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Messages - Arie

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61
General / Re: Thermal Orthomosaic Workflow
« on: May 15, 2020, 03:19:04 PM »
It's been awhile since I last worked with thermal images but I remember having to input some camera calibration values, such as sensor size, pixel size etc., before running the alignment. If I remember correctly, the pixel size wasn't square but varied between length and height.
Good luck!

62
General / Re: Help filling a hole in my ortho
« on: May 15, 2020, 03:13:20 PM »
Hi,
just as a quick thought: Why don't you just use the "Fill nodata" tool from the processing toolbox to interpolate the hole in QGIS?
Cheers.

63
General / Re: Bad render in Blender, not like agisoft...
« on: May 11, 2020, 09:11:48 AM »
Hi Dyst,
could it be that the main difference between the two is that Agisoft uses a shadeless approach for displaying textured meshes while in Blender you see more of the surfaces geometry due to lighting?

64
General / Re: Bad Stitching - What causes this?
« on: December 28, 2019, 02:42:05 AM »
Hey ashalota,
why are you dividing the flight lines into separate chunks if you have enough overlap between the lines and GPS tags? What do you mean by "varying long flight-lines"?

In general, I would recommend to align all the images in one chunk. Since your images have GPS coordinates, they should be roughly pre-aligned, reducing the processing time quite a bit in comparision to deactivating preselection altogether ( make sure to select Reference preselection in the alignment dialog).
For creating a dense cloud/ mesh and DEM/ Orthomosaic you can use the "split in chunks" script (https://github.com/agisoft-llc/metashape-scripts/blob/master/src/split_in_chunks_dialog.py). This reduces the memory required for processing and will ensure a seamless transition between the separate orthoimages.

Are you using a RTK-GNSS? And don't you have ground control points?


65
General / Re: 3D modeling of am object from a CT scan
« on: December 28, 2019, 02:01:56 AM »
Hey oritik,
Alexey is right, the images are definitely not suitable for typical photogrammetric processing pipelines based on SFM/MVS.
Creating 3D-models from CT-scans is actually fairly easy and there are a lot of different programs for this. I personally had some good experience using 3D Slicer, which is free and open source.
Do you have the original DICOM files? That's the standardized file format for CT scans, using these makes processing even more straight-forward.
Drop me a line in case you need more tips.
Cheers!

66
General / Re: Lens question
« on: April 17, 2019, 12:14:46 PM »
Hi pbourke,
the focal length of a lens can change when adjusting the focus. This is a well-known effect named "focus breathing".

In general, I usually use only manual focus, i.e. I stay at a constant distance to the object-of-interest. If I need some additional close-up shots, where I am required to refocus, I create a second calibration group for the images with the adjusted focus in Agisoft to compensate for the change in focal length.

Hope that helps.
All the best,
Arie.

67
General / Re: Investigating Alignment Parameters
« on: December 19, 2017, 11:55:01 AM »
Additonally, wouldn't the electronic shutter also influence the results regarding the reprojection error (i.e. rolling shutter effect)?

68
General / Re: Method For Masking Out Sharp Pixels?
« on: November 14, 2016, 09:59:39 AM »
Hi DTFrontMan,
when dealing with depth-of-field issues I often use Photoshops CCs feature "Select Focus Area". It automatically selects unsharp portions of the image, which can be used as a mask for texturing in Photoscan.
Most of the time, this works quite great!
Cheers.
Arie.

69
General / Re: Using Global (ASTERDEM) as ground control points?
« on: August 10, 2016, 07:19:38 PM »
Quick answer: Not, it won't be valid.  :P

This is mainly due to the accuracy and resolution of AsterDEM (and probably wordDEM too). According to the specs, the AsterDEM has a accuracy in the range of several meters. http://www.jspacesystems.or.jp/ersdac/GDEM/ver2Validation/Summary_GDEM2_validation_report_final.pdf

And if you take a critical look at the accuracy assessment, they compare it to SRTM. These datasets do not nearly achieve the same resolution and accuracy as aerial imagery.

You should rather try to find out why your DEM is concave/ convex. 10 minutes of googling will help you out ;)
Cheers.

70
Hi,
now that DNG support has been added, I was wondering where exactly the benefits are. I'd guess processing utilises the full bit depth of the input images, so it should also be possible to export textures as 16-bit imagery.

But I've noticed, that no external corrections, such as vignetting removal, noise reduction, white balance etc., are being applied when viewing the images in PS. Might it be possible to support the output as DNG (similiar to Lightrooms DNG output after panorama stitching) to do noise reduction, WB etc. in post?

Any other advantages of using DNG in comparision to 16-bitt TIFF except file size?

71
General / Re: Images acquired from high distance
« on: June 26, 2016, 01:57:44 PM »
I'd think, a baseline of 10-15 m for shooting at a distance of 1km is way too small. Additionally the 180 mm on a 1/2,3" sensor equals to a 1008 mm focal length on a full frame sensor.

I'm pretty sure you will not get decent results regardless the software you use.
Cheers.

72
General / Re: Spurious holes in mesh
« on: May 28, 2016, 01:49:44 PM »
You could also give cloudcompare a try. Its Poisson reconstruction plugin (http://www.cloudcompare.org/doc/wiki/index.php?title=Poisson_Surface_Reconstruction_%28plugin%29) is quite powerful, but finding the right parameters is important. Export the pointcloud as ply with normals, import to cloudcompare, mesh it and reimport to Agisoft for texturing.

Regarding the paremeters for the poisson reconstruction, setting the octree depth to 13 or 14 yields fairly high resoltuions meshes. The samples per node should be set higher than the default value for noisy pointclouds.

good luck.

73
General / Re: Some general questions about Photoscan
« on: April 27, 2016, 01:34:05 PM »
Hi,
1. PDF files are not really optimized for displaying large amounts of points/polygons. Therefore a reduction usually is necessary. The red color is a indicator for a selection; so when your mesh/ points turn red it means you selected it.

2. The accuracy of the pointcloud is dependend on quite a few different factors. In lectures, I usually divide them into internal and external influences: Internal being everything involving the camera. To name a few, you have sensor noise (somewhat related to pixel pitch size), lens distortion, image sharpness (AA-filter, bayer pattern vs. monochrome, lens quality), depth-of-field vs. diffraction etc.
External factors would be things like image overlap, the type of object reflectance (diffus, specular, etc.), texture and structure of the surface, ground-sampling-distance etc.

3. Not quite sure what you mean with viewing point coordinates. AFAIK you can't pick a single point and view it's coordinate. You can do that with free software such as Cloudcompare.

4. Well, you can decide the geometric resolution of the orthoimage- so if you know a pixel in your original image has a GSD of 1cm, just set 1x1cm in the output tab.

Hope that helped-
Cheers.

74
General / Re: New FF camera, but have some questions..
« on: April 04, 2016, 05:59:45 PM »
The amount of megapixel determine how much details can be captured with a single shot. Of course you can get the same amount of detail with a lower resolution camera, but you would have to take more pictures while being closer to the object of interest.
Furthermore, with more megapixels (smaller pixel pitch), lens defects show more clearly- this means, better lens quality is needed for optimal utilization of the increased resolution. For example, unsharp corners might not show on a 10 mp sensor, while being clearly visible on a 36mp sensor.

In general, I would recommend to spend at least as much on the lenses as on the camera body. The value of the camera body decreases way more rapidly than lenses do.

The 35mm f2.8 is a lovely, tiny lens, which has a very good image quality. Also, what stihl said.
Cheers!

75
General / Re: 4K video instead of image files?
« on: April 04, 2016, 05:48:26 PM »
AFAIK, one cannot import video files to Agisoft. There is a bunch of software out there, which can extract single frames in an defined time intervall (for example, ffmpeg).
In general, video footage is not the best option due to the rolling shutter effect, which most cameras exhibit. Since this type of distortion cannot be corrected, it leads to worse results.

Cheers.


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