Molemot
All I can say and this involves many aviation regulations too is all is fine until its not fine.
A serious incident especially involving loss of life will mean that the authorities won't care a jot on how you determine that height.
f they can prove that you broke a regulation that is what they will use. You may use the fact that you could not determine the actual height as mitigating circumstances but it would be seen in the same way as me driving a car with a broken speedometer which was not accurate and exceeding a 30mph speed limit.
I would still be guilty of breaking the limit the judge may take into account that I believed the speedo reading was accurate. If my exceeding the limit involved a crash and loss of life of a pedestrian that may influence my sentence
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