well if you can easily measure one point, then easily measure several points, fly a plane over these points and get a rough estimate of the distance. I mean this has been done, but for some reason its not valid, apparently.
Its just stupid. If you have a shape, you measure it, it is 2d and has 3 sides, each side is the same length, then you can make a pretty confident guess its going to be an triangle, its not going to be a pyrimid. If you measure the world, the measurments match those of a sphere, then its not going to be a circle.