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FUB/WeW processor images
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FUB/WeW processor images
3/15/12 1:52 PM
Hello!

I could really use some help with FUB/WeW images. The problem is that optically active substances have logaritmic values, but I will need the concentrations in right units, like mg/m3 etc. In order to have them I have to compute new bands (using Create Band by Band Math tool). That part is clear to me. The question is releted to this expression that I need to insert into Band Math Expression Editor window. Which is the right function in this case??? I have tried two of them, but the results are either too high or quite low (and homogenous), especially with chl_a. The functions I used were first exp(@) and then I tried pow(10,@). These seem to be unsuitable because of their greate under- or overestimation.

I will be very thankful if someone could help me with this question!

All the best!
Evelin
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RE: FUB/WeW processor images
3/21/12 6:04 PM as a reply to Evelin Kangro.
Dear Evelin,

depending on your use case, you don't have to care about scaling. When you deal with image data in VISAT, you already get geophysical data, which already takes the scaling into account. Therefore your values are quite wrong when you scale them again ;-)
May I ask what your specific use case is?

Best regards,
Thomas
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RE: FUB/WeW processor images
3/30/12 10:16 PM as a reply to Thomas Storm.
Hello, Thomas!

I appreciate your response!! I understand that I don´t need to worry about scaling the geophysical data. In my case I use these FUB/WeW pictures for match-ups, which means that I have in situ measurements that have concentration units mg3/l (chl_a), g/l (tsm) and 1/m (CDOM) and I need to compare them with values I get from satellite pictures. But how to do that with FUB pictures, if pin values are logaritmic?? Then I should compute new bands??

Best wishes,
Evelin
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RE: FUB/WeW processor images
4/4/12 10:35 AM as a reply to Evelin Kangro.
Hi Evelin,

ok, it seems that you need to scale your logarithmic values. Do you know what logarithm was used for scaling them? Since you failed with the expressions you mentioned in your first post, perhaps try using pow(2,@), assuming a 2-logarithm was used.

Best regards,
Thomas
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RE: FUB/WeW processor images
4/28/12 8:48 AM as a reply to Thomas Storm.
Hi, Thomas!

Thank You very much for replying again! I got the assurance that it is better if I use this forumula. Now I have the results and with chl-a it works quite well. Thank You!

I also tried to find these NN training ranges of optically active substances for FUB processor, but I didn´t find anything useful. I got the ranges for
Boreal, C2R, Eutrophic but not for FUB/WeW.

I really could use these values!

All the best!
Evelin
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RE: FUB/WeW processor images
5/7/12 2:07 PM as a reply to Evelin Kangro.
Hi Evelin,

Thank You very much for replying again! I got the assurance that it is better if I use this forumula. Now I have the results and with chl-a it works quite well. Thank You!


great! I am glad to hear that.

As to your other question: since the FUB/Wew processor is a third-party-module not developed by BC but by FUB, I'd suggest you ask the original developer. His mail address is michael.schaale@wew.fu-berlin.de.

Best regards,
Thomas
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