Here is a simple high score method:
I just made some simple calculations on the position of the gbm every tick, using Sprite3.Top as ground coordinate, and offsetting for the centered hotspot of the gbm. It's not exact if the sprite is sideways, but it would likely be overkill to nitpick that.
The black bars were adjusted to be centered 500 pixels from top of the ground sprite, and each other, and that represents 10m, hence the '/ 50' in the arithmetic.
The highest point is determined by comparison between two variables. A fairly common method that one might employ in such a situation.