How to update maps in mods. 1.18

I wanted to make a mod that can update maps automatically. I looked up the nbt data of maps and discovered how to edit them. But I still don't know how to update them. Do I have to do that I check the highest block for each map pixel to update it or is there another way. You don't have to show me how to do it automatically, I just want to know how to do it once. I can make the auto part myself.