If you have to deal with vertical cliffs or rocky walls “high definition orthomosaic” should be a really useful tool to use.
Photogrammetry can do it.
A SfM (Structure from Motion) software processes pictures and measurements to build a 3D model, made up by triangular elements to form a mesh surface.
Actually, before the mesh, it creates a dense point cloud.
Pictures are also used to build a texture that covers the 3d surface as a dress.
A high definition dress!
You can move, orbit and rotate the model in the 3D space, in order to inspect it, as you prefer.
And you can generate and export a high definition image of a specific view.
Well, the software does it for you!
Photos are rectified, in order to get rid of lens distortion, and then stitched together for a really big image file, with lots of details in it.
You can use the orthomosaic to plan rock nailing, where the rock is fractured, it disgregates and falls down, or if you need to extract new material from a rocky wall in a quarry.
It could also be useful for 2D drawing of new structures on the wall, or precisely defining how and where to work on a facade.
Especially if the building is important and architecturally considerable.
This image shows an orthomosaic of a cliff in Riomaggiore, 5 Terre, Italy.
I was assigned for a 3D survey of this area, in order to study how to keep people safe from rock falling.
I shot pictures from a UAV (DJI Phantom 4 Pro), measured high precision GCP (Ground Control Point) with a dual frequency GNSS receiver (Geomax Zenith 20) and mix up everything in Agisoft Metashape Professional.
I was able to deliver some interesting high definition images, like this one, from various angles and points of view, to the engineers that were asked to solve the problem.
Here’s the 3Dmodel uploaded on Sketchfab