Ellipsoidal coordinates

Ellipsoidal coordinates are a way of measuring where things are located on or near the surface of a sphere, like Earth. Imagine you have a globe of the world, and you want to give someone the location of a city or a landmark. You could say it’s at a certain latitude and longitude, which are both measured in degrees. But what if you want to be even more precise about where on the surface of the Earth that thing is located?

That’s where ellipsoidal coordinates come in. They use three numbers to describe the location of a point on or near the surface of a sphere: latitude, longitude, and elevation (or altitude). Latitude measures how far north or south of the equator a point is, longitude measures how far east or west of a certain meridian a point is, and elevation measures how high above or low below the surface of the sphere a point is.

But because the Earth is not a perfect sphere, but is instead a slightly flattened ellipsoid (a squashed sphere), there are different ways to define these coordinates that take the shape of the Earth into account. One common set of ellipsoidal coordinates is called “WGS84”, which stands for World Geodetic System 1984. This system uses latitude and longitude, but instead of elevation, it uses a measurement called “height above the ellipsoid”. This takes into account the fact that the Earth is slightly squished, so that the distance from the center of the Earth to the surface is different depending on where you are on the globe.

So, in summary: ellipsoidal coordinates are a way of describing where things are on or near a sphere, using latitude, longitude, and either elevation or “height above the ellipsoid”. Different systems of ellipsoidal coordinates can be used to take into account the fact that the Earth is not a perfect sphere, but a slightly flattened ellipsoid.