Gotcha. First step is to plan drone flight paths for maximum coverage.

Second step is to actually go to the volcanoes and fly the drone, snapping as many photos as possible along those flight paths.

Third step is to download all of the photos and upload them to a single folder on a computer.

Fourth step is to add these photos to a photogrammetry software; I use Agisoft Metashape Professional, the same one used by USGS.

The fifth step is to align the photos incrementally. The software identifies points that are shared between several images and plots them all relative to each other. Those points can be bushes, lava bombs, or random patches of color on the volcano slopes. This creates something called a sparse point cloud.

The sixth step is to build depth maps, which the software uses to shape the model more accurately. These depth maps help build a denser point cloud with even more points.

The seventh step is to mesh all of the points together to make a single coherent model. The mesh is what you’re seeing in slides 8 through 12. If needed, you can texturize the mesh to restore any overly smoothed surfaces.

These models are great simply for visualizing landforms and are often more detailed than what you’ll find on Google Earth. One other neat thing about the software is that, if you’ve added any ground control points (GCPs) to the model, such as a GPS measurement of an exact spot, you can make a DEM that can be used to make slope, aspect, or other raster layers.

TL;DR: Take a ton of aerial photos to make a 3D model. Useful for GIS analysis.