You would not plan a road to an area that you have never been to in real life either. You get the lay of the land before even planning the route to take. During exploration i always mark unique features of a path such as poison, tunnels, pathways leading up cliff walls, large open areas great for base building, resources, etc. That way when i plan anything I can reference all my beacons with notes to find out where I should or shouldn't build.
This game requires a great deal of pre-planning to make things efficiently. You can still make roads and factories on the spot without trouble, the only variable is efficiency. As such I have never even considered the need for a height filter, and already think that the scanner is overpowered. I feel that the scanner should work more like the object scanner where you get a general idea of the direction and whether or not its close by. This world map is so rich in content and uniqueness that there is no reason not to explore it.