<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">Hi guys,<div><br></div><div>You can also view a 3D cave from a photogrammetric survey with caveview on Karst3D. Here is the link to the cave:<div><div><a href="https://data.oreme.org/karst3d/karst3d_map#selected_layer=karst3d_station&selected_station=61">https://data.oreme.org/karst3d/karst3d_map#selected_layer=karst3d_station&selected_station=61</a><br></div><div><br></div><div>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.</div><div><br></div><div>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 </div><div><br></div><div>Cheers,</div><div>Phil</div><div><br></div><div><br></div><div><br><blockquote type="cite"><div>On Nov 29, 2023, at 19:45, Martin Budaj <m.budaj@gmail.com> wrote:</div><br class="Apple-interchange-newline"><div><div>On Wed, Nov 29, 2023 at 4:47 PM Bill Gee <bgee@campercaver.net> wrote:<br><br><blockquote type="cite">Looking at the sample files, it looks like he extracts some images from<br>the point cloud. One of them is an overhead view and others are cross<br>sections and profiles. He then uses these JPG images as the drawing<br>background to produce a traditional cave map. The LiDAR scan<br>essentially replaces the in-cave sketching. I suspect there is some<br>custom software to extract the images from the point cloud.<br></blockquote><br>Indeed, the scans (combined with videogrammetry as in iPhone or iPad)<br>preserve a lot of details and can be used to draw 2D maps. However,<br>they can't completely replace the sketches or notes, as there is much<br>information that can't be captured in the scans (air droughts, lake<br>bottom etc.)<br><br><blockquote type="cite">I remember some years ago hearing about some mapping projects where the<br>survey stations were marked with small balls in a specific color. The<br>processing software recognized that color and provided a way to connect<br>those points to known x,y,z locations - a centerline. It was<br>fantastically expensive in both money and computer resources.<br><br>In a way, we do sort of the same thing with Therion. The centerline<br>data is processed to produce a set of x,y,z coordinates. The survey<br>stations are flagged in that data set. Then when the sketch is drawn<br>out, we insert points of type "survey station" which are also flagged.<br>The sketch can be considered as a sort of two dimensional point cloud.<br>Therion knows how to match up the survey station points in the sketch<br>with the survey stations in the x,y,z coordinate set. From there it can<br>morph everything around.<br></blockquote><br>This is exactly the plan how to implement it in Therion, when time permits:<br><br>1) you scan a fragment of a cave (a 3D scrap) with some survey<br>stations visually marked<br>2) you assign station names as used in Therion centreline to local 3D<br>coordinates in the 3D scrap<br>3) Therion warps the 3D scrap and aligns it with the centreline<br>4) ideally, Therion smoothly joins adjacent 3D scraps<br><br>The result would be a 3D model which could combine the walls captured<br>from scans with those generated from the 2D scraps and LRUD data. This<br>way you could progressively improve the 3D model as your LiDAR<br>scanning progresses.<br><br>There is a preliminary issue for this here:<br>https://github.com/therion/therion/issues/475<br><br>Martin<br><br>P.S. Here is a 50-metres dig scanned by an Apple LiDAR in around 30<br>minutes: https://photos.app.goo.gl/Cvs8mej2RCqpGoj9A<br>_______________________________________________<br>Therion mailing list<br>Therion@speleo.sk<br>https://mailman.speleo.sk/listinfo/therion<br></div></div></blockquote></div><br></div></div></body></html>