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Author Topic: RED and NIR Photos won't Align for Orthomosaicing  (Read 2276 times)

meokeefe11

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RED and NIR Photos won't Align for Orthomosaicing
« on: January 21, 2018, 01:01:29 AM »
Agisoft Photoscan was successful in processing TIFF images for a RGB dataset, but has been consistently unsuccessful in aligning all photos of the data set with respect to NIR and Red images. I have done this process with and without reference data for my images.I will include a CSV for your reference in the link below.  I used MAPIR Survey 2 cameras and a 3DR Solo UAS to collect the imagery on a generally sunny day in upstate NY. The TIFFs were created using MAPIR's plugin for QGIS and have coordinate and altitude information in the properties. The multispectral imagery is required for calculating NDVI over willow crops.

Here is a link to My Data Set: https://drive.google.com/drive/folders/18nwRnepFrK6HFd1XZRiA2lSdLrCdWgzS?usp=sharing

Any assistance or advice you could give would be incredibly helpful. Thank you.
Megan O'Keefe
MS Candidate, SUNY College of Environmental Science and Forestry

Alexey Pasumansky

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Re: RED and NIR Photos won't Align for Orthomosaicing
« Reply #1 on: January 26, 2018, 10:03:38 PM »
Hello Megan,

I would suspect that the overlap between the images is too low for such complex terrain type. Usually dense vegetation requires even higher overlap than our recommended values.
Best regards,
Alexey Pasumansky,
Agisoft LLC

meokeefe11

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Re: RED and NIR Photos won't Align for Orthomosaicing
« Reply #2 on: January 29, 2018, 05:38:15 PM »
Hi Alexey-

We used an overlap of 70% for all imagery. As I mentioned, I was able to get an orthomosaic from some visible band imagery, but not for the multispectral data. Any further insights?

-Megan
Megan O'Keefe
MS Candidate, SUNY College of Environmental Science and Forestry

Alexey Pasumansky

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Re: RED and NIR Photos won't Align for Orthomosaicing
« Reply #3 on: January 29, 2018, 06:09:35 PM »
Hello Megan,

For the provided image sets I wasn't able to align TIFF sets individually neither for RGB, nor for NIR.
Best regards,
Alexey Pasumansky,
Agisoft LLC

meokeefe11

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Re: RED and NIR Photos won't Align for Orthomosaicing
« Reply #4 on: January 29, 2018, 06:31:38 PM »
Alexey-

Do you have any ideas as to why, other than the overlap not being sufficient? I would assume 70% is fine, from everything I have read. Could it be something to do with the darkness of the TIFF images?
Megan O'Keefe
MS Candidate, SUNY College of Environmental Science and Forestry

Alexey Pasumansky

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Re: RED and NIR Photos won't Align for Orthomosaicing
« Reply #5 on: January 29, 2018, 06:47:06 PM »
Hello Megan,

Usually we recommend 80% forward overlap and 60% side overlap for common aerial surveys. But for dense vegetation it may be insufficient, since the greenery looks different even for quite close camera positions.
Also images themselves look quite noisy.

I don't think that the "darkness" (used color range) is causing the issue, you can adjust the brightness for the images in PhotoScan and check how the images look like.
Best regards,
Alexey Pasumansky,
Agisoft LLC

meokeefe11

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Re: RED and NIR Photos won't Align for Orthomosaicing
« Reply #6 on: January 29, 2018, 06:50:49 PM »
Alexey-

Is there a means by which you would suggest reducing the noise in the photos? The images were taken with MAPIR Survey2 Cameras, and their website recommended the 70 % side and front overlap.
Megan O'Keefe
MS Candidate, SUNY College of Environmental Science and Forestry