For my experience, in GA planes, at aerodromes where obstacle clearance could be a factor, there is rarely authoritative information about the dimensions. For aerodromes/airports which do publish those numbers, there's usually ample space for GA operations at Vy or faster, obstacle clearance performance/technique is rarely necessary.
Where obstacle clearance technique becomes important is at aerodromes (or other places) where there are obstacles, and the dimensions (takeoff distance available and obstacle height are not stated. The airplane manufacturer has provided performance information to fulfill certification requirements, but it's rare that it's exactly those combinations of dimensions, when you really do need to know. If, at the non published dimension aerodrome, you can acquire measurements, that's great, and I have used Google Earth for this purpose. Often, it's simply a judgement, with a conservative go/no go point along the takeoff run.
When I train this, I train the student to simply clear the obstacle with the greatest airspeed, and a lesser clearing altitude. I'd rather see the extra 5 knots of speed crossing the obstacle, than an extra 100 feet over the obstacle. If the speed was not at least Vy crossing the obstacle, the extra 100 feet really did not help you much if it quit. You'd use it up simply getting back the 5 knots you could have had anyway. For the few runways I have used where very tall trees (100 feet) were a certain obstacle (at the very end of a 1500 foot runway), I have disciplined myself to aim at the 2/3 height point of the trees, and accelerate toward that point as though I'm planning to ram the trees, and then smoothly pull up over them in the last few seconds, momentarily trading speed for altitude only as needed. I practice this in my own home runway, as I go out between 60 foot high trees right at the end of my runway. But my very ind neighbour let me cut down the obstructing ones 30 years ago when I purchased the property. I have a good reference for obstacle clearance technique, with lower risk while practicing.
Obstacle clearance takeoffs are sometimes required in smaller runways, and are commonly required for water takeoffs, as it is very common for a lake to be bounded by trees, and perhaps hills. And your takeoff path on a lake is very much less likely to be accompanied by dimensions (hence preplanning with Google Earth in recent years!)