Q: Vectorizate a rectangle of the base map twice. One is to draw the two adjacent sides at once, and convert the line to region. But you get two triangles with the rectangle diagonal. How to get the complete rectangular?

A: The line to region is to connect the start and end point of the line object to the region object, and it does not deal with the topological relation of other line objects. If you want to get a complete rectangle, you should use the function of building region topologically by the line dataset.