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Author Topic: Registering laser scans  (Read 3266 times)

flogs

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Registering laser scans
« on: February 05, 2022, 11:43:03 AM »
Hi,

I am not an expert, rather starting experimenting with combining photogrammetry (aerial+terrestrial) with terrestrial laser scan (TLS) data. I am a surveyor and I need a centimeter accuracy of point clouds of buildings. Is Metashape fully usable for this purpose? I see in other threads that many people have doubts about it. My question is how accurate is scan registration from structured ptx or e57 formats. Only

I have access to data from Faro Focus M 70. Maybe an older model, I am not sure about camera parameters. But it takes too long to capture colored 360° panoramas from the scanner. Therefore we have only infrared panoramas which are much quicker to take. But additionaly we are using 360° panoramas (from photos or videos) from an external 360° camera (outside scanner). We are using this for scan registration outside of Metashape.

But I would like to try to do as much as possible only in Metashape. External 360° panoramas from inside of the building are not good to be used in generating points in final point clouds (along with TLS data). They should be used only for registering scans. I do not know if this is possible. If I do not add that 360° photos, TLS data are registered anyway (from IR panoramas) but only with very little number of tie points. But I have doubts about how accurate that can be.

Filip
« Last Edit: February 07, 2022, 03:01:13 PM by flogs »

flogs

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Re: Registering laser scans
« Reply #1 on: February 08, 2022, 09:58:19 AM »
Ok, I did not get meaningfull answer here or from Agisoft email support. It looks like combining laser scan data in Metashape is still in very early stages and right now it is not in rapid developement. Some threads about this are without a single answer and some people have doubts about practical usability of current solutions.
https://www.agisoft.com/forum/index.php?topic=12997.60

I will try to experiment with it but probably I will have to wait until maybe some new features pops up in Metashape. I can encourage you in this efford because it is quite essential for many land surveyors. So far I don't know e.g. how to assign priority to laser scanner data over 360° photos inside a building.
« Last Edit: February 08, 2022, 01:45:07 PM by flogs »

Alexey Pasumansky

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Re: Registering laser scans
« Reply #2 on: February 08, 2022, 02:45:53 PM »
Hello Filip,

Do you need to perform the co-registration of the laser scan data with the digital photographs or you prefer to keep the external registration information for scanner locations and to "align" the photogrammetric camera alignment to the fixed relative and absolute orientation of the laser scan data?
Best regards,
Alexey Pasumansky,
Agisoft LLC

flogs

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Re: Registering laser scans
« Reply #3 on: February 08, 2022, 04:41:51 PM »
Hello Filip,

Do you need to perform the co-registration of the laser scan data with the digital photographs or you prefer to keep the external registration information for scanner locations and to "align" the photogrammetric camera alignment to the fixed relative and absolute orientation of the laser scan data?

Hi,
I am looking for robust combined processing of photogrammetry data and LS data. All done in Metashape. I have usually GCP around and on fasade of the building. Building is scanned from outside and inside, UAV an camera photogrammetry from outside and 360° video mainly from inside. I am going to test now how registration of LS data will work for about 40 LS standpoints with only IR 360° panoramas. If alignment will not be succussfull or reliable, I can try to add 360° RGB data from video. But as support wrote me over email, there is no option to assing priority to LS data over photogrammetry data in the same area. I do not want photogrammetry from 360° video mess up with LS data in the interior. Video should be only used for aligning. (Maybe coloring LS data.) I will try to achieve that by disabling the 360° panoramas from external source after alignment process. But of course keeping it e.g. for purpose of removing artefacts from LS data (mirror and glass reflections) build be preferable.