Best make sure the area the jumper is traveling is completely flat then, for the running jump, to be able to fairly contrast it with the standing jump.
Last time I checked, a basketball court was about as flat as you can get.
It could still slope, and not be level. That could affect the measurement, if the spot you running jumped from was upslope from the spot you standing jumped at.
Thinking about it, I think they also use the method of measurement they do for both standing and running high jump because it focuses on measuring how far off the ground the person gets. Not on how much reach their arms have. I think that jumping up to smack a hanging object isn’t as accurate in the end, because a person’s reach affects the measurement.
Unless the person’s arms are growing in between trials, I don’t see how this prevents him from measuring his relative jump height with fairly good accuracy. We’re not comparing him to others, after all; he’s only interested in his own results.
:dubious: Where do you play basketball? I’ve never had an issue with the ball rolling away when I put it down, which tells me the floor is generally level enough for our purposes.
Older buildings settle. 
You can’t prevent this. I’m glad you had one to play in that was still level, apparently. The settling problem also makes little “dips” in the court that can accumulate with sweat as well. Slipping hazard. wry (Yes, I played basketball, and have seen the balls gently roll away, and seen the “dips” get sweat in them and be mopped up by a towel.)
Wow, deep breaths folks, take it easy!
I think my posts have been pretty clear. Let me summarise the pertinent points:
- I want to know what method gives the greatest **height ** - standing or running.
- I do not believe there is a sport which demonstrates this conclusively. Of course high jump seems logical but i have mooted that the clear advantage seen by running vs standing stats in this field may be due to the need for horizontal travel to clear the bar. I don’t know if this is true i’m just questioning it.
I didn’t really expect anyone to make any kind of calculations, although i’d wager that it would be possible for those clever enough (consider that a challenge if oyu will). I expected suggestions for answers to come from the world of sport but i had already considered the high jump. What about basketball? Any BB fans know if their favourite player **needs ** a run up to dunk the ball? That would be a more direct comparison as the running would serve no other purpose than to increase height.
BTW - The test contrapuntal suggested is exactly what i tried. In my OP i stated that for me there didn’t seem to be any difference. The fact that this method accounts for reach does not cause any problems. It’s merely a test of one method versus another by the same person with the same reach - i’m not suggesting this become a sport or anything!