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Topics - monviso

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1
General / Thermal images pixel size
« on: November 10, 2021, 07:03:28 PM »
Hi all,

just a quick question. I see from here https://agisoft.freshdesk.com/support/solutions/articles/31000158942-thermal-imagery-processing, I see that is suggested for thermal images specify pixel size and focal length (mm) of the camera and set as fixed parameters f (I guess its dimension is in pixels). I have two question:
I-what is the rationale of that?
II- To my knowledge pixel size is computed as 1/FocalPlaneXResolution and 1\FocalPlaneYResolution, again what is the rational of that? For my camera it gives 0.0919118 x 0.11489. But if I compute pixel size simply by FocalPlaneXResolution/Xresolution and FocalPlaneYResolution/Yresolution my pixel size would be 0.017x0.017. Does this make any significative difference?

Many thanks!


2
General / effect of accuracy on GDS in sparse and dense cloud
« on: October 22, 2021, 06:13:09 PM »
Hi all, I need an information (very basic probably). I know that if I process my images in low accuracy I downscale of a factor of 1:8 (i.e., if my GSD=10 cm than I will have GSD= 80 cm) My question is: if I process images in low accuracy both in the sparse and dense cloud step do I apply this factor two times? example: my GSD is 10 cm, I calculate sparse cloud in low accuracy than I have a GSD of 80 cm. If I further process the dense cloud in low accuracy, my GSD will be then  640cm? or the factor still apply to the original resolution (i.e. my final GSD=160cm )?


Many Thanks

3
Feature Requests / export orthophotos issue - amended
« on: March 04, 2021, 02:36:35 AM »
Hi everyone,

I need to export the orthophotos on which my orthomosaic is built. I need to do so because I want to see how the value of the pixel vary from camera to camera using the tie points. The problem is that the values of the pixel range between -8 to 5 (are °C). So the background value is black or white (I guess 0 or 1) when I export as TIF, so values that easily can be confounded with the values of the pixels. Is there a way to customize the background values?
I am asking because when I import the orthophotos in R for the analysis it's almost impossible to distinguish between background value of the rotated tif and the real 0 or 1 value of the pixels. 

Thanks
Matteo

I need to amend the message:
I believe that the orthophoto I am exporting are not complete. It is probably my lack of knowledge, but I thought that they should be the original photos projected. Here attached a sample of the result I have (pixels value range -9.08 to 3.21). As you can see many areas of the orthophoto (but not in the background), have the value 0. I know that this is not true from the original images, so I guess they lack of some part. Why this happen?

Matteo

4
Feature Requests / details on projects "ancillary" files\folder
« on: February 26, 2021, 01:06:51 PM »
Hi all,

let me first say that some expression in this post can be inaccurate or wrong, but I am asking about quite obscure for me.. so apologise in advance.

I would like to know if somewhere I can find details on how projects build and save its ancillary files. With ancillary file I mean the folders and its content that are automatically created by metashape when we save a project. I see that the file folder contains many files and zipped folder. Is there a way to understand how they are organized? Specifically I would like to understand if the project once it is opened uses the original file to display the orthophotos or uses a copy of them placed in the ancillary filed (I guess in the zip folder). I am asking because I need to build different orthomosaics of the same set of images (calibrated thermal, .tiff, ~1000) but with different thermal calibration parameter (the alignment process of these images took me 4 days, more than 80 hours of computation!!), and thus I am trying to find a way to avoid the alignment step by substituting the new calibrated images in the ancillary folder of the project considering that they are the same image but with variation of temperature values that do not impact in any way the image itself.
Or, an alternative solution, is there a way to apply the tie points of the first orthomosaic to the new set of images?
Hope to have been clear.
Any solution is welcome
Matteo

5
Feature Requests / thermal images multi camera system process
« on: February 05, 2021, 11:21:09 AM »
Hi,
I am trying to process with the multicamera system two folder containing thermal images and RGB from XT2 camera. If I ran the process using the original r-jpg and rbg together all seems to work (I have in the photos window the two images coupled one small and one large). Does anyone know what metadata allow the two images to be considered "from the same camera"?
I have wrote a script in R to convert r-jpg into absolute temperature tif raster and edit its metadata in order to have the necessary information (e.g. GPS position) to import the tif in metashape but when I try to process them together with rgb, I can't see them coupled. Any help is really appreciated. Thanks

6
Feature Requests / Tie point coordinates accuracy
« on: February 05, 2021, 01:31:53 AM »
Hi everybody, I am new to the forum.

I have a question regarding tie points. My UAVs horizontal accuracy is +-1mt ( I would assume that the coordinates of the centre of each image have the same uncertainty). In the field I have set a grid of GCPs geolocated with an accuracy of 0.1mt. In my workflow in Metashape, I align the images and after I import my GCPs (text file) and I correct the position of the point cloud. I am interested into the position of tie points, so my question is: after the use of GCPs correction, can I assume an accuracy of the tie points coordinates of 0.1mt?
Thanks
Matteo

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