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Author Topic: Processing of R-JPEG  (Read 1792 times)

UAVflyer

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Processing of R-JPEG
« on: February 17, 2022, 02:29:00 PM »
Hello,

since Metashape Version 1.8 R-JPEG are supported:

I generated an Orthomosaic based on Zenmuse XT2 camera (RGB and IR) and the resulting Orthomosaic based on the index values of Band 4 has values ranging from 29285 to 32441.
Do I have to calibrate this sensor values to extract °C temperature, or is this only *1000? I guess the calibration might have happenend within Metashape automatically if R-JPEGs are supported?

Thank you for your advice,

UAVflyer


Paulo

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Re: Processing of R-JPEG
« Reply #1 on: February 17, 2022, 02:40:28 PM »
Hello UAVFlyer,

I think that formula for converting to °C would be:
Code: [Select]
B4*0.01 - 273.15
which would give you a range of 19.7 to 51.26 in °C
« Last Edit: February 17, 2022, 03:14:09 PM by Paulo »
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Paul Pelletier,
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UAVflyer

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Re: Processing of R-JPEG
« Reply #2 on: February 17, 2022, 04:33:48 PM »
Thank you very much for your reply. Is this specified somewhere? I found a formula based on FLIR conversion stating B4*0.04-273, however that lead to unrealistic values.

Paulo

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Re: Processing of R-JPEG
« Reply #3 on: February 17, 2022, 08:47:02 PM »
You are correct on this. The formula I came to is rather empirical as it gives realistic values but does suppose that somehow the R Jpeg vaues have 4 times beter resolution than original. So maybe this should be confirmed by DJI....
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Paul Pelletier,
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Alexey Pasumansky

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Re: Processing of R-JPEG
« Reply #4 on: February 18, 2022, 11:36:12 AM »
I think that MicaSense Altum uses the same formula for C temperature extraction from LWIR band:
https://support.micasense.com/hc/en-us/articles/360022446473

Quote
output units are centi-Kelvin. In order to convert the temperature values from centi-Kelvin to an unit that is easier to interpret, you will need to divide the output by 100 (which gives you Kelvin), and then subtract 273.15 to convert to Celsius.
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Alexey Pasumansky,
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