You're only one person dude, you aren't "we", 18m is on the lower end of things.
Dude I ain't Charmander, what he said isn't what I said, you're talking with me, leave him out of this, I agreed it was above 10m, because it is, I said then we should take a look at the other shots and see if we can get a value, I never said flatout "yeah let's use 1/3", I'd probably go with 1/4th if nothing could be salvaged from other shots, but that isn't the case. We can very well calc the depth in many shots, the issue is picking which one to use or what's most consistent in regards to how the hole is portrayed. (Honestly, I'd say we should check the anime in this case, the anime tends to have the sizes of things remain more consistent between shots opposed to the manga were it could increase and decrease by a whole magnitude).
But the formula I used? The Basic angsizing formula? This formula?
Object in pixels
Screen height in px
Object size in value
Object Height*Panel Height/(Object in Px*2*tan(70deg/2)) =
The most basic of things? Do you really not know how to do this? I just took Youpi and angsized how deep he was into the crater, got like 17-18m, using a lower end height for him. Could be higher, but again that's ONE shot, could get higher depending on the panel.