Page 1 of 1

Selecting reflectance math band

Posted: Mon May 23, 2022 2:32 pm America/New_York
Hello,
I want to improve the Chl a concentration data in the Southern Ocean, specifically Drake Passage.
I found this algorithm Chl=exp10(0.3205-2.9139R+8.7428R2-16.1811R3+9.0051R4)
R=log10(Rrs(443/555)>Rrs(490/555)>Rrs(510/555))
for Globcolour data. In this paper https://doi.org/10.1002/jgrc.20270

I trying to use math band to select greatest reflectance proportion, however my programing knowledge is very limited
Tried something like: if log10(443/555)>log10(490/555)>log10(510/555) then log10(443/555) else log10(490/555)>log10(510/555).

Or maybe I can do it separately and see which one is greatest.
Some one can give me a hint?
Thanks,

Re: Selecting reflectance math band

Posted: Tue May 24, 2022 4:49 pm America/New_York
The BandMath expression to replicate the Chl GlobColour equation 6 of the paper you reference would be:

First create band named R:

Code: Select all

``````if (log10(Rrs_443/Rrs_555) > log10(Rrs_490/Rrs_555)
and log10(Rrs_443/Rrs_555) > log10(Rrs_510/Rrs_555))
then
log10(Rrs_443/Rrs_555)
else
(
if (log10(Rrs_490/Rrs_555) > log10(Rrs_510/Rrs_555))
then
log10(Rrs_490/Rrs_555)
else
log10(Rrs_510/Rrs_555)
)
``````
Then apply the coefficients to create the Chl band:

Code: Select all

``````exp10(0.3205
-2.9139 * R
+ 8.7428 * pow(R,2)
-16.1811 * pow(R,3)
+ 9.0051 *pow(R,4)) ``````

Re: Selecting reflectance math band

Posted: Tue May 24, 2022 9:01 pm America/New_York
Thanks a lot!