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Author Topic: Streaks in orthomosaic  (Read 2449 times)

paulmartec

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Streaks in orthomosaic
« on: September 03, 2020, 09:52:42 AM »
Hi guys.  I’m hoping someone can assist helping me in understand what has caused these streaks in my data.  The next issue is if it can be fixed.  I’ve captured 11500 images so pretty keen to get it sorted.  Flown with 85% side overlap.  Thanks in advance.

leostalin91

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Re: Streaks in orthomosaic
« Reply #1 on: September 03, 2020, 10:37:56 AM »
Let Sent me single ortho mosaic tile with streaks I will remove it using photoshop
leostalin91@gmail.com

sven_a

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Re: Streaks in orthomosaic
« Reply #2 on: September 03, 2020, 11:33:49 AM »
Might be related to the mosaic blending method and illumination of the images?

Arie

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Re: Streaks in orthomosaic
« Reply #3 on: September 03, 2020, 11:39:07 AM »
Definitely looks like different exposure times (or cloud shadows) during image acquisition. Have you tried using Agisofts color calibration?

paulmartec

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Re: Streaks in orthomosaic
« Reply #4 on: September 03, 2020, 12:06:04 PM »
Might be related to the mosaic blending method and illumination of the images?
Im struggling to find information re the process. The manual seems to pass over these processes.

paulmartec

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Re: Streaks in orthomosaic
« Reply #5 on: September 03, 2020, 12:09:24 PM »
Definitely looks like different exposure times (or cloud shadows) during image acquisition. Have you tried using Agisofts color calibration?
I definitely did not change the exposure settings between flights, but the day was difficult weather wise, very cloudy and dull at times with rain threatening.  I will try the colour cal, again I find the manual lacking in this space and nothing that I can find on Youtube etc either in the way of a tutorial.  Im obviously new to Agisoft and have lots to learn.

paulmartec

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Re: Streaks in orthomosaic
« Reply #6 on: September 03, 2020, 12:12:04 PM »
Let Sent me single ortho mosaic tile with streaks I will remove it using photoshop
leostalin91@gmail.com
Thank you for your offer.  I havent played with AS settings yet and will attempt to rectify it within AS as first preference.

Arie

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Re: Streaks in orthomosaic
« Reply #7 on: September 03, 2020, 12:37:56 PM »
Well, then it's obviously the cloudy condition causing these streaks since the lighting condition changed during the flight.

As a recommendation to save some time: Copy the data to a new chunk (right-click on chunk, Duplicate...) and include the model. Delete most of the images, leaving only a subset of images where the streaks are (see attached image) and run the Calibrate Color (under "Tools") using "model" as source (include WB). It will be alot faster then running the entire dataset and it will be a possibility for you to see if that helps eliminating the streaks.
Cheers!

PROBERT1968

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Re: Streaks in orthomosaic
« Reply #8 on: September 03, 2020, 04:51:00 PM »


Have you tried another option is to draw a polygon in that area you drew, right click Assign images.  In that option, you can choose which one image to assign and enable it. How many images are in that polygon area ?

For me I use old aerial images I work on from my national forest and when I see like that , I go there and check which one to assign.

Then you can update the orthomosaic and see if you are satisfied or not .

Let me know if I can help you with that...

Cheers,

paulmartec

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Re: Streaks in orthomosaic
« Reply #9 on: September 04, 2020, 12:56:46 AM »


Have you tried another option is to draw a polygon in that area you drew, right click Assign images.  In that option, you can choose which one image to assign and enable it. How many images are in that polygon area ?

For me I use old aerial images I work on from my national forest and when I see like that , I go there and check which one to assign.

Then you can update the orthomosaic and see if you are satisfied or not .

Let me know if I can help you with that...

Cheers,
Hi PROBERT1968, thank you, I wasnt aware of that feature, I'll keep playing around and will post an update.  Learning lots :D

PROBERT1968

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Re: Streaks in orthomosaic
« Reply #10 on: September 04, 2020, 01:32:18 AM »
Sure no problem, They (Agisoft) have been updating a lot of new features and they add them to the version...

Let me know if you need help  I can try show you how in the video through the Instagram and provide the link to it here...


Good luck

paulmartec

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Re: Streaks in orthomosaic
« Reply #11 on: September 04, 2020, 05:18:16 AM »
Sure no problem, They (Agisoft) have been updating a lot of new features and they add them to the version...

Let me know if you need help  I can try show you how in the video through the Instagram and provide the link to it here...


Good luck
  Thanks again.  You can probably assist with another question that Im trying to get my head around with another data set that I ran is why my GCP markers dont agree with the final surface height after processing.  I checked the DEM against my original surveyed GCP points and have found discrepancies between 1 + 1.6 meters!  I read another post that said to untick all image reference data and force AS to use the GCP values.  If this is the case wouldn't that be the process every time?

dpitman

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Re: Streaks in orthomosaic
« Reply #12 on: September 04, 2020, 05:29:03 AM »
I ran is why my GCP markers dont agree with the final surface height after processing.  I checked the DEM against my original surveyed GCP points and have found discrepancies between 1 + 1.6 meters!  I read another post that said to untick all image reference data and force AS to use the GCP values.  If this is the case wouldn't that be the process every time?

It all depends on how accurate the position coordinates of the camera is.  If you're talking a consumer drone, the positioning accuracy is terrible.  It's suficient to allow the software to place the cameras position relative to the other cameras.  But compared to accurately surveyed GCPs, there is no comparison.  That's why you tell the software that the GCPs are precise, and the cameras need adjusting based upon them.

On the other hand, if you are using either a RTK or PPK workflow for your drone, the camera coordinates may be just as accurate as the GCPs.  So, in that case, you would tell Metashape that the cameras are equally as accurate as the GCPs and MS builds the model accordingly.

Hopefully that makes sense.

Dave
« Last Edit: September 04, 2020, 05:30:37 AM by dpitman »

paulmartec

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Re: Streaks in orthomosaic
« Reply #13 on: September 04, 2020, 05:32:10 AM »
I ran is why my GCP markers dont agree with the final surface height after processing.  I checked the DEM against my original surveyed GCP points and have found discrepancies between 1 + 1.6 meters!  I read another post that said to untick all image reference data and force AS to use the GCP values.  If this is the case wouldn't that be the process every time?

It all depends on how accurate the position coordinates of the camera is.  If you're talking a consumer drone, the positioning accuracy is terrible.  It's suficient to allow the software to place the cameras position relative to the other cameras.  But compared to accurately surveyed GCPs, there is not comparison.  That's why you tell the software that the GCPs are precise, and the cameras need adjusting based upon them.

On the other hand, if you are using either a RTK or PPK workflow for your drone, the camera coordinates may be just as accurate as the GCPs.  So, in that case, you would tell Metashape that the cameras are equally as accurate as the GCPs and MS builds the model accordingly.

Hopefully that makes sense.

Dave
Hi Dave, that's what worries me as they are PPK tagged images.  Im using a Quantun Trinity F90+.  GCP's surveyed in with GPS rover via CORS which was only 2kms away.

dpitman

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Re: Streaks in orthomosaic
« Reply #14 on: September 04, 2020, 05:57:43 AM »
I would process a subset of the project and exclude the cameras and see what result you get.  If equally poor results then you need to keep looking.  If the surface tighten's right up, then you may have isolated the problem to the drone.