Lidar Mapping support rescue of 13 Thai boys trapped in Thamluang cav, Chiangrai, Thailand

[Phisan Santitamnont]

I would like to ask you about experiences of applying Lidar Mapping support rescue of  

man trapped in a cave. In the case of Thamluang cave, Chiangrai, Thailand

If we could have a dense of lidar 15 to 20 pt per square meter 

We could produce following products for following purposes:-

1. Generate bare-earth DTM of the mountain superimpose with 3D cave map.

   Even the 3D cave map most is sketch from compass, tape and inclinometer.

   It will provide value information for thickness of cave wall purposed drilling \

   if necessary

2. Canopy Height Mode generation will show contour and slope.

    Drilling engineer need badly good location for drill operation.

    I suppose we could have 'minus' canopy that will imply the search of cavities.

   Thai rescue team is searching for cavities that might connect to

   the main cave.  

   Any of you have ever experienced use this kind of application.

3. Thamluang cape is in fact the pathway of underground river system.

   So hydrologist need to know precise watersheds  and underground water system

   to dewatering the cave. 

If you any image support this ideas please help me.

At the moment we got interest from airborne lidar companies to support these work

but sadly the government see no benefits from this operations.

Thank you for attention.

Martin please help me with examples and you experiences.

Phisan Santitamnont

Chulalongkorn University

[David Pont]

Hi Phisan,

  Great idea. Airborne scanning would provide a good DTM, perhaps at 1 ground point per m2 ? (pulses per m2 needed will depend on vegetation). Existing terrain data may even be adequate for a start? An accurate map of the cave interior is the missing piece. I suggest looking at the ZEB1 hand-held scanner for mapping the inside of the cave – it was initially designed for mapping underground mines. You would likely need some control points, the existing compass, tape, inclinometer data could provide this, perhaps with some additional surveying to verify and improve accuracy. The water locks will not be able to be mapped, causing breaks and alignment issues, this will be a challenge. The device is not too expensive, and we have found it very easy to use.

An accurate 3D map of mountain, cave, and water surfaces would give engineers excellent data for planning.

 

The main web site is here, they now market the ZEB-REVO, not sure if the ZEB1 is still available:

https://geoslam.com/

 

There appears to be a second hand ZEB1 unit for sale here for ~10,000 USD:

https://surveyingepic.com/?59,geoslam-zeb1-3d-laser-scanner

 

Probably someone in Thailand has a unit to purchase, hire, or loan.

 

good luck,

  David Pont

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[Martin Isenburg]

Hello Khun Phisan.

there might be some speleologists / geologists / geomorphologists / hydrologists / etc ... on this list that can make a qualified statement on whether it is possible to detect correlations between a high-resolution ground model derived from a LiDAR DTM flown at 20 shots per square meters or so and the features of an underlying cave.  Whether or not airborne information provides enough clues for how deep below the ground a cave is - be it via changes in vegetation or slight depressions - to get ideas about the thickness of cave wall for drilling operations I have honestly no idea. I could imagine that for preventing additional storm water from reaching the cave system the locations of existing water sheds / canals derived from a LiDAR DTM surely must be useful, but this kind of science is far outside of my expertise.

Making a model of the inside of the cave would only seem to make sense if there are sufficiently many weeks left to plan an extraction. I doubt that the ZEB1 / GeoSLAM approach would be feasible for planning an under water extraction given that the news reports that the critical sections of the cave system are all under water and that this water is murky. Whether or not divers could carry a sonar device that also performs some form of self-registration computation to get accurate absolute geo-positioning is these GPS-denied environments I do not know. Does such thecnology exists? Modelling the air-pocket parts of the cave would obviously be easy with a ZEB1 / GeoSLAM but determining the exact position of these air pockets with respect to the ground DTM should be difficult. How much detail can be captured about a cave system with sufficient time for (dry) scanning can be seen in several videos:

https://www.youtube.com/watch?v=slkJRv4pbCE

https://www.youtube.com/watch?v=OPCb4x5g8W8

Does the Royal Thai Army/Airforce not already have LiDAR acquired above this area? Should you have access to such data I could certainly be of assistance in processing the best possible high-resolution DTM from it. 

Regards and best of luck to those trapped and their rescue team.

Martin 

[Dr. Antoine Cottin]

Hi Martin,

To some extend you would be able to get geological information from a DTM but you will need to have geological features arising from it, like rock outcrops. If you're a in dense forest with thick substrate (on which the trees grow), I doubt you'll be able to get any valuable information. The only technology, non-airborne, that would give you geological structural information from underground would be ground penetrating radar (https://en.wikipedia.org/wiki/Ground-penetrating_radar). For the watershed/canal structure, I'm sure a high density DTM would work.

For the murky water, again lidar or bathymetric lidar might be extremely limited if not unusable and therefore a high frequency/resolution sonar would be the best bet. I could think of the BlueView from Teledyne (http://www.teledynemarine.com/blueview/), but again not sur how easy/feasible this tech could be use in a GPS deprive environment.

Antoine

[Michael Perdue]

Hi Martin,

 

This technology has existed for some time. In the 90’s there was a group of Cave divers including Dr Bill Stone who ran the Wakulla Springs 2 project. For that project, a device called the Digital Wall Mapper was designed and built. It used 32 sonar transceivers mounted to a diver propulsion vehicle and pinged at 4Hz. It relied on an IMU for navigation and used magnetic induction to establish absolute positioning. 6.5km of passage were mapped at an average depth between 250-300’ with this device. The absolute accuracy of the data is believed to be 1m. It’s not in the same class as laser scanning, but far better than using knotted cave line, magnetic compasses and a healthy dose of artistic interpretation.

 

The ideas behind this project eventually morphed their way into the DEPTHX and ENDURANCE AUV’s, which autonomously mapped caves in Mexico and under the ice of Lake Bonney in Antarctica and use SLAM technology.

 

Unfortunately, those vehicles are far too large to haul through a dry cave to a sump, but he has continued his work in the field with smaller and smaller devices and regularly tests them in caves due to the navigational challenges that they pose. Here is the latest one I could find.

https://www.youtube.com/watch?v=rLQBeba66PI

 

Cheers,

 

Mike

 

 

From: last...@googlegroups.com <last...@googlegroups.com> On Behalf Of Martin Isenburg
Sent: July 7, 2018 7:51 AM
To: LAStools - efficient command line tools for LIDAR processing <last...@googlegroups.com>
Subject: Re: [LAStools] Lidar Mapping support rescue of 13 Thai boys trapped in Thamluang cav, Chiangrai, Thailand

 

“Whether or not divers could carry a sonar device that also performs some form of self-registration computation to get accurate absolute geo-positioning is these GPS-denied environments I do not know. Does such thecnology exists?”

 

[Nina Heiska]

Hi Phisan,

 Thank goodness they have now saved some of the boys! Hope it goes well today as well

 People in this forum may not be aware that search and rescue robots (including mapping) are a field of their own. So there is a lot of development, papers and even a robot league competition http://wiki.robocup.org/Robot_League if not several. I remember years ago, when Prof. Nuechter was visiting Finland, he mentioned that he was on his way to a practical "competition" in Sweden - the question was about mapping and rescuing operations in an underground mine.

 Of course Japan, the land of robotics, is also a good place to start looking for those interested. If you remember the Fukushima accident and the following events, one of the issues was to get a robot through "difficult" terrain and radiation to the check the core.

 I am not sure if any of the current solutions would work in Thailand, in the conditions described by the media. As always, real conditions provide hard challenges for the developers.

 Cheers,

 Nina

[Phisan Santitamnont]

Thank the professionalships of the intetnational rescue diver team.

Foe sake of future interest.

The ThamLuang cave is in the Limestone mountain.
The other rescue effort was find out cavities
that might access to the main cave.
Dozen of teams tried hard to find them
and climb dowh to exlpore hopelessly.

If we have lidar with dense point clound e.g. 10+
points per sq.m.
Would it be possible to identify cavities similar
to find canopy model which is mathematcally
reflective of the cavity

https://rapidlasso.com/2014/11/04/rasterizing-perfect-canopy-height-models-from-lidar/

Doest anyone possess lidar over similar limestone mountain
and could share the data or even the result.

[Martin Isenburg]

Khun Phisan,

Was there any LiDAR used in the end? This rather vague article that I saw tweeted about by @QuantumSpatial has a few (DTM or DSM?) hillshadings and somewhat out-of-context explains what LiDAR is, but it's not clear whether the shown maps are in fact derived from LiDAR. Does the Royal Irrigation Department have LiDAR for this area? My understanding was that their LiDAR is mainly covering the Chao-Phraya river delta. Or was there LiDAR data from the Royal Thai Military? Or does the article mention LiDAR because that technology was already used in that earlier French-led surveying effort that is mentioned that had apparently recorded the extent and cross section of the cave for Dr. Martin Ellis’ book "The Caves of Thailand" ... ?

http://www.networkworld.com/article/3291787/internet-of-things/the-vital-role-of-technology-in-the-thai-cave-rescue-mission.html

I also saw Intermap press release that wa pointing out the role of their data to the rescue efforts and it may be that those hillshadings are derived from their donated 1m elevation rasters. They write: "In partnership with our local partners, Mappoint Asia Thailand Public Company, and Chiang Rai University, Intermap supplied its newly-released NEXTMap One, a 1-meter resolution elevation dataset, to the Thai Department of National Parks on June 27th. This high resolution elevation data was supplied within three hours, and used in conjunction with other sensors to identify elevation coordinates, prioritize potential drilling points, identify drainage paths, provide a detailed and inter-active 3D model of the area, and determine alternate routes into the caves to help rescue the boys. NEXTMap One, which was provided for free, is substantially more detailed than the existing elevation data available from commercial and government sources." Not sure from what data those maps were created: 

http://www.intermap.com/pressreleases/2018/07/intermap-technologies-assists-in-rescue-of-thai-soccer-team

Regards,

Martin