According to the “Roaming Ralph” sample page in the manual there is a better way of getting the height of the terrain but it is not implemented in the demo. Here is the quote:
Out of curiosity, what is that method? Thanks 
Maybe it means using collisionHandlerFloor for walking on the terrain and collisionHandlerPusher for trees and rocks is a better idea, or maybe it means using visible geometry for collisions is a bad idea.
Its all explained here: discourse.panda3d.org/viewtopic … 18&start=0
using visible geometry for collision is indeed slow and discouraged. extra collision geometry does a lot good. using advanced techniques such as quad and octrees can speed up collisions by several magnitudes depending on your application.
I believe in this case it is using GeoMipTerrain.getheight() method.
the roaming ralph doesnt use geomipterrain. if you use it, getheight() is a fast way to get the elevation under a certain point/node.