Greetings.

Does lidar surveying works to map sea bottom ? NOT from flying above water surface, but hovering under the surface ? ( as towed side scan sonar, as long as light propagation allows on reasonable transparency )

No

LIDAR uses IR light at around 1 micron, and the attenuation of such light is very strong. Much of the light would be absorbed or scattered before it traveled a meter

https://www.researchgate.net/figure/Penetration-depth-attenuation-length-of-electromagnetic-radiation-in-water-vs_fig1_258254992

Much of the EM radiation spectrum in general wouldn’t be very useful. (This is why they have to use ELF to send messages to subs to tell them get near enough to the surface to allow for easier communication)

Thank you. Well, learned something else today. Infrared based.

Can lidar be conducted over/across air in visible light ? It would be nearly plain photography then ?

4 minutes ago, Externet said:

Thank you. Well, learned something else today. Infrared based.

Can lidar be conducted over/across air in visible light ? It would be nearly plain photography then ?

It could, but IR has more efficient detectors and it more readily penetrates hazy and foggy atmosphere. Plus you don’t have bright lights flashing, which might bother (or alert) people

It’s not photography, though. You are measuring time-of-flight signal of a light pulse to measure a distance.

To amend my previous post, in checking something I saw a reference to bathymetric lidar, which uses green light to scan shallow water, like riverbeds and coastline.