Aerial photogrammetry and ski areas

Knowing well where an avalanche could start is very important for designing of barriers.

The distance between alignments is a crucial parameter for a good snow-retention action.
If barriers are too far away there's the risk that snow could move and damage them.
If they're too close and you're gonna waste money protecting an area.

A good topographic basis helps you in the project and in the right estimation of the amount of barriers.

You're gonna check everything durineg the "tracing phase", but if the project is not propoerly based on a good ground data there's the chance you had decided for too many or too few barriers.

Aerial photogrammetry works well here because there's almost no high vegetation at all.
Wood racks (like those in this pic) are usually put in place where the forest is supposed to grow again.
There may be few scattered trees to deal with in the processing, but it won't be a huge problem.

Metal structures, on the other hand, usually end up in 'clean' areas and structure from motion software will do a really good job in modeling them.