The result of chl is different

Please enter here to ask a question about any NASA Science related topics!
Post Reply
megasaputra8
Posts: 15
Joined: Sun Dec 27, 2020 10:57 pm America/New_York

The result of chl is different

by megasaputra8 » Tue Feb 02, 2021 4:12 am America/New_York

Hello guys,

I run l2gen from modis data. I extract chlor_a. I try to apply map projection after I extract into chlor_a. But, after I apply map projection, the result is different from image before I apply map projection.

The data is in : https://1drv.ms/u/s!AjXAWS5maHffhyu6DmUAGwxoJaJq?e=bDzBqR

Can someone explain, why is it different from image before I apply map projection?

Thank you.

Tags:

gnwiii
Posts: 612
Joined: Fri Jan 29, 2021 5:51 pm America/New_York
Answers: 1

The result of chl is different

by gnwiii » Tue Feb 02, 2021 8:44 am America/New_York

The mapping process can replicate pixels in some parts of the level-2 image and discard other pixels, so some differences are expected.  Please tell us more details of your workflow and what difference you are seeing.   In general, when posting this sort of report you need to supply enough detail so others can reproduce your work.

megasaputra8
Posts: 15
Joined: Sun Dec 27, 2020 10:57 pm America/New_York

The result of chl is different

by megasaputra8 » Tue Feb 02, 2021 6:35 pm America/New_York

The first I run l2gen to get chlor_a from data MODIS. I get the result is good. It means, there is chlor_a value.
The second, I apply map projection. I get the result is not good. The chlor_a value is only in northern area.

Finally, I test in other computer to get chlor_a and I apply map projection. Both the result is good (there is chlor_a value). May be the problem is the hardware specification of the computer. The computer that produce a bad chlor_a has a lower hardware specification.

Thank you.

gnwiii
Posts: 612
Joined: Fri Jan 29, 2021 5:51 pm America/New_York
Answers: 1

The result of chl is different

by gnwiii » Tue Feb 02, 2021 6:55 pm America/New_York

I assume you are using SeaDAS, which is  a Java application.  With Java, calculations aren't actually perfomed until the result is used.  On a slower system, it is quite possible to open a file with results of a calculation before the calculation has finished, resulting in partially blank images.

Post Reply