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Author Topic: Multispectral project with different focal  (Read 4536 times)

madekwe

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Multispectral project with different focal
« on: November 16, 2016, 07:57:21 PM »
Hi,

I have a 6 bands multispectral camera (triggering at the same time). 5 have normal frame, one is fish-eye. The idea is to fix the fish-eye band as the master channel in order to find the position of the cameras (normal band have no sufficient overlapping for an alignment)

It is posible ?

Thanks a lot.

Alexey Pasumansky

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Re: Multispectral project with different focal
« Reply #1 on: November 16, 2016, 08:12:18 PM »
Hello madekwe,

You can try to use "multispectral" chunk approach:
- put the images taken by the different cameras/sensors in the separate sub-folders to some "master folder",
- use Add Folder option from the Workspace pane and specify the path to the master folder,
- select from the dialog box the option that is called Create Multispectral Chunk from Folders as Bands.

This approach assumes that the distances between the camera sensors are very small and can be neglected compared to the distance to the area of interest. At the same time each sensor (called "plane" in PhotoScan for this approach) will have separate calibration data and also orientation angles would be estimated individually for the sensors.
Best regards,
Alexey Pasumansky,
Agisoft LLC

madekwe

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Re: Multispectral project with different focal
« Reply #2 on: November 16, 2016, 08:39:34 PM »
thanks for your quick reply,

I test this approach, and fix the fish eye as the master channel.

The 5 others bands (frame type) have very low overlapping and I have very bad results on some CPs (others are ok)
Placing the GCPs for in the fish-eye images is quite imposible...

On an other hand, i test a project with one chunck ans two sensors : a fish eye and a normal frame (both in the green band), the accuracy of the alignement is really good. The problem is that I have the orientation of juste 2 sensors. But using a melling fourier transform I find the translation rotation and scaling between the different sensors.

So i think I'll give up the multispectral project.

What is exactly the master channel ? Its looks like it is not posible to do a multispectral project using different frames (fish-eye, normal, spherical .. ) Am I right ?

Alexey Pasumansky

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Re: Multispectral project with different focal
« Reply #3 on: November 16, 2016, 08:41:31 PM »
Hello madekwe,

Following this approach you do not need to use Master Channel.

Master-channel should be used, when the multispectral data is loaded from multichannel TIFF file, where the channels are already properly aligned with each other (have the same resolution and interior orientation).
« Last Edit: November 16, 2016, 08:43:09 PM by Alexey Pasumansky »
Best regards,
Alexey Pasumansky,
Agisoft LLC

madekwe

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Re: Multispectral project with different focal
« Reply #4 on: November 17, 2016, 01:31:28 PM »
yes, that was my conlusion ! thanks to confirm it.

madekwe

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Re: Multispectral project with different focal
« Reply #5 on: November 17, 2016, 01:42:45 PM »
When you mean properly aligned with each other, you assumed that images have exactly the same orientation ?
Because this is not the case for multispectral images (like Micasense, Airphen ...). There is small offset, images in the same trigger are not properly co-registrated..

Alexey Pasumansky

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Re: Multispectral project with different focal
« Reply #6 on: November 17, 2016, 01:56:44 PM »
Hello madekwe,

As far as I know, MicaSense is not writing multi-channel TIFF file, but several single-channel files, so for such kind of data you need to use multispectral chunk approach. PhotoScan should recognize the images added from RedEdge or Sequoia cameras, even if they are added from the same folder and create multiplane chunk.
Best regards,
Alexey Pasumansky,
Agisoft LLC

madekwe

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Re: Multispectral project with different focal
« Reply #7 on: November 17, 2016, 02:17:35 PM »
Ok ! and when photoscan deal with multiplane chunk how photoscan deal with the co-registration of the images for one trigger ?

Is there an alignment for every plane ?

Alexey Pasumansky

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Re: Multispectral project with different focal
« Reply #8 on: November 17, 2016, 02:42:26 PM »
Hello madekwe,

Multiplace chunk requires synchronized triggering for all sensors, since the approach assumes that all the images have been taken from the same position at the same time. But the camera orientation angles and interior information may vary for the bands (planes).
Best regards,
Alexey Pasumansky,
Agisoft LLC

mwittnebel

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Re: Multispectral project with different focal
« Reply #9 on: November 18, 2016, 12:38:18 PM »
Hello madekwe,

You can try to use "multispectral" chunk approach:
- put the images taken by the different cameras/sensors in the separate sub-folders to some "master folder",
- use Add Folder option from the Workspace pane and specify the path to the master folder,
- select from the dialog box the option that is called Create Multispectral Chunk from Folders as Bands.

This approach assumes that the distances between the camera sensors are very small and can be neglected compared to the distance to the area of interest. At the same time each sensor (called "plane" in PhotoScan for this approach) will have separate calibration data and also orientation angles would be estimated individually for the sensors.

Dear Alexey, I could not find the Dialog box with the option "Create Multispectral Chunk". At what Version is this available ?
At the moment, I have Version 1.2.4 build 2399 installed.

Best Regards,
Marcus

Alexey Pasumansky

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Re: Multispectral project with different focal
« Reply #10 on: November 18, 2016, 12:42:11 PM »
Hello Marcus,

Please update to the version 1.2.6.
Best regards,
Alexey Pasumansky,
Agisoft LLC