Hello, may I ask where I can find the code for the FU Classification, I want to know the specific calculation process because I want to use the band calculation to calculate the FU of other sensors.

# Optical，thematic water processing

And How do I call a conditional function when I am in a band math, because I need to classify some of the band values involved in the operation?

You can find the code for the Forel-Ule Classification is in the Sentinel-3 Toolbox on GitHub,

These are the classes of main interest to you:

A conditional statement can be done with the band math as follows

```
condition ? true-statement : false-statement
```

or

```
if condition then true-statement false-statement
```

I’m not sure if it is possible to compute the FU Classification just by Band Maths. Because Band Maths doesn’t support loops, which are used in the code.

But you could do it in Python or in Java.

Thank you very much for your reply. I successfully calculated the hue_angle using the conditional statement in band math, and I converted it to FU through the lookup table. I don’t know how to implement it in snap. It is solved by using reclassification in arcmap.