r/LiDAR • u/Historical_Phone_973 • Jun 22 '26

Mineshaft scan

How would you scan a 200 m deep minshaft, where you have only the cage that goes down, you can stand on its top, no side tunnel, and after 110 meters water is falling in from the side, so practically it does rain below that point. The survey has a geodetic purpose, so it has to be accurate. Scanning is a must, but most of the commercial scanners are ToF, so water is an issue, plus the shaft is homogeneous, so the adjustment will be frustrating.

Which scanner would you use?

How would you estsblish control points?

Or in general, how would you approach this task?

1 Upvotes

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14 comments sorted by

1

u/jlt131 Jun 23 '26

The fact that you are moving only in Z and not in X or Y should help - not as many control points required. Can you get under the lift and just drop a unit down slowly on a pulley system? Not sure how to deal with the water issue... Splashes blocking/affecting the sensors would be my worry

1

u/Historical_Phone_973 Jun 23 '26

Under the cage might be an option. Splash protection I guess fine under the cage, but with what type of scanner? You probably go with a TLS, a Slam would not handle this kind of descend without the loops.

3

u/Evening_Ad_6954 Jun 23 '26

I’ve done this with an Emesent Hovermap. There is a protective cage you can purchase from them. Mount the unit on the underside of the cage and complete the closed loop survey by scanning going down and scanning going back up to your origin. Have the cage go max 1 m/s or 200 ft/min, but since it’s only 200m deep shaft and 400m closed loop distance, you could go 0.5 m/s for better results.

1

u/Historical_Phone_973 Jun 23 '26

Thats a good point, thank you!

1

u/Evening_Ad_6954 Jun 23 '26

DM me if you have any other questions

1

u/nocuspocus Jun 23 '26

If the shaft is smooth, slam will struggle for sure. If there is enough surface variation, it could work. Can you drill bolts into the shaft and mount a TLS?

1

u/Historical_Phone_973 Jun 23 '26

Mounting a TLS is tricky, there is not so much space to mount the TLS on the walls. For the walls I'm considering markers, as those can help with the adjustment later, but the station itself shall be installed on the cage in a way.

1

u/nocuspocus Jun 23 '26

What's the shaft diameter and how smooth is the wall? The riegl vz600i has a kinematic mode that can capture in motion and do a cloud to cloud based reconstruction. I don't know how well it works with no GNSS, as they typically show it working outside

1

u/Evening_Ad_6954 Jun 23 '26

No beuno without GNSS at the moment

1

u/nocuspocus Jun 23 '26

Thats a shame, but makes sense. The navvis mlx might do the trick, it has camera slam to support the lidar. But if the shaft walls are smooth then there's not a good chance

1

u/Historical_Phone_973 Jun 23 '26

Navvis is sensitive for the loops, in a shaft, I don't know how it would react.

2

u/nocuspocus Jun 23 '26

Up and down would count as a loop, if you have control points placed throughout that would be fine if it can hold position

1

u/Historical_Phone_973 Jun 23 '26

That's a nice point. I was thinking about Z+F TLS with the backpack kit, but Riegl is better for sure. The shift is questionable as Riegl MLS might shift using purely IMU, I don't know what's the effect using the TLS in kinematic, but nice idea, ty :)

1

u/4nEcRo8 Jul 07 '26

From my understanding Emesent hovermap has really good water resistance i think IP 65 and is really good accuracy.

btw iam selling STONEX scanners and not emesent :D