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Author Topic: Alignment Error on aerial photogrammetry  (Read 1936 times)

singaii

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Alignment Error on aerial photogrammetry
« on: September 23, 2022, 06:21:12 PM »
Hi, first post here.
I try to make a mesh reconstruction from aerial image. I got  EO information with image name, yaw pitch roll and all information needed to align camera
I test the first batch on 65 caméras (nadir/right,left,forward,backward) and get a nice alignment and process straight from tie point, to densecloud, mesh and texture.





Confident on my good result i go to a larger set of 550 images, process them with EO information in the same way of first batch and got some gosthing alignment visible after densecloud processing



how i can get the correspondance between point i see in the model and camera it come from ?

Is there a way to verifie if EO data have right parameters for the right image in metashape ?

Thanks
« Last Edit: September 23, 2022, 06:27:05 PM by singaii »

Paulo

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Re: Alignment Error on aerial photogrammetry
« Reply #1 on: September 23, 2022, 08:17:18 PM »
Hello singaii,

if your eo file has precise position and orientation (XYZ, OmegaPhiKappa or YawPitchRoll) for each camera/photo (type Applanix POS) then I would suggest you import them into reference (setting correct CS) and then use https://github.com/agisoft-llc/metashape-scripts/blob/master/src/quick_layout.py to set the estimated reference from source. Then use Build Point Cloud from Tools/Tie Points menu and then the dense cloud  generation should be OK....

Hope this can be helpful,
« Last Edit: September 23, 2022, 08:26:00 PM by Paulo »
Best Regards,
Paul Pelletier,
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singaii

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Re: Alignment Error on aerial photogrammetry
« Reply #2 on: September 26, 2022, 02:27:53 PM »
Thanks Paulo for your quick response ! i make another project with your your workflow precision, in the precedent project i import photo, create reference and then make camera folder with corection of constructor (leica citymapper-2 calibration certificate) for each angle (nadir, forward, backward...) may be is this calibration step who ruin my last test. I will have the answer in few hours. Again Thanks a lot

singaii

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Re: Alignment Error on aerial photogrammetry
« Reply #3 on: September 28, 2022, 10:24:23 AM »
I process and got alignment but absolutly no tie point ...

Paulo

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Re: Alignment Error on aerial photogrammetry
« Reply #4 on: September 28, 2022, 10:50:27 AM »
Hello,

exactly what was your workflow? after importing precise eo into reference and running quick_layout script did you do Build Point Cloud from Tools>Tie Points...menu?
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Paul Pelletier,
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singaii

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Re: Alignment Error on aerial photogrammetry
« Reply #5 on: September 28, 2022, 02:59:26 PM »
my workflow basically is this one : I import image with workflow add photo, in workspace i do a right click an choose import reference, choose my EO file, define the right coordinate system, check omega phi kappa and click ok. this import point in my model, then in Tools -> camera calibration i make camera adjustment from leica citymapper 2 calibration certificate where i can found nadir and other view nominal focal lenght and pixel size and i define those parameter for each camera, yhen i click on workflow-> align to get tie point.

I test your workflow with importing photo, eo, launch script and go to tool -> tiepoint -> generate pointcloud and.. il make a total mess
 

singaii

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Re: Alignment Error on aerial photogrammetry
« Reply #6 on: September 28, 2022, 03:07:41 PM »
I test to process without camera calibration and i got two tie point layer, nadir photo don't have the same focal than the other camera so it's normal but i can see the same ghosting problem in the forwrd/backward/left/right layer of tie point. My EO may have some problem, image missing, gap in information... i don't know... and i can't get tie point information to knwo wich photo generate this specific tie point...

Paulo

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Re: Alignment Error on aerial photogrammetry
« Reply #7 on: September 28, 2022, 03:38:51 PM »
Hi,

I would check your oblique camera calibration. A focal length of 189 mm seems very large to me! and I would uncheck fixed camera parameters in Camera Calibration window,  do another optimization and you should get correct values for focal....
« Last Edit: September 28, 2022, 04:22:52 PM by Paulo »
Best Regards,
Paul Pelletier,
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singaii

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Re: Alignment Error on aerial photogrammetry
« Reply #8 on: September 28, 2022, 04:28:41 PM »
This is from Leica calibration certificate
https://leica-geosystems.com/products/airborne-systems/leica-citymapper-2

6.5 Estimation Results for Forward Camera

View Direction Forward
Radiometric Calibration Date 20.06.2020
Geometric Calibration Date 24.08.2020
Geometric Calibration File
MFC150_GEO_CH-S150015-A-891059_LENS-189012-A-918064_20200824-121350.xml
IMU Misalignment [degree]
ω 0.55168
Φ -0.03595
κ 0.12981
Red Green Blue
Calibrated Focal Length [mm] c 181.035 181.035 181.035
Principal Point [mm] x 0.00120 0.00120 0.00120
y 0.00208 0.00208 0.00208
Radial Symmetric Distortion a0 2.597348E-05 2.597348E-05 2.597348E-05
a1 7.996028E-09 7.996028E-09 7.996028E-09
a2 -9.347627E-13 -9.347627E-13 -9.347627E-13

6.5.1 Specifications for output image Value

Nominal Focal Length [mm] 189.000
Pixel size [mm] 0.00376
Rows [pixels] 10640
Columns [pixels] 14192
Nominal Principal Point x [mm] 0.00000
Nominal Principal Point y [mm] 0.00000
as you can see the nominal focal lenght for forward camera is 189mm... nothing strange for me

Paulo

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Re: Alignment Error on aerial photogrammetry
« Reply #9 on: September 28, 2022, 04:46:57 PM »
Hey singaii,

You are right... if you can share a small data set of your 5 camera system I could have a look...

Something is definitely wrong with either eo or io info.... If the oblique has 189 mm focal what about the nadir focal^?
Best Regards,
Paul Pelletier,
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singaii

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Re: Alignment Error on aerial photogrammetry
« Reply #10 on: September 28, 2022, 05:16:59 PM »
Unfortunately I can't provide the sources.  nadir nominal focal is 146mm

Estimation Results for Nadir RGB Camera
6.3.1 Specifications for output image
Value
Nominal Focal Length [mm] 146.000
Pixel size [mm] 0.00376

i will test separate chunk for each camera and try to assemble them after densecloud

Paulo

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Re: Alignment Error on aerial photogrammetry
« Reply #11 on: September 28, 2022, 05:20:13 PM »
I would definitely uncheck Fixed parameters in Camera Calibration, do Optimization and see if point cloud is better
Best Regards,
Paul Pelletier,
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JMR

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Re: Alignment Error on aerial photogrammetry
« Reply #12 on: September 29, 2022, 02:43:19 AM »
... and i can't get tie point information to knwo wich photo generate this specific tie point...
If you can select a tie point you can filter photos pane "by points". This will tell you the photos it comes from.