[joshvm]

I've used the BLK 360 before so some comment here. Essentially you scan at various points within the volume of interest, e.g. you walk around, place the scanner, scan, repeat. Each scan takes a few minutes at high angular resolution. Leica provides software called Register (or Cyclone) to match the scans together. Because you generally don't have GPS (the BLK doesn't have a GPS onboar and GPS is anyway much more inaccurate than the scan resolution - metres versus millimetres), the software has to do some kind of feature matching to stitch the scans. You get "links" between adjacent scanning points, and then you do a big optimisation pass to combine the scans.

This scan matching is by far the most difficult and time consuming bit. Probably OP had to manually align the scans as a first pass and then the software takes over using some algorithm like ICP (iterative closest point).

This is still only "internal" (i.e. scans are correct relative to each other, but you don't know where the full scan is) and you'd have to combine with an external reference point to geo-locate in the world. Doesn't really matter for this because you're just viewing the pyramid on its own, and you're not overlaying on a map. If you were, then usually what you have to do is take several ground control point (GCP) that are known with high accuracy and then reference that in the scan. You could geo-reference these using an RTK GPS or something, but it's quite difficult to get world coordinates at the millimetre scale and it rarely matters if you're that precise as long as the scan itself is consistent.

This video from Leica shows the full workflow for a typical use case (scanning a house with indoor and outdoor points). Note the point where they link inside and outside, around 16 mins in https://www.youtube.com/watch?v=AV0LPKowOXU

[loufe]

Awesome, thanks for sharing. We use cyclone for 3D CMS scans of open holes at the mine I work at. Cool to see other use cases. Were you using 3DReshaper before the rebranding?

[bambax]

Complete newbie here, but wouldn't it be possible to affix some marks on the walls to help with the stitching afterwards?

[0_____0]

When working with LIDAR scanning systems (Total systems etc) that generate a point cloud, this is exactly what you'd do. Affix a target or fiducial (a pattern you can apply to a surface that shows up in the scan, either because it's very reflective or because it has a high contrast pattern on it), and use those as reference points to stitch your clouds together.

[MezzoDelCammin]

yeah, this is how things used to be done maybe 10y ago. Spheres (good for 360 symmetry) or checkerboard stickers. Problem is, nobody will probably allow You to put stickers onto the interior of the Great Pyramid.

These days there's a shift towards automatic "stitching" (scan registration) on an accompanying device (tablet or a laptop).

Here's a demo of Trimble X7 (about 3y old product). Full disclosure - I worked on part of this. Not sure how much I can go in detail, but the video shows a pretty good basic demo of how this works:

https://www.youtube.com/watch?v=PApO60lOhlg&ab_channel=Surve...