Removing unnecessary vertices ?

When you have in a complicated mesh (e.g. landscape) a flat part that contains many unnecessary vertices (because they’re defining that flat surface), is there a way to simplify this part ?
Or do you have to delete these vertices and rebuild the faces ?
Thanks for help

You can try the decimator in the edit window, but IMO I’d delete the vertices and redo the face.


Or if you want to be lazy, delete all the vertices, Shift-F to Fill (with the border of the vertices deleted selected), then Alt-F a few times to Beauty Fill, and then J to Convert to Quads… It’s faster than rebuilding the faces manually.