Contour lines are helpful, but they don't show what is
between the lines. East Central Ohio has some terrain with mini cliffs. Some of these cliffs are only 8 feet high and thus, they won't show up on a topo map. But when you get there on foot, they are an impossible road block unless you employ some way of climbing over it.
I have one access that is near perfect. It follows a deep ravine with side cliffs up a little stream. No deer on either side of the ravine can see a human down in there. The only problem is at the head of the ravine is a 9 foot, undercut waterfall. It's basically a box canyon with no way to continue up the stream. But I built a ladder that's strictly for getting up over the falls. None of these topography features show up on a topo map.
There are a lot of terrain details that don't show on any map.
I know of areas that are basically flat, but streams might have a 10 foot vertical bank of pure mud. These banks are impossible to climb without a rope or ladder.
I have another access route that scales a small cliff (that does not show on a topo or even Google Earth). At 1st glance when standing at the top, or bottom of the cliff, it seems impossible to climb. But there in a little ledge that works it's way across the face of the cliff on an upward angle. It turned out to be a fantastic access route because the cliff basically shields me from being seen by deer that are on top in the woods.
There are a lot of terrain details that don't show on any map.
Here is my ladder in the box canyon on a morning after a sudden freeze that followed a substantial rain. The waterfall was splashing water all over my ladder and freezing.
I definitely had a pucker syndrome when I climber it that morning!