I would like to create one polygon including others polygons that has an
ID < 16 .
EDIT : I do not want to get a multipart polygon, but a singlepart polygon and fill the spaces in between.
Probably not a good idea, but polygons being always alligned by ascendant numbering ( 1 - 2 - 3 - 4 - ...) , a logics could be to join polygon ID 1 to the polygon ID 2, then the polygon ID 2 to the polygon ID 3, etc. by joinning the closest corners to the next ID polygon.
I've no idea how to accomplish this task, is there a way to automatize it?
EDIT : the aim is to have only one polygon at the end