest deviation possible on the surface of Earth (on land), and in particular what is the largest in Europe.

I guess that the shores of volcano islands like Tenerife might be good candidates since you have a huge mountain in one direction and almost nothing in the other. Also I guess the north of India where there are plains close to the Himalayas are also good places to think about.


1 Answer 1


I would say that in general, the vertical is defined by the direction of a plumb bob. There are three reasons that a plumb dos not point toward the center of the earth. One component of gravity causes a centripetal acceleration toward the axis of rotation. This effect can be calculated as a function of latitude. The equatorial bulge pulls the bob toward the equator. This effect is comparable but is more difficult to calculate. Regional variations, the focus of your question. I'm guessing this would be he smallest of the three. You might look for gravitational plots based on the variation of satellite orbits.

  • $\begingroup$ Sorry but this answers nothing. It just repeats what I said. I would like to know where to find a map for the deviation from the vertical because of gravity. I know there is a centrifugal effect and that there are maps of gravity anomalies made with satellites, I even mentioned It in my question. $\endgroup$
    – Swike
    Commented Dec 5, 2021 at 12:07
  • $\begingroup$ There's still the questions: How do you define “vertical”? And then, how do you measure a deviation from vertical? Given that, the only word-wide map would have to come from NASSA (or maybe Google). You might try their websites. $\endgroup$
    – R.W. Bird
    Commented Dec 5, 2021 at 16:36

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