We have been experimenting with using the iphone's 3d sensors (it uses a combination of structured light and lidar for it's 3d sensing) in the lava tubes in Iceland and have found it to be vastly superior to using the disto alone. This is partially due to how strongly magnetic the lava is (magnetic anomalies of 10s of degrees are very common). In addition to the lidar and the structured light sensors, the iPhone uses its magnetic sensors and accelerometers, this helps it create an accurate model but does also cause some issues. While the addition of the accelerometers and 3d sensors do really help, the magnetic anomalies do still sometimes cause us some issues, the models tend to tear and become inaccurate when we encounter those. In tight passages it is also very easy to bump the phone against the floor or ceiling and due to the accelerometers this always messes up the map. To mediate this, we try to keep our scans to no more than 20 minutes at a time when surveying in difficult sections and stitch them together afterwards. This prevents us from having to repeat large and difficult scans, but does add some extra work at the computer.
In addition to giving a much more detailed model of the cave than one would get with the disto the survey also goes much faster. We have easily halved the survey time in addition to removing much of the frustrations of the previous methods using the disto x (although it does introduce some new frustrations of its own). We have not experimented with creating maps in Therion from iphone generated 3d models. None of us has prior experience with working with 3d models so that alone has been a quite steep learning curve with still some way to go, and on top of that we have only limited experience using Therion, so that is another learning curve we have to scale. I have experimented with using Jari Arkko's cave-outliner ( https://github.com/jariarkko/cave-outliner) to generate outlines and cross-sections and used Inkscape to add details. Here is an example of a scan from a survey expedition last summer: https://poly.cam/capture/9A259EC8-3C88-446A-9023-0E589588821C - Can take up to a minute to load, so be patient. https://map.is/base/@419189,311927,z14,0 - Aerial photo of the cave's unique location within the main crater (shared freely online as the whole island is closed to the public and has a *very *strict access control, only allowing a single scientific exploration per year). This year's expedition was recorded and included in a documentary celebrating the islands 60 year anniversary. It is available online here (only available in Icelandic, sadly): https://www.ruv.is/sjonvarp/spila/surtsey/35251/ag5o1h - The cave section starts at 49:30 and the iPhone lidar can be seen in action at about 52:50 Best regards, Þórir Már On Mon, Dec 11, 2023 at 2:08 PM Julian Todd <jul...@goatchurch.org.uk> wrote: > If you can export your file as a las/laz file (or it also takes PolyCam's zip > file of a laz file), > then I have a place where you can preview it using the potree.org software. > https://las.nix.how/ > > Try using the shortcode: c0987 to see a scan that was made underwater using > photogrammetry. > > The potree software converts the pointcloud into streamed data, so it doesn't > matter how > massive your starting scan is as it only loads a limited amount. > > This is used as the starting point for tunnelvr, should you choose to use it > for tracing > > up your scan into a 3D map representation. > > Julian. > > > > On Wed, 29 Nov 2023 at 13:28, Bill Gee <b...@campercaver.net> wrote: > >> Hello everyone - >> >> This is probably more of a general practices question than something >> specific to Therion. Among the group there is likely to be some >> experience with this. I hope at minimum someone can guide me to a place >> for further learning. >> >> A few years ago Apple released a very high-end smartphone which has a >> LIDAR feature (iPhone 12 Pro). There are a few more models now which >> have it. I have heard of some people using this to create cave maps. >> There is much I do not understand. >> >> Has anyone in the group taken the point cloud from an Apple LIDAR scan >> and turned it into a Therion cave map? If so, I am very interested in >> the details of the process. >> >> The biggest issue I see is this: How does the iPhone know where it is? >> There is no GPS in a cave. GPS is not accurate enough even if it did >> work. Inertial navigation also has big problems dealing with a cave >> environment. >> >> There are many other issues, but I think that is the big one. >> >> Thanks! >> >> -- >> =============== >> Bill Gee >> _______________________________________________ >> Therion mailing list >> Therion@speleo.sk >> https://mailman.speleo.sk/listinfo/therion >> >> _______________________________________________ > Therion mailing list > Therion@speleo.sk > https://mailman.speleo.sk/listinfo/therion >
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