Some questions about u-net ： image and mask dataset

[xpji]

hi. I learned a lot from your videos, thank you for your selfless sharing.

In the u-net-related videos, I found that some training data includes image data and corresponding mask data.

Excuse me, if I want to download the satellite radar data by myself to perform a similar process, do I need to make the corresponding mask data for the radar image? If necessary, how should it be produced in general? Can you make a tutorial to explain it? Thanks