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Sun irradiance in red

Hello,

We are taking UAV images with rededge and the sunlight sensor. For images of some dates, we have the irradiance information and for some we do not (It might be that we are getting the irradiance tag after updating rededge firmware). I read a post where the same happened with sequoia and he was asked to tag the images with the irradiance information manually by  Xmp.Camera.IrradianceRelativeRotation  173, 0, 0. I extracted the metadata of the dates where sun irradiance calibration couldn’t be performed with exiftool, and saw that the information was not present in the metadata

Will the relative rotation parameter be same for the rededge camera as well? I want to tag the images manually.

Thanks,

Momtanu

Hey Lav,

I am commenting because, I also want know if it is possible to manually extract sun irradiance information prior to processing.

Hi,

@ Lav

The Xmp.Camera.IrradianceRelativeRotation is used for sun angle correction (to compute its angle with respect to the sun and adjust for the sun’s intensity). Since for the moment, we do not perform the sun angle corrections with the Rededge adding this tag will not be of a great impact on the results. 

On the other hand for performing sun irradiance you will need to make sure that you have the tags listed in the article: https://support.pix4d.com/hc/en-us/articles/206434245-Camera-XMP-Specification#gsc.tab=0 

@ Selim I am not sure if I correctly understood the query. 

The only way I see you could do this manually is to read the exif of the imagery and copy/read the tags containing the information from there.

As per the software, Pix4D mapper does not have as an output radiometrically corrected images. The images are radiometrically corrected during step 3 and from them the reflectance map is created. The final output will be the reflectance map itself and not the corrected images or any other files with the radiometric information.

Cheers,

Ina

Hey Ina,

Thanks for your comment. I am able to to extract the exif data prior to processing. But I am not sure what kind of information that I am looking for in order to compute a table that includes the reflectance values before processing. What I am trying to figure out is that, is it possible to get the reflectance value information from the images before processing? Is there a specific formula that I can execute in order to get that ? Ideally I would like to remove the images that has skewed reflectance values prior to processing. Could you please explain  more how can I  read the exif of the imagery specific to the reflectance values? Thank you.

Hi Selim,

From our side we do not have such workflow. But what I suggest is to take a look at Parrot forum, I saw they were discussing there something similar: 

http://forum.developer.parrot.com/t/details-of-irradiance-list-tag-for-sunshine-sensor-in-exif-data-of-sequoia/5261 

Cheers,

Ina

 

Hey Ina,

I will look into that link. Thank you.

Hey Lav,

i used to have the same problem, but now i found the solution.

You should create a new namespace called “Xmp.Camera.IrradianceRelativeRotation” using exiftool.

then run the following code to set its value to 173, 0, 0 :

c:\>exiftool -config “c:\xxxxx\exiftool.config” -XMP-Camera:IrradianceRelatveRotation=“173, 0, 0” C:\xxxxxx*.tif

Cheers!

Siline

 

Hey Siline,

Can you get the reflectance values from the the raw images with that script? Thanks.

Hi Selim,

I think so,

Hey Siline, 

Thank you for the information. I will definitely look into that.