NavList:

Another approach would be taking the angle between the shadow of self and the horizon; the local altitude of the Sun, in fact. Assuming the camera ("self") is somewhere around the bottom of the "body" of the vehicle, this angle comes out to about 370px ≈ 10°, and the height of the "eye" is about 1m above the horizontal plane on which the legs are resting. The intersection of the shadow with the plane is then about 6m away.

This is a 50% difference from my previous estimate but at least it's within one order of magnitude. That's probably not surprising, given the crudeness of the methods.