Details of Irradiance List tag for Sunshine sensor in exif data of Sequoia


#65

@seanmcleod, I am new to the sequoia system so please forgive me if this is obvious. For one image, I see there are 9 lines of output. Can you elaborate on what each line is referring to for the given image?


#66

The Sequoia seems to record those values at roughly 5Hz and so those 9 lines are the last 9 readings from the time of the previous image that was captured up until the capture of the image that you see the output from.


#67

Got it. Thanks! I see that number 9 does not seem to be a magic number… I am playing around with the example multispectral dataset from the Pix4D support site until we do an actual data collection. Some have 9 readings, some have 4, etc. Is it a good assumption to take the final reading as the one relevant to a specific image?


#68

You can see how frequently the readings are taken by looking at the timestamps. I’m assuming Parrot include multiple instead of just the last reading before the image to allow you to choose whether you possibly want to take a simple average, or a weighted average or even just the latest one.


#69

I am working with some older Sequoia images captured with firmware version 1.0.2 from back in summer 2016. I have problems decoding the Irradiance List tag for Sunshine sensor in these images. I use the python code shared by Seanmcleod in this threat and it works perfectly with newer images, but not with the old ones. Can anyone help?
I have shared an image.IMG_160817_181016_0062_GRE.TIF.zip (1.5 MB)


#70

Hi @rasmus, sorry for the delay.

Prior to version 1.1.0 (long time before this was documented publicly) the format did not include gain and integration time, which were fixed to gain index 0 instead of gain index 1 and 100ms (struct.unpack format was ‘Q 2H 2f’).

Best,


#71

from here we can know to calculate the sunshine irradiance as following:
29
we need know parameters: k–coefficient of proportionality, v–CH0 count, g–relative gain factor and t --the exposure time of sunshine sensor.
In order to program on that, I’ll analysis each parameter.
1)relative gain factor : only depends on device manufacturing, therefore it can be computed beforehand and just stored in the form of array for each gain mode. Following array can be initialized for the example given above:
gain_factor = [11/330, 1, 3990/330]
gain mode is 0,1,2 and response to gain_factor, which could be got from Xmp.Camera.IrradianceList, usually is 1.
2) exposure time: can be got from Xmp.Camera.IrradianceList ,for example 100 (what unit is it?)
3) CH0 count : can be got from Xmp.Camera.IrradianceList , for example 2738
4) coefficient of proportionality: is always ignored

what I understand is right or wrong?
and after decode , Xmp.Camera.IrradianceList has seven line, which line is the right parameter?

Xmp.Camera.IrradianceList:

(1490099095, 2840, 724, 1, 100, -46.500343322753906, 5.559251308441162, -3.707690715789795)
(1490298926, 2844, 725, 1, 100, -46.19866943359375, 6.361606597900391, -2.2823097705841064)
(1490499056, 2823, 719, 1, 100, -46.3399543762207, 6.417032241821289, -4.0200066566467285)
(1490701351, 2789, 711, 1, 100, -46.733863830566406, 6.262904644012451, -4.572281360626221)
(1490898867, 2738, 698, 1, 100, -46.75264358520508, 5.657809257507324, -1.965978980064392)
(1491096192, 2710, 690, 1, 100, -46.70916748046875, 6.442657947540283, -2.0115420818328857)
(1491298007, 2701, 688, 1, 100, -47.1677131652832, 6.861001968383789, -3.4753665924072266)