1 Mark I Eyeball only has three measurements, tho: High, Really High, and Hey, God! Little help?

Heh. OK, that's my lame attempt at rocket humour. And I haven't even taken any cold medicine!

2 Dang, I thought I invented that device!
After your post about Air Munuvia's maiden voyage I wondered how you could determine how high it went. "Easy," I thought, "just measure the vertical side of the right triangle by looking along it's hypontenuse from a known length of the horizontal side!" (I never got around to writing up a table, though.)
This is as disappointing as the time when I was in K-mart, aged 9, and discovered that my battery-heated socks idea had already been invented.

3 Also, that system is accurate only if the rocket climbs perfectly vertically. It would be a good idea (if you really want an accurate measurement in the case of a competition, say) to have someone else with a perpendicular view to measure the angle from the launchpad to the rocket at apogee.
If the rocket curves toward the tracker then the reading with show that the rocket had reached higher altitude than it actually reached; and it curves away from the tracker then the reading would understate the true altitude.

4 psst... Spork... last paragraph.

5 D'oh! I guess I stopped reading too soon.

6 Easiest way to tell how high a rocket went is to launch it indoors.

WhooshCRUNCH!

"About eight foot six, wouldn't you say?"