SLAM and LiDAR Cave Mapping

[dylanfromwinnipeg]

Your talking about what the oil and gas industry have been successful at doing, but pretty much no one else.

Voyis did seem to have something going, but they appear to have pivoted to photogrammetry only.

To date, there are only three companies that make proper laser scanners.

My iPhone has a laser scanner that I use in combination with the camera for photogrammetry.

But of course that won’t work underwater. Lots of laser options above ground, very few (and expensive) for underwater.

 

[wetb4igetinthewater]

My iPhone has a laser scanner that I use in combination with the camera for photogrammetry.

But of course that won’t work underwater. Lots of laser options above ground, very few (and expensive) for underwater.

Does it work underwater?

 

[Winmit]

i am just starting to read on the topic. I saw u mentioned using blue laser, which is understandably best option, but how you deal with the mud? or the small particles in the water.

 

[wetb4igetinthewater]

i am just starting to read on the topic. I saw u mentioned using blue laser, which is understandably best option, but how you deal with the mud? or the small particles in the water.

So there are limits to underwater laser scanning. The limits are:
1. Visibility
2. Ambient light.

The answer to both is more power. But there are limits. Here's an image of a propeller scan performed in Lake Union last May.

 

[wetb4igetinthewater]

My iPhone has a laser scanner that I use in combination with the camera for photogrammetry.

But of course that won’t work underwater. Lots of laser options above ground, very few (and expensive) for underwater.

There are two: Newton Labs and Voyis.

 

[rjack321]

So there are limits to underwater laser scanning. The limits are:
1. Visibility
2. Ambient light.

The answer to both is more power. But there are limits. Here's an image of a propeller scan performed in Lake Union last May.
View attachment 855349

If you can reach out and touch the cave wall, "measuring" that distance is rather easy and using a $100k laser is a waste of money. Its the "over that way" distances which are relevant to the OP

 

[wetb4igetinthewater]

If you can reach out and touch the cave wall, "measuring" that distance is rather easy and using a $100k laser is a waste of money. Its the "over that way" distances which are relevant to the OP

It all depends on what you are doing with the data

 

[rjack321]

It all depends on what you are doing with the data

The number of underwater cave maps with even meter level precision worth a break-even price of even 100K in the entire world is zero.

 

[wetb4igetinthewater]

The number of underwater cave maps with even meter level precision worth a break-even price of even 100K in the entire world is zero.

If that is the application, sure. If used by scientists, then...

So Richard, I know about this topic morre than you, so sit down, class is about to begin

A fixed line laser scanner like the Voyis Insight or the Newton Labs PL3200UW-LW generate scan data. This must be correlated to position information. Now there are two ways, IMU and USBL. The latter involves one or two beacons. Not practical in a cave. The former just racks up error over time. There'll be a massive error in the model from the beginning to the end, but that's probably okay for mapping.

There are no cheap underwater scanners.

So forget laser and use photogrammetry which will also have massive error but will be cheap. The Voyis stereo camera system is probably the best bet. That's what is being used on the Titanic. It is what NOC is using on Boaty McBoatface in an upcoming expedition.

Class dismissed.

 

[Manatee Diver]

Random idea, if it were possible to time sync a stereo camera system and a DPV INS system (like the Suex one), would be allow for on the move capture of the data? Perhaps with some manually surveyed check points every say, few hundred feet for correction? Any maybe have those check points also possible check that checkpoints for the radio beacon system that I've seen KUR use.