Easy math puzzles

To determine the width of the tank from a single point, no measured angles, I think you’d need to know the distance to the tank. Then you could do it by measuring how much of a fixed object (at a fixed distance) it blocks from sight

Quote: Ace2

To determine the width of the tank from a single point, no measured angles, I think you’d need to know the distance to the tank. Then you could do it by measuring how much of a fixed object (at a fixed distance) it blocks from sight
link to original post

I don't think you could do it without measuring angles, being you can only see the endpoints of a perpendicular diameter across the tank at infinity.

There are ways to measure radii of curvature optically, like the way you would inspect a lens or curved mirror. If I had a lens bench and some sample lenses I could do it. Might even be able to do it with a surveyor's transit, see what I have to do to keep the telescope in focus when looking at a different point on the tank.

The surface of the tank makes a difference too. If there were markings or gradations on the tank that would help, even if it was just a chip in the paint. If it was a perfectly uniform Lambertian surface all around there would be no visual distinction between any two points on the tank, not sure what you would do.