Techniques used to establish the height of a mountain or the depth of a precipice on Earth are of little use on other planets. And it is that, in our world, to measure geographical accidents, the average sea level is usually taken as a reference. However, this is not possible when trying to establish the depth of a lunar crater, the height of a Martian hill, or the dimensions of a mountain range on any other planet.
To find out, astrophysicists must measure the body in question and calculate a mean polar and a mean equatorial radius . With both data, a theoretical spheroid is constructed that is used as a reference level for the measurement of heights. The surface of the spheroid is taken as the zero point , so any other located below it will be considered as a negative height, that is, a depression. Likewise, any level that exceeds the zero reference point will be marked as a positive height, that is, a mountain.
