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Author Topic: Overlaps images Question  (Read 2845 times)

PROBERT1968

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Overlaps images Question
« on: May 04, 2020, 09:38:41 PM »
I have a question. 

So what if your images are overlapping to each other but if you find some spotty areas that are smeared.  Like for example, you see a rock of the same place but looked smeared. What should you do to fix it ?

In my case, I have seen some areas that are smeared and some other areas looked fine...

Let me know if you need me to screenshot , I can .

Thanks
« Last Edit: May 05, 2020, 04:43:59 PM by PROBERT1968 »

James

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Re: Overlapps images Question
« Reply #1 on: May 05, 2020, 11:29:18 AM »
Everyone ...
I know you all like to post asking questions ...but I suggest you please screenshot your pictures so we all can understand what your problems are...

I'm going to guess that you mean blurred areas, due to motion blur or being out of focus.

In that case I would remove them from the project completely.

If there are too many to look through then i would use the "estimate image quality" tool (right-click in the photos pane) for "all cameras". Then switch the photos pane to details view, and sort by image quality. Then look through them, starting with the worst, removing them until you start to see only good quality images.

You can do this before or after alignment.

PROBERT1968

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Re: Overlaps images Question
« Reply #2 on: May 05, 2020, 05:04:21 PM »


James,

Here are the 3 screenshots of what I am talking about


James

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Re: Overlaps images Question
« Reply #3 on: May 05, 2020, 06:38:05 PM »
I'm not sure what I'm looking at.

Are those screenshots of an orthomosaic generated from old BW aerial photos, overlaid on a colour orthomosaic from a different source?

Is that why the markers are duplicated? Because it's two orthomosaics overlaid?

So you're seeing the smearing in the BW orthomosaic, but presumably not the BW input images?

I guess it must be either that the camera calibration is out, somehow, or the elevation data source that you are using (DEM/mesh?) is out, somehow.

Smear2.png looks really interesting... as if there is a big erroneous 'hill' in the elevation data source causing the stretching, but which is cut off by the Metashape region bounding box, causing the 'holes'.

I don't deal with aerial surveys or historic images or any kind of GIS stuff, so much as terrestrial architectural stuff, so this is all guesswork, but happy to play around with the project if you want to/can share files.

PROBERT1968

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Re: Overlaps images Question
« Reply #4 on: May 05, 2020, 08:10:36 PM »


What you are seeing is an actually orthomosaic of BW aerial photos.

The color you see in the background is a ESRI basemap.

So maybe it is my markers that are in bad place , if that is what you think ?

James

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Re: Overlaps images Question
« Reply #5 on: May 06, 2020, 11:25:42 AM »
Ah, I'd heard of the basemap feature but never used it.

Yes I suspect there could be issues with your markers as they appear to be duplicated.

In 'Smear1.png' you have two markers both called 'point 25'.

In 'Smear3.png' you have three pairs of markers:
  • Point 56 and point 56
  • Point 59 and point 59
  • two markers both called point 24

Maybe you merged chunks and didn't merge markers for points 24 and 25, and Points 56 and 59 wouldn't merge anyway because of the difference in the letter 'P'.

I couldn't say that this was certainly causing your issue, but it can't be helping.

The fix for that would be to go carefully through all the markers in the reference pane, and check for any duplicates. Each time you find a duplicate rename one of them by appending something like "_DUPLICATE" to the name (leaving the original part of the name intact, i.e. "point 24_DUPLICATE". Then for each duplicate marker, filter the photos by that marker and go through them replacing the duplicate for the other one, until the 'duplicates' have no projections listed in the reference pane, and then you can delete them.

Then you would need to optimise again, and rebuild your orthomosaic.

Make a backup first as it could be that I don't know what I'm talking about.

The replace marker feature is shown in the attachment in case you weren't aware of it. It is only available in the photo view (it just looks like the 3D model view in my screenshot because my input images in this example are 2D images of a 3D model, which might be confusing...)
« Last Edit: May 06, 2020, 11:30:43 AM by James »

PROBERT1968

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Re: Overlaps images Question
« Reply #6 on: May 06, 2020, 03:42:53 PM »
James,

That is quite an interesting .  What makes you think it is a duplicate ?

To be clear the word Duplicate, are you talking about the points that are being place twice or copied ?

Yes, I have two chunks , there are western and eastern.  I finished the eastern side, now I am working on the western side.  So if you are talking about chunk that will be merge or not, the western chunk, I have the points on the edge on the right side. Would that be the case that is causing smears ?

I was not planning to merge both because I think it will be too big to copy it and put it to the server and back it up on my external hard drive. This is for my co-worker.

I never thought this thing would affect it because on the edge side before merge with the other chunk .

Yes I plan to make it backup.  I always backup weekly to my external hard drive just in case If I need it back .

I'll get you a screenshot for the two chunks on my next reply.

James

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Re: Overlaps images Question
« Reply #7 on: May 06, 2020, 05:04:29 PM »
By 'duplicate' I just mean two different markers appearing in your screenshots that refer to the same point on the ground.

If you haven't merged the chunks, and they don't both exist in a single chunk, then I'm not sure why they would both show on the Orthomosaic view, unless 'show aligned chunks' is enabled (I don't have access to metashape right now to check if that would account for it).

It could be totally unrelated, i just thought it was odd.

Anyway, I stand by my original statement that:

it must be either that the camera calibration is out, somehow, or the elevation data source that you are using (DEM/mesh?) is out, somehow.

although you could maybe also add to that the possibility of misaligned cameras, and of course it could always be a bug in the software, but I don't think that's the most likely explanation.

PROBERT1968

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Re: Overlaps images Question
« Reply #8 on: May 06, 2020, 05:22:56 PM »
Thank you ... it is okay if you are not sure but your tips did help me to make me think about this..

On one other thing on my last post I stated that I had two chunks on this one... well I forgot to mention that when I open this Western , I copied the project and rename it to western project AND I deleted the Eastern chunk from it...

So I have just one chunk by itself...

I will review the smear areas and check that out on that area and see what happens

PROBERT1968

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Re: Overlaps images Question
« Reply #9 on: May 09, 2020, 02:43:58 AM »


@ James....

I just discovered and forgot about one thing.....if you see a spotty smeared area, you can draw it in that area in the Ortho View. Then right click on it and there is list there that says Assign the images . You can choose which one is fit in....

If not then go back and add a marker there .

I just did this today but still have not run it yet....

Will let you know more about this...