Hi guys, You can also view a 3D cave from a photogrammetric survey with caveview on Karst3D. Here is the link to the cave: https://data.oreme.org/karst3d/karst3d_map#selected_layer=karst3d_station&selected_station=61
If you visualize the 3D lox file, this is a therion survey and if you visualize the 3D file (PLY), this is downgraded photogrammetric survey. You can easily project on a map the 3D point cloud and draw a map on it but in this case you have to work with a GIS software. The best would definitely be to have a code computing virtual survey stations to input it in therion, it could also be based on the trajectory of the camera used for the 3D photogrammetric model Cheers, Phil > On Nov 29, 2023, at 19:45, Martin Budaj <m.bu...@gmail.com> wrote: > > On Wed, Nov 29, 2023 at 4:47 PM Bill Gee <b...@campercaver.net> wrote: > >> Looking at the sample files, it looks like he extracts some images from >> the point cloud. One of them is an overhead view and others are cross >> sections and profiles. He then uses these JPG images as the drawing >> background to produce a traditional cave map. The LiDAR scan >> essentially replaces the in-cave sketching. I suspect there is some >> custom software to extract the images from the point cloud. > > Indeed, the scans (combined with videogrammetry as in iPhone or iPad) > preserve a lot of details and can be used to draw 2D maps. However, > they can't completely replace the sketches or notes, as there is much > information that can't be captured in the scans (air droughts, lake > bottom etc.) > >> I remember some years ago hearing about some mapping projects where the >> survey stations were marked with small balls in a specific color. The >> processing software recognized that color and provided a way to connect >> those points to known x,y,z locations - a centerline. It was >> fantastically expensive in both money and computer resources. >> >> In a way, we do sort of the same thing with Therion. The centerline >> data is processed to produce a set of x,y,z coordinates. The survey >> stations are flagged in that data set. Then when the sketch is drawn >> out, we insert points of type "survey station" which are also flagged. >> The sketch can be considered as a sort of two dimensional point cloud. >> Therion knows how to match up the survey station points in the sketch >> with the survey stations in the x,y,z coordinate set. From there it can >> morph everything around. > > This is exactly the plan how to implement it in Therion, when time permits: > > 1) you scan a fragment of a cave (a 3D scrap) with some survey > stations visually marked > 2) you assign station names as used in Therion centreline to local 3D > coordinates in the 3D scrap > 3) Therion warps the 3D scrap and aligns it with the centreline > 4) ideally, Therion smoothly joins adjacent 3D scraps > > The result would be a 3D model which could combine the walls captured > from scans with those generated from the 2D scraps and LRUD data. This > way you could progressively improve the 3D model as your LiDAR > scanning progresses. > > There is a preliminary issue for this here: > https://github.com/therion/therion/issues/475 > > Martin > > P.S. Here is a 50-metres dig scanned by an Apple LiDAR in around 30 > minutes: https://photos.app.goo.gl/Cvs8mej2RCqpGoj9A > _______________________________________________ > Therion mailing list > Therion@speleo.sk > https://mailman.speleo.sk/listinfo/therion
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