Zero Memory cost
The topography is built on the fly. No extra memory than the raw elevation data is required.
Constant traversal time
The traversal time of the topography doesn't depend on the number of data nodes. It only depends on the ray length and on the topography features.
Optimised for Monte-Carlo
Only local topography data are used at each Monte-Carlo step. This allows for fast steps with an average cpu cost of only O(500) instructions, i.e. a few hundreds ns per step.