Lens with Angular Markings (Attachable)

Before getting to the Idea, here is the problem it hopes to solve.

I live in a place where jets fly above, and make a lot of noise. Some years ago I discovered that there was a Rule to the effect that the jets were supposed to fly at least 1000 feet (about 305 meters) above the ground, but they actually often fly only a little higher than the tree-tops.

Now, consider the Inverse Square Law. If a noise is generated 1000 feet off the ground, and an equal noise is generated at half that altitude, the noise-energy received at the ground is 4 times higher for the lower-altitude noise generator.

If the plane flies at 333 feet (1/3 of 1000), the noise- energy will be 9 times higher than from a plane at 1000 feet.

Trees generally don't grow as high as 100 feet around here, so planes can fly fairly safely at 100 feet (1/10 of 1000) and thus the ground receives 100 times the sound- energy as from a plane flying at 1000 feet.

To be fair, there is another factor, in that human hearing is "logarithmic", not "scalar". Encountering 100 times the noise energy is not the same as experiencing a 100- times- louder sound. Nevertheless, the lower-flying planes are certainly louder!

The military presence in this town extends into its political life; there are a lot of retired people here who don't mind the jets making all that noise. So, there is no easy way to enforce the 1000-foot flying Rule. That's where this Idea comes in.

One well-known way to measure the distance to something involves its "angular diameter". Consider a TV --if you sit far from it, it appears smaller than if you sit close to it - - but you know it is the same size. Your overall "field of view" has less of it occupied by the distant TV than is occupied by the near TV. You can imagine an angle from your eyes to the left and right edges of the TV; that angle is smaller for the distant TV.

Now imagine a camera lens engraved with angular markings, rather like the circles of a bulls-eye. Any image you make will include those markings in the finished photograph, and no matter if the finished photo is enlarged or shrunk, the markings will accurately indicate the degree to which something in the photograph occupies the field of view.

So, take a picture of a jet flying by, at some modest distance, maybe a half-kilometer. The physical dimensions of the jet are public knowledge, and your picture now includes its angular diameter. You can use those two data items to compute exactly how far the jet is, away from the camera.

More, there is another angular measurement in the picture, the height of the jet off the ground. When you know the exact distance of the jet, that height can be computed easily. So now you have evidence you can take to the Legal System, to make the case that the pilots who don't fly at least 1000 feet can be caught and punished.

(Lenses marked as described here almost certainly exist. I'm asking that ordinary/common cameras, like on cell phones, be given an easy way to attach such a lens.)