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Author Topic: Some questions regarding combining laser scans and photogrammetry  (Read 1813 times)

John_H

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Hi, I've searched the forums and online, but can't find relevant answers to a couple of questions. Some refer specifically (I think) to using scans from a Leica BLK and Cyclone Register, some are more general.

1. I've exported scans from Cyclone Register as E57, with the setting to include panoramic images and as seperate files (if I don't use this option, no images are present at all) and with and without E57 compatibility mode. When I import the scans into Metashape 2.0*, the scans appear with cube map images (with depth maps), ie 6 individual images from the 6 orthogonal directions. Also, whilst the images appear in the correct place in relation to the point cloud, the actual scanner position, which in the documentation appears as a blue sphere, is missing.

2. In terms of processing, do people down sample their scans? Our individual scans have approx. 60m points, and we may be using 10 scans or more in processing. In my current project, I'm using approx. 1700 images and 3 scans. I did the alignment process in low accuracy, and it took about 20 mins, but at high it was around 70% complete after 72 hours, and the remaining time was 24 hours and increasing! Even when I downsampled the scans to 1/64th, ie, around 900k points each, the processing time at high accuracy was still prohibitive. (and the downsampling seemed to destroy the depth maps?) We have a powerful PC with 128GB, an i9 processor and a 16GB GPU, and processing the project with only the images at high accuracy takes just a few hours.

3. With the alignment done on low accuracy, I then generated a dense point cloud, but it wasn't aligned with the laser scans well at all, with an offset of 10s of cms at one end of the cloud.

Just processing the model with the photos has been very succesful, but I was hoping combining it with the laser scans would improve accuracy and provide scale, but at the moment it seems more trouble than it's worth...  Is this a problem with the BLK export/import? 

Sorry for the long post!

*Also, when I tried importing the acans into 1.8, the images didn't appear at all, which is an issue as I will have to go back to that version when my 2.0 trial expires
« Last Edit: February 02, 2023, 02:00:40 PM by John_H »

Kiesel

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Re: Some questions regarding combining laser scans and photogrammetry
« Reply #1 on: February 06, 2023, 10:39:48 AM »
Hi John_H,

which BLK was used, because it is a family of different devices (BLK360, BLK2Go, BLK3D,...)

Best regards,

KIesel

John_H

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Re: Some questions regarding combining laser scans and photogrammetry
« Reply #2 on: February 06, 2023, 03:01:48 PM »
Sorry, it was the BLK 360

Kiesel

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Re: Some questions regarding combining laser scans and photogrammetry
« Reply #3 on: February 06, 2023, 04:34:01 PM »
Hi John_H,

so then the pointcloud is a "traditional" structured TLS pointcloud and not an arial pointcloud as you get with the BLKFLY or BLK2GO (and for which you need version 2.0)

I have imported a 3,6 GB pointcloud made with a RTC360 in E57 format, exported in Cyclone, on a much smaller PC (32 GB RAM, GTX 1080 8192 MB) in Metashape 2.0 successfully. The pointcloud was referenced in Cyclone before to a local house system and was then imported in Metashape. The photos were then aligned to the pointcloud (3 photos were not).  DEM and orthomosaic were derived from classified laser pointcloud.

Quote
*Also, when I tried importing the acans into 1.8, the images didn't appear at all, which is an issue as I will have to go back to that version when my 2.0 trial expires

Existing users of Metashape (versions below 2.0) can upgrade to version 2.0 at no cost.

Best regards,

Kiesel
« Last Edit: February 06, 2023, 05:40:38 PM by Kiesel »

John_H

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Re: Some questions regarding combining laser scans and photogrammetry
« Reply #4 on: February 06, 2023, 06:13:21 PM »
Thanks Kiesel.

No, it's not aerial photogrammetry, so I was expecting a panoramic image.

And the alignment did work, on low settings, but anything higher the alignment time was probitive, and even when aligned, the resulting dense point cloud was misaligned with the laser scans.

And unfortunately I use a floating license, and we will not be able to update our license server when the new version is released.

John


Kiesel

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Re: Some questions regarding combining laser scans and photogrammetry
« Reply #5 on: February 07, 2023, 09:57:30 AM »
Hi John_H,

Is the statement of Agisoft

Quote
Free update
Update from Metashape 1.x to Metashape 2.0 is completely free and does not require any additional payments from the licensed users.

really not valid for a floating license?

Quote
No, it's not aerial photogrammetry, so I was expecting a panoramic image.

This is what I would expect as well. Perhaps it has to do with the export out of Cyclone?

Best regards

Kiesel

Alexey Pasumansky

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Re: Some questions regarding combining laser scans and photogrammetry
« Reply #6 on: February 07, 2023, 01:06:20 PM »
Quote
unfortunately I use a floating license, and we will not be able to update our license server when the new version is released.

Hello John,

We are planning to release a new license server utility to support Metashape Pro 2.0 floating licenses in about a week. You will just need to re-input the same floating license keys on the activation page in the new floating server interface. Meanwhile you can use trial license, if you would like to check 2.0 version functionality.
Best regards,
Alexey Pasumansky,
Agisoft LLC

John_H

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Re: Some questions regarding combining laser scans and photogrammetry
« Reply #7 on: February 09, 2023, 12:59:06 PM »
Hi Alexey,

Thanks for the reply - unfortunately the license situation is a bit more complex and we won't be able to install the new license server utility, so will have to go back to 1.8 for now (is it the case that projects saved in 2.0 can't be opened in earlier versions?)

Did you have any ideas about my laser scan problem?
I know Leica scanners and e57s exported from Leica Cyclone have been used succesfully with Metashape (https://www.int-arch-photogramm-remote-sens-spatial-inf-sci.net/XLVI-2-W1-2022/105/2022/), so I don't know if it's something specific to the BLK scanner which (I think) has it's own version of Cyclone Register. I can share a copy of the laser scan data if that would help?

I've attached a screen shot showing the project as-is, in the model I've highlighted the cube map images from the scanner.

Thanks,
John

Alexey Pasumansky

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Re: Some questions regarding combining laser scans and photogrammetry
« Reply #8 on: February 14, 2023, 06:24:56 PM »
Hello John,

If you can share some sample data from your dataset or similar to it, please send the download link to support@agisoft.com and we will check, if it can be processed in Metashape 1.8.

Projects from version 2.0 can be only saved in compatibility mode (via Save As dialog) to be opened in older versions.
Best regards,
Alexey Pasumansky,
Agisoft LLC