Scan Colourisation

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Scan Colourisation

Post by [email protected] » Sat Nov 09, 2019 10:16 pm

We have a large project where we are surveying a harbour both above and below the waterline. We have run a MM system on a boat and are now infilling sections that were obstructed at the time, now the survey area has been cleared.

We have window scans collected with a faro 150s. We are trying to colourise them with images take at the same location / setup. The subject we are scanning is circa 90m from scanner so colourisation with inbuilt camera is poor, this why we are using high spec dslr with big lens so pixel count to point spacing is comparable.

We have been using the manual point picking process in Realworks but have hit difficulties when merging overlapping scans together as colourisation between scans does not match up, despite picking good points pairs.

Any thoughts or advice would be appreciated or pointers to recommended software that would perform the task.

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Re: Scan Colourisation

Post by Scott » Sat Nov 09, 2019 10:40 pm

Why is color needed at all? Greyscale is probably your best bet, at half the time.

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Re: Scan Colourisation

Post by [email protected] » Sun Nov 10, 2019 9:11 am

It would be nice. Specification dictates unfortunately.

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Re: Scan Colourisation

Post by robjlg » Sun Nov 10, 2019 8:49 pm

Hello,

I use SCENE not Realworks. In my workflow, first I clean the scenes, apply filters and make registration. Only after, registration are done, I apply colors.

What scan resolution did you use? 1/4, 1/2 ?

When exporting color photos at full resolution you can see that horizontal resolution is >~ 20.000 pixels. Only the scan resolution 1/1 is higher. If you are using 1/4 scan resolution (10.240 points), the pictures take by the FARO S 150 used to colorize it has twice as many points. That is, point spacing x pixel count is already comparable.

Naturally, a picture take by an DSLR with an telephoto will show far more details. Did you compare the point cloud result from those two methods for a single scene ?

Roberto

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Re: Scan Colourisation

Post by [email protected] » Sun Nov 10, 2019 10:20 pm

Roberto

Thanks for your considered response.

We have used 1/1 resolution given the range and a full frame sensor 35mp dslr with a 200mm lens.

I haven’t done the pixel to point ratio yet but I will look into it. My instinct from seeing the data is that the images are higher resolution than the point cloud.

All the best

Alex.

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Re: Scan Colourisation

Post by Jason H » Mon Nov 11, 2019 12:40 am

Do you have several individual images you are trying to match or have you merged them into one larger image?

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Re: Scan Colourisation

Post by [email protected] » Mon Nov 11, 2019 7:35 am

We have both.

We are scanning vertical sections of wall for condition assessment, some 20m sections, some longer.

Where the field of view of the 200mm lens covers the wall section we have one image, where longer we have stitched a pano together.

In both cases we have shot the section from two angles to double up data so point count becomes comparable to pixel count and to provide redundancy should something go wrong.

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Re: Scan Colourisation

Post by jaredmatthews » Mon Nov 11, 2019 9:16 am

[email protected] wrote:
Sat Nov 09, 2019 10:16 pm
We have been using the manual point picking process in Realworks but have hit difficulties when merging overlapping scans together as colourisation between scans does not match up, despite picking good points pairs.
By this do you mean that each individual image does not overlap well with its corresponding scan, or is it that when you display the registered clouds after colourisation the colours do not balance between scans (ie some are more darker/brighter than their neighbours)?

I could suggest the following:

In the first instance, when colourising the images, you may need to do some manual tweaking after picking the corresponding points. If this does not match up still, then I suspect that the Nodal point between the scanner and camera may be unsynced.

See this posts for reference:

viewtopic.php?f=49&t=7340&hilit=photo+parallax&start=10

And these links to better understand the nodal point:

http://rosaurophotography.com/html/technical7.html
http://www.johnhpanos.com/epcalib.htm

On thing to try off the bat is to stitch the images using PTGUI (https://www.ptgui.com/)

In the second instance, there is a process in [Registration Mode], under [Imaging] Tab, in the [Matched Images] Group called Equalise image colour.
This will try balance the colour and brightness between all images (though be warned, I have had some very stranger results on this.


If you are still struggling, I wouldn't mind having a look if you could send me one or two scans and their corresponding images.

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Re: Scan Colourisation

Post by [email protected] » Mon Nov 11, 2019 2:28 pm

Thanks, it the later we are having issues with: "when you display the registered clouds after colourisation the colours do not balance between scans"

Or more so that the actual colourisation between scans does not match well, despite clouds registering well. e.g. a line of mortar between bricks 'jumps' between scans where it should be smooth./

Would be delighted i you looked at some data - I will bundle some up.

PM me your email.

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Re: Scan Colourisation

Post by [email protected] » Thu Nov 14, 2019 11:24 am

We have now tried full dome scan with partial pano but realcolor seems to spread the partial pano over the whole tzf irrespective of points picked.

Has anyone had success with partial pano with full dome scan in realcolor?

thanks.

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