Reminds me of the tool we'd use in model rocketry.
The Estes Alti Trak: https://www.amazon.com/dp/B0004HJO9M/?tag=pyrocommunity-20
You stand a known distance from the launch pad, launch, and hold the trigger down. Point the tool at the apex of the trajectory and release the trigger. The indicator on the side will tell you the max height reached. It does the geometry for you.
A big thanks for that item brings back the days of model rocketry way back in late 60's. Could be useful for gauging height of single shot comets, cakes or fan items. For most 1.3 shells look up the extensive article by ken&bonnie kosanke who did research on shell heights, velocity ,drift angles burst diameters and too many others to mention. I have over 6 of there publication books.