cave survey – Caving – Diving

15 August 202315 August 2023

Static Laser Scanner

Whilst my cave surveying efforts to date have been mostly focused around grovelling around in small passages trying to use a Disto and/ or Gopro and lights to capture data to create accurate models via photogrammetry my mind was slowly turning on how to survey bigger chambers, laser scanning is the obvious answer.

Cut through of GB’s Main Chamber created from a compilation of scans

In 2016 I used a Geoslam Zebrevo to survey a few local show caves and other sites, this worked very well however the cost and chance of damage to the device in real caving situations is not something I would like to risk. I had heard that some people had attempted to create a DIY version as the SLAM code was apparently available open source, this triggered lots on internet searches on the subject. I wrote off the Cave-a-tron type system as it wouldn’t easily fit into a dry tube to be dived through sumps to survey passages beyond which is something I wanted to be able to do.

Sadly I didn’t find anything I felt I could build within my skills or cost means that could recreate a SLAM type scanner, however I did find some people had successfully built tripod scanners using fairly simple and off the shelf components. What was even better was that second hand laser units they had used were readily available on Ebay at quite a cheap price relative to the cost of a new unit.

The base laser unit itself was a Velodyne VLP16, a small compact unit that I had used professionally on a few occasions, a short time ago these retailed at around £5000 new but are now in the region of £2500. I snapped up two used ones on Ebay for: $400 and $250 (I’ve since damaged the $400 one).

At this stage I should give massive credit to the originators of this idea who’s designs and softwares have allowed me to realise my own version of their scanners. The first is Jason Bula’s:

https://github.com/jason-bula/velodyne_tls

His scanner and Matlab based code is quite rudimentary but paved the way for another person to further refine and inspire my device, Donny Mott’s:

https://github.com/Rotoslider/TLS_Pie

So to reiterate, I have simple re-arranged components they have used into a form factor which suits my needs and have used their software /code to process the data, nothing massively clever on my part. The result is a compact tripod based scanner that is far cheaper than any commercial offering, I can carry all components myself readily into dry passages or through sumps without external help as the scanner fits in a small pelicase or a small dry tube. I had recently signed up to CREG journal and partway through this process saw an article showing how a Cave-a-tron had been converted to be used on a tripod like the device I was building at the time, however the laser is very primitive compared to a Velodyne unit.

It took quite a few months of trial and error with various components to get data of an accuracy that I was happy with, this was mainly due to the use of a stepper motor with 50:1 ration planetary gearbox. It didn’t quite rotate at a consistent speed meaning that when overlaying two scans from the same location features were not in the same place as they should have been. I replaced it with a different stepper motor with a 30: 1 harmonic drive and finally was happy with the results. Many other things were tried or swapped in this time before the gearbox was identified as the cause such as power supplies, wiring looms and Arduinos so it wasn’t as straight forward as it sounds.

The main components are:

Velodyne VLP16: Laser scanner mounter vertically on a slowly rotating frame

Raspery Pi 4: Logging of Ethernet data from VLP16 using code written by Donny

Arduino: 3 x push button controls of the stepper motor and logging commands to the Pi4

Stepper motor and Harmonic drive: Provides the smooth slow rotation

Lipo battery: Power for all components

Various other DC-DC converters, switches, wires etc necessary to interface the components.

The scanner is mounted to a tribrach bolted onto a tripod and leveled, either button can be pressed to initiated a scan. The scanner then starts to slowly rotate and the Raspberry Pi4 logs the data to a file, no results are visible in realtime. Once the scan has finished the tripod is moved to the next location, leveled again and another scan initiated. In this manner progress through cave passage can be made, usually 7-10 m at a time between scans but this depends on the nature of the passage. Once back at home the raw scans are turned into point cloud files by Donny’s excellent piece of software and can be aligned together using cloud compare’s manual tools initially then its fine align tools. Below is a video taken by Duncan Price of the scanner in use in Wookey Hole.

Time lapse of use in Wookey Hole, video by D Price

Scans have so far been undertake in:

Badger Hole

Wookey Hole Chamber 20/ passages beyond

Wookey Hole Chamber 22

GB cavern (all of the large main passages and Great Chamber)

Numerous tests in my garden

Interested in how accurate my scanner and methods were I surveyed a close loop around a house, the loop was 76 m in length and contained 9 scanner locations, the misclosure was less than 20cm in XYZ between the same point visible in both the first and last scans.

This I believe to be far more accurate than what can be achieved with a Disto in a cave though it lacks alignment to either magnetic or true north so its accuracy is only in a relative sense. Alignment to a disto based centre survey could be used matching up common reference points in Cloudcompare to align the laser scanner data.

A commercial laser scanner would achieve accuracy far greater than this but the cost would be 15-100x more along with a large sense of paranoia with regard to damaging the unit in the cave environment. The Velodyne laser doesn’t log point colour but is does log intensity so this can be interesting to colour the resulting point clouds by.

The below video shows the data data I collected and aligned from GB cavern, Donny made the fly through after I sent him the data to show him what I had been doing with his ideas and softwares, it starts at the mud run in at the top of the major passage and goes down to the choke just below ladder dig.

At this point I feel I have succeeded in my goals, I have a relatively cheap laser scanner than I can take nearly anywhere (whether I want to is another matter, eg transporting through Daren Entrance crawl..) that produces results accurate to a few centimeters and can scan large chambers or passages with ease, now it is a case of working through suitable sites and producing laser scans of places that otherwise might never be scanned unless someone invested a lot of time or man power or money into carrying in commercially available scanner.

2 May 2023

Ravens Well Update

Well its been a little longer than I anticipated updating this page with what I have been working on but rest assured this isn’t due to a lack of activity more a lack of internet at home.

Numerous projects have been going on both on the surface and underground but I thought I would start with some updated data from Ravens Well. For Christmas I treated myself to a small drone (the DJI Mini2) mainly so I could add some surface features to the underground surveys I have been working on though flying it around aimlessly is equally fun !

The learning curve I found to be very easy and by lunch on Christmas day I had produced a model of my house. After a bit more practice and experimentation I was ready to capture the images required to create a surface model of the area above Ravens Well around the three lamps junction of Bristol, ever curious each time I walk/ cycle/ drive over the top as to where the tunnels are exactly beneath this would provide the answer more accurately than just overlaying the underground model/ survey roughly in Google Earth as the Axbridge Caving Group have done.

Ravens well and surface model of the three lamps junction

The flight took about 20 minutes well within the drones ability and Metashape processed the images very efficiently. I used RTK GPS to measure the positions of some prominent features on the ground mainly road marking which were clear and well defined in the point cloud. These were then matched up in CloudCompare resulting in a reasonably accurate surface model of the area. I once again scrambled down to the entrance to the tunnels and to my surprise found that I had fixed RTK status next to the entrance so I marked a temporary point and quickly surveyed from the GPS point to a point marked inside so that the drone data and underground data could be tied to the same reference and overlaid.

Surface point being measured with RTK GPS

Same point in model with tunnels visible underneath

Overall a successful addition to projects, easy to do and gives a better understanding of the relationship between above and underground features.

Three lamps Junction area with tunnel underneath (long shadows from surface features caused by low winter sun)

11 August 2022

Underwater DistoX2 Housing

I will start by saying that this idea has been copied from other cavers/ divers, this isn’t the the first time someone has wanted to use a Distox2 underwater. My reason for wanting a waterproof Distox2 is allow me to use the same methodology for underwater photogrammetry geo-referencing that I use for above water photogrammetry geo-referencing to preserve accuracy through sumps. Lasers do have limitations underwater, light is attenuated by water quite readily especially red light or red lasers. so the range is going to be very limited even in very clear waters.

The main body of the housing is made from Acetal, a small cut out sealed with an o ring allows the laser to emit and receive through the front of the box and is covered by 5 mm thick perspex. The lid is 12 mm thick polycarbonate and houses two brass buttons sealed with o rings to actuate the on/ off buttons. The springs have been taken from a Gopro housing and are the most ferrous part, making the bearing swing by 0.2° when they are swept close to the Distox2, all screws are brass. A standoff is fitted to the rear to extend the rear reference point to make it easier to align to the survey station. The gland sticking out the side doesn’t have a function other than to seal the hole present in the side ( the boxes previous life was a waterproof box for an Arduino Mega).

Due to the difference in refractive index of water and air the distance readings taken underwater are no longer correct when compared to the same measurements taken in air. The refractive index of air is around 1.00 and approximately 1.33 in the water I would be using the device in.

To prove this I made a test in my bath, I put two pencil marks at either ends of my bath, with the Distox2 in the housing I made a measurement with the marks and device underwater then again with the water drained, I also measured with a tape measure for a sanity check.

The tape read 1.415 m, the dry Distox2 in the box read 1.31 m and the wet shot read 1.70 m.

The distance from the rear of the disto to the reference extension stick needs to be added which is an extra distance of 0.109 m, this added to 1.31 m gives 1.419 m which is very close to the taped measurement.

Converting the underwater shots distance requires the offset from the front of the device to the rear to be subtracted first as this is a fixed offset added by the Disto and doesn’t need to be scaled from water to air. There is also around 0.02 m of air in front of the disto before the laser passes through the housing lense and into the water and this doesn’t need to be scaled either, i’m purposefully ignoring the 5 mm of perspex as this is very small compared to the distance of the shots being taken and probably only accounts for a few millimeters of difference.

So starting with the wet shot distance of 1.70 m we need to subtract 0.134 m which is the length of the disto plus the air gap in front. This gives 1.566 m, which we need to scale by the refractive index of water 1.33, which gives 1.177 m. To this we need to add the length of the disto plus air gap and the extension distance so 1.177 + 0.134 + 0.109 + 1.420 m which is very close to the taped distance and the dry measured distance – Result !

Cat testing

The distoX2 manual available here:

Click to access DistoX2_UserManual.pdf

It states that the wavelength of the laser is 635 nm, using this calculator here we can confirm the refractive index of water is around 1.33xx.

https://www.staff.tugraz.at/manfred.kriechbaum/xitami/java/H2Orindex.html

The next phase is some pressure/ wet testing of the housing without the Disto installed in case it leaks then I can begin to put it into use, sump 9 in Porth Yr Ogof is the first place I have in mind for it so that data collected in Parker Series can be accurately aligned to the rest of the cave.

9 July 20229 July 2022

Daren Entrance Crawl (again…and again … and again…)

Last year I experimented with some photogrammetry in the confines of the Daren Cilau entrance crawl, the section known as the vice to be more specific, details can be found here:

The Vice

Spurred on by the success in this short bit of passage I convinced myself that it would be a worthwhile project to try and accurately model the entire crawl from the surface to the final rescue box. One could simply video the entire crawl in single trip and use the video to produce a model but it is important to me to make this model accurate and to do this it needs to be surveyed so that the resulting model and can aligned to the survey data. For assessment of accuracy I surveyed both in and out so the loop closure could be examined and any poor data identified and sorted. To make this task more manageable I have broken the cave up into sections between the rescue boxes, these also make handy survey markers that aren’t likely to change location in between trips.

To date I have completed three trips; a trip consists of caving to the rescue box at the far end of the section with a small bag, surveying out from the box to the previous one then surveying back in. Caving slowly out with the Gopro and light trying to get steady footage before turning at the previous box and filming back in to the starting point. I then pack up the gear and cave back out. This involves lots of awkward caving for those familiar with the cave.

The first two of the trips have been successful and a decent model has been created from the surface (box 0) to box 2. On the third trip I found that my Gopro had been switched on prematurely and battery warning was already on before I started but this wasn’t discovered until after complementing the survey so I had a rather rushed trip filming back from box 3 to box 2 before the battery ran out. After some failed attempts at saving the data from the third trip this means I will have to repeat it as I was moving too fast for the image alignment to be successful.

Plan view of disto data from entrance (B0) to box 3 (B3) coloured by section/ date surveyed.

The distances between boxes is as follows:

Box 0 to Box 1: 79 m

Box 1 to Box 2: 41 m

Box 2 to Box 3: 51 m

Pictures, model and videos to follow……………..

19 June 202225 July 2022

Ravens Well Part 3

Its has taken some time (a bit longer then planned) but i’m pleased to say that the entirety of Ravens Well has been surveyed and photographed resulting in a complete and accurate (to the disto data) model. The same techniques and equipment that were previously mentioned have been used, some sections proved tricky for the software to understand so I have introduced the coded Metashape markers to provide visual and spatial reference, this seems to have solved the issues in certain sections of passages where the alignment was struggling.

There are some ferrous areas inside as the disto data shows some larger than expected loop closures in certain areas despite careful practice. Metal girders are visible in the far downstream area which is the bit which shows the greatest variation when overlaying my data with the previous survey performed by Axbridge Caving Group.

I’m working on a video walk through of the whole site like the previous version so I will upload this when its complete, here is a quick video overview for now, below is low resolution model uploaded to Sketchfab which you can explore with your mouse/ phone.

Video Overview of Model

Low resolution Sketchfab upload (Due to free account limits)

28 November 2021

Downwards at Rickford

A few friends have been working at Rickford Rising removing large boulders and making progress downwards from where the previous protagonist left off some years ago. I have always fancied a dive here but had never got round to it for various reasons. It usually has good visibility so I thought I would attempt to create an accurate photogrammetry model of the site as a snap shot of progress at this point in time, and hope to go back and update the model as progress towards the Burrington Master Cave is made !

A video has been put together by the digging team and gives a rough overview of the site:

I made four short dives on my visit, facing head first slowly filming the descent from surface to dig face allowing sufficient time for the visibility to clear each time and a survey dive (after having planted the yellow builders square on the first dive).

The builders square was used to provide a scale reference (the lipped edge is 12″ or 0.31m long) and also to provide a fixed straight edge along which I could repeatedly align the edge of my survey box with to make foresights and backsights against to allow the model to be orientated correctly. Accurate depth of the square was also measured, 6.8 m to the yellow surface on the day but this will vary with flow and water level effects.

End of the dig and planted builders square (krab is ali)

I have setup the survey box so that it logs data continuously, this allows the diver to retreat whilst measurements are taken minimising any magnetic effects of steel cylinders or other dive gear, this is apparent in the good agreement between foresights and backsights taken, they are no worse than what I have measured on land away from ferrous materials. The upper part of the dig is festooned with scaffold and other metal things.

The survey data was input to Survex and corrected for local magnetic deviation, a resulting bearing of 161° to was calculated for the lipped edge of the plastic square.

The model was processed without issue and was manually scaled, rotated aligned and translated with the survey data measured and the entrance location provided by the cave registry in CloudCompare.

The video from one of the dives can be seen here, attempting to slowly film the waters surface from underneath, down the rift to the current dig face.

A flythrough of the model is available to view below:

18 November 202125 July 2022

More Porth….

The image above shows progress so far, colour coded by area

Over the summer months this year (2021) I continued to visit, survey and video various parts of the cave upstream of Upper Cave Water Chamber. The results are very pleasing because not only is the level of detail being captured far in excess of any survey that has been conducted before (at this site) but this detailed data (the models produced by photogrammetry) is also matching well with the Distox2 data which gives real world scale and orientation meaning its not just pretty pictures which I prefer to avoid.

This area of the cave lends itself very well to my process as each section is short and clearly divided by short sumps giving nice workable areas to focus on. The below image shows a comparison with the UBSS survey in plan view.

Plan view, blue line where visible is the DistoX2 centreline data

Side view, blue line where visible is the DistoX2 centreline data

UCWC looking downstream from Sump 8 (textured model)

Cobley crawl looking downstream into Sump 8 (textured model)

Sump 9 looking upstream (textured model)

Where to go next ? I would like to improve the alignment of Sump 9 relative to the rest of the model as so far this has just been best fitted to the other data and I would prefer to link it directly. After this then adding the passages in Parker Series is the next logical step but perhaps this will have to wait until next summer.

I have uploaded the models of the three dry sections to Sketchfab, its low resolution due to the limits on the free account.

Upstream Porth Yr Ogof by cave-dive-make on Sketchfab

13 August 202114 August 2021

The Vice

So far my attempts at underground photogrammetry have been limited to easy places where walking steadily through a passage poses little to no issue, this where caves are involved is somewhat limiting due to the nature of cave passage formation.

I set myself the challenge of attempting to model something smaller and less easily walkable than what I have done so far to see how collecting the video might be and how well the software would cope with what will likely be non ideal footage for reconstruction.

The entrance passage to Daren Cilau struck me as a good place to try, more particularly the section known as the Vice; A narrow section in which cavers must turn onto one side and keep their bodies high to prevent being jammed into the narrow trench in the floor. It doesn’t pose a particular difficulty to myself in terms of the passage vs my body size and fairly large people can get themselves through but I thought it would make an interesting experiment, the main issue being capturing reasonable video with one hand whilst negotiating the section of cave. It is an iconic cave in British Caving and probably has never been measured before in such detail.

With the above goals in mind I set off one day over to Wales, my plan was to cave the short distance into to The Vice, mark some (min of 4) stations on some prominent features before, through and after The Vice, survey these stations with a distoX2, then cave through this small section a few times whilst trying to take steady video. Using the marked stations the resultant model could then be scaled and aligned correctly. These stations were marked with Tippex which was carefully removed after use.

Source video of one of the outwards trips

A single dive torch was used attached to my Gopro on a cheap ebay selfie stick to keep weight and bulk down.

In practice this went fairly smoothly, the Vice was passed a number of times:
In: Marking stations
Out: Survey with Distox2
In and out: filming
In and out: filming again
In and out: removing Tippex stations

On arriving home I set about processing the images and compiling the survey data. It has become my normal practice to film both directions into and out of a passage, if the alignment is to be considered accurate then both in and out passes should match up (plus any additional passes). This is closing the loop which allows relative accuracy to be assessed and also gives a different perspective on features if its successful.

Separate models for each in and out pass were created first, unfortunately each one giving a slightly different representation of the passage when attempts at aligning them in Cloud Compare were made. I then made a model combining both a single in and out set of images, this was successful in that there only appeared to be a single cave passage which showed that the software was able to combine both sets of images semi correctly. However when this point cloud was matched with the survey data although a low RMS (0.05 m)value was reported the survey data appeared to shoot through the walls of the cave which I know not to be true. I then made a new attempt using all in and all out passes and matched the reference points with the survey data again, this time I got a low RMS (0.03 m) value and the survey data appeared as it should within the bounds of the walls, a good result which I am happy with. This goes to show the importance of some quality control and verification against other sources of data. The images below detail these results.

Single inward pass fitted to survey data

The above image shows the model created from a single inward set of images, Metashape reported all images were aligned and after 7 parameter transformation to the survey points in Cloud Compare a low RMS value of around 0.05 m was reported, however on inspection the survey data (blue line) goes through the walls so something isn’t right. The deviation occurs through the narrowest section where steady filming was most difficult. The image below is the result of the 7 param. transformation.

7 parameter shift results for the single inward model

The below images show the same process as above but using the model derived from a combination of all 4 in and out passes.

All in and out passes fitted to survey data (the roof cut off to allow the data to be seen)

The results for the 7 parameter shift can be seen below:

I am very happy with the results of this, not only has a model of the cave been constructed but it also appears accurate when aligned to distox2 data. The model plus a few extras to aid with scale have been uploaded to Sketchfab here:

‘The Vice’ Ogof Daren Cilau by cave-dive-make on Sketchfab

What I would like to do is attempt to model the entire entrance crawl in this manner…. it might take a while but watch this space !

14 January 202115 January 2021

Lock Down Projects

Well here we are again, in the throws of another lock down. Travel from your local area is frowned upon, all venues (apart from the sea) are closed for diving so to keep stimulated both physically and mentally I decided to experiment with some underground (local) photogrammetry.

My experience of photogrammetry is limited to mostly following others around underwater whilst they photograph things, a few work projects and some failed underwater attempts in a cave (perhaps a separate post on this later).

For anyone thinking of taking it up I have had very good results with mobile phone cameras, Gopro’s and cheap lights, the process is very simple to perform on a computer so I would encourage people to have a go, the software can be trialed for free so expensive equipment is not necessary.

So back to the lockdown; fortunately I have a site I can access within walking distance of my house in which I can experiment, it is an old water conduit known as ‘Raven’s Well’

Armed with a set of cheap waders from Ebay (its waist deep in some places), a Gopro hero 3+black and two cheap video lights I set off to capture some photos to see how well I could model a part of the site.

I set the Gopro to take a still image every 0.5 seconds, put the lights on full and set off walking slowly around the passages near the entrance with the camera pointing forwards. Care at turns was taken to ensure that lots of overlap was achieved. There is a loop that can be traversed so I walked around to see if the software was able to accurately ‘close the loop’ a fundamental part of survey data assessment.

I went round the loop twice in an anti clock wise direction before heading downstream to the low section before returning to the loop and completing the loop again twice in a clockwise direction, this amounted to 1237 photos, just over ten minutes of photo capture. I have collated them into a short video so the quality and coverage can be seen.

Source Images

This amounted to just over 4 GB of data, the details can be seen be below for the Jpeg images for the photographically minded.

Images can be harvested from video but they lack the metadata that comes from still images so I find this approach easier provided you take enough images first time around, with video you can extract more frames without revisiting the site if required.

Photogrammetry is a computer intensive exercise so before I pressed the ‘Go’ button on the whole set of images I tested a single loops worth to see if what I had captured was going to be worth the wait for processing, this took about two hours to go from raw images to dense cloud, I was happy with the result, it failed to close the loop but had modeled the shape and course of the passages very well, see the below image.

The above image is a plan view of the dense point cloud created from one walk round the loop. The areas circled in red are the same physical areas and should join up however at the area highlighted with a blue line (the first corner) it has failed to adjust for the camera heading change properly which can be seen by the ghost walls, if this piece is manually cut and swung round it allows the areas in red to overlap. I was encouraged enough by this to select all the images and pressed the ‘go button’. After all I had 3 more traverses of the loop and hopefully the addition of more images would help it close properly.

This was a much longer process, which took around two days (Macbook Pro running Windows 7, 64bit, 16 Gb Ram, i7 2.9 Ghz). Waking up to a silent laptop (the fans goes into over drive when its processing) on the second morning I was pleased to see all images had aligned and it had finished so I loaded the dense cloud and started to inspect it. I was very happy with the results, the loop had closed and the passages appeared as they should. The image alignment was run on ‘Medium’ and the Dense Cloud was set to ‘Low’. More detail could be processed at the expense of processing time but for me this is good enough.

The first job once the initial overview had been completed was ‘cleaning’ the water out of the floor, most of the areas have a wet floor and its unsurprising that it struggles to model a constantly moving, colour changing body of water so these points were manually selected and removed. Once this had been completed the mesh and texture were computed, taking just a few hours. Below are some selected views from inside the model, I am working on some sort of video or fly through to be posted when available.

Looking towards entrance down brick roofed tunnel

Future work will involve covering the rest of the site and geo-referencing the data to the real world as an arbitrary scale and alignment is applied straight from the software.

26 December 202026 December 2020

Underwater Testing

Sometimes its one of those days when nothing goes your way (of course you are still happy and healthy but the given goals for the day are unachievable), I set out last week with the aim of thoroughly testing the survey box underwater and having a good ride around on my scooter before the onslaught of a dry Christmas.

A short line course was laid underwater and surveyed by a friend with a Mnemo survey device (part of which is the inspiration for my own creation). I began taking foresights and backsights with my box (having added two line clips to allow hands free alignment with the line. Unfortunately on logging shot number 13 (unlucky for some) the display somehow went back to front then froze and refused to continue to work. I had planned to survey the course three times for further device assessment and comparison against the Mnemo but was unable to complete one entire loop.

Survey box line clip and count down modifications.

We were planning a dive of around 2 hrs, a bit of surveying then some scooter fun, having had to abandon my surveying after 20 minutes I decided to take my scooter for a run wanting to assess how much battery life I might have available in its top speed. Clipping off the tow cord I took off but every few seconds the motor cut out then restarted, making the already distinctive Aquazepp sound even worse. I quickly decided that it was inconvenient but didn’t seem to be doing any harm so stopped next to a known landmark then took off for a lap on the turning of a fresh minute of the dive time on my computer.

It took 20 minutes to complete a lap which is known to be about 1100 m at the depth is was taken at. Arriving back at the line course I decided that I was against any further scootering but would surface quickly, reboot the survey box then head back to the line course to complete my goals.

Surfacing went fine, kept kit on, isolated my oxygen supply, quick minute with a handy screw driver to open the power port on the survey, rebooted and re-calibrated it, all fine so closed it back up. Mask on, oxygen back on… PSSSSSSSSSSSSSSSsss the hose had popped off of my Kiss MAV 🙁

Kiss MAV thread failure

I thought it might have just come undone to start with but after a few tries it was clear the threads had gone and that was the end of the rebreather diving for the day, I had left my scooter underwater so went back in on my open circuit bailout to retrieve it.

To top the day off there was a power cut so no hot drinks or food were available 🙁

The list of annoyances goes as:

i) Frozen survey box display and Arduino after 13 shots (hopefully a random occurrence)

ii) Scooter not running smoothly (investigation ongoing)

iii) Kiss valve thread failure (its quite old and known to happen so…)

On arriving home and sorting out gear I was still able to download the 13 shots I had taken before the device froze, after the addition of the line clips I’m happy with the few foresight and backsights I was able to take, the first belay was metal as well as one in the middle so those are expected to be bad but the rest agree quite well I think, further testing to be done to confirm.

So taking away some positives…. I was able to complete a ‘fast lap’ on the scooter and after charging the batteries have discovered that 24 minutes of use used 2500 mAh from each battery giving about 160 minutes of burn time at top speed. The data I was able to collect with the box is encouraging and it seems to be able to record foresights and backsights to within a few degrees away from large metal objects. The Kiss valve failed on the surface not underwater. Further testing planned….