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Author Topic: Adding (Manual) Tie Points in Photoscan  (Read 11049 times)

BobvdMeij

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Adding (Manual) Tie Points in Photoscan
« on: June 21, 2017, 06:14:54 PM »
Anyone of you familiar with Pix4D probably knows what I am on about, is there something as Manual Tie Points (MTPs) in Agisoft Photoscan. With that I mean points/ locations one can manually pinpoint on multiple images to aid in the alignment, without them being GCPs.

I found my model to have some serious trouble in reconstructing a certain object, plausibly partially due to different lightning conditions, and I want to 'help' the software by manually selecting points of interests on different locations. No GCPs are present in the specific scene, hence I would like to make use of certain objects/ pixels that are clearly visible in multiple images but that were unfortunately not detected by Photoscan as key points.

I attempted to just add markers to these locations, as I would normally do with GCPs, in an attempt to activate these in the Reference Pane prior to Camera Optimization. Unfortunately, however, Photoscan does not let me select these markers to be used for Camera Optimization because they are (obviously) not provided with coordinates whatsoever. In Pix4D, this is a relatively straightforward process. First the software runs camera alignment, afterwards the operator can manually add additional tie points if he/ she is not happy with some or believes some crucial ones were missed. I have not been able to locate such a feature in Photoscan thus far.

Anyone any ideas?

Alexey Pasumansky

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Re: Adding (Manual) Tie Points in Photoscan
« Reply #1 on: June 21, 2017, 06:16:48 PM »
Hello BobvdMeij,

Markers do not require to have their coordinates input in the Reference pane (and be checked on there). If marker has more than one projections, it will be used as a valid tie point during Align Photos or Align Selected Cameras operations.
Best regards,
Alexey Pasumansky,
Agisoft LLC

BobvdMeij

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Re: Adding (Manual) Tie Points in Photoscan
« Reply #2 on: June 21, 2017, 06:24:36 PM »
Hello BobvdMeij,

Markers do not require to have their coordinates input in the Reference pane (and be checked on there). If marker has more than one projections, it will be used as a valid tie point during Align Photos or Align Selected Cameras operations.

But what about Camera Optimization? I already ran Align Photos to get a sparse cloud to more easily filter photos by a specific point and mark the tie points therein. Thereafter I would like to run Camera Optimization as I normally would.

Align Selected Cameras only allows me (according to the manual) re-align a subset of images, provided that the markers are pinpointed on these images. However, I have an entire array of photos that are misaligned (the model has effectively resulted in two seperate models/ sparse point clouds). I need to align both, but the markers may only be pinpointed on a few images.

I will be able to add some screendumps for illustration purposes tomorrow, but the situation is at follows.

The images were captured off a steel bridge, comprising of nadir flight, as well as of 45, 30 and 0 degrees flight lines at either end. I also mapped the pilars underneath using orbit flight and camera positions between 0 and 45 degrees. Part of the images taken of the pilars aligns with the 0 and 45 degree images of the super structure on top. HOWEVER, the flights of the upper part and the part underneath appear as two seperate spare clouds with a 90 degree swift in between.
« Last Edit: June 21, 2017, 07:10:32 PM by BobvdMeij »

Alexey Pasumansky

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Re: Adding (Manual) Tie Points in Photoscan
« Reply #3 on: June 21, 2017, 07:10:12 PM »
Hello BobvdMeij,

Then you need to reset the alignment for the cameras that are incorrectly aligned and use Align Selected operation for NA (not aligned) cameras.

Optimization of the incorrect alignment will give you even more distorted model.
Best regards,
Alexey Pasumansky,
Agisoft LLC

TimCull

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Re: Adding (Manual) Tie Points in Photoscan
« Reply #4 on: March 17, 2018, 02:49:14 PM »
I faced a similar query - with adding manual tie points (i.e points that I recognise to be common between images but Agisoft misses them)

At what stage is this best done in the workflow? Prior to first photo alignment? or After first photo alignment/prior to optimization?

SB

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Re: Adding (Manual) Tie Points in Photoscan
« Reply #5 on: September 26, 2018, 06:47:37 PM »
I usually perform the alignment step first and if there are problems I go to work adding markers.  Then I reset the whole alignment and realign the project again if it will not take too long.  Otherwise, I select appropriate images and reset the alignment for them and then run alignment on just those.