Hello, I have a question about the usage of depth-to-Diameter (d/D) ratios to calculate the depth of a crater using its diameter due to the lack of a good depth angle (Examples here:
1 and
2; it's manhwa, but that's just because I'm most familiar with manhwa, but I've seen blogs from other mediums use this ratio too). I'm also guilty of using it too for one of my calculations, so willing to change it. Originally, the argument about its usage was talked about on this thread
here, but as I'm thinking about it, due to its rapid usage in a bunch of other calculations, I thought it could be a possible staff discussion due to its usage in many other manga/manhwa calculations.
My argument (TLDR) was against its usage due to: The d/D ratio of 0.11, 0.17, 0.25, etc., is borrowed from meteor impact studies where even under controlled conditions the ratio varies widely from 0.08 to 0.215 with no confident trend, as acknowledged by both these two articles:
Hoover et al. and
Stopar et al (Full PDF locked in a paywall but main points can still be read). Neither paper can identify which factors — velocity, target properties, impactor properties, degradation — dominate the final ratio, making it unreliable as a fixed value. Especially applying it to a way below 40m punch crater, where no data exists, and the trend suggests the ratio would be even lower, means many calculations likely overestimate depth and therefore energy. I believe it shouldn't be used at all due to the different creating conditions (high velocity meteorite impacts), and especially ratios like 0.17 and above shouldn't be used for craters with diameters below 40 meters. Seeing it be used on like 1-5 meter craters and using those ratios to say it’s 0.17-0.85 meters deep when they genuinely don’t even look a cm or 2 deep often inflates the calculations (I can give some examples I’ve seen but don’t want to seem like I’m targeting people).
The opposing argument (feel like it should be brought up) TLDR: The crater visually resembles a simple bowl-shaped crater, and since lunar simple crater research documents d/D ratios in the 0.11–0.17 range, applying 0.17 is a reasonable approximation regardless of formation mechanism and diameter size. The speed difference between a meteor and a punch is a minor factor that doesn't significantly change the final energy values and geometric outcome of a simple crater. Since the ratio doesn't change dramatically even across large diameter ranges (a sample size of
930 (the Stopar one I sent above)), a 3.77× size difference won't meaningfully shift it either.
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