When using Adobe Photoshop CS3 to remove the redundant parts in the picture, we should use the method of matting:

1. First, open the source map, use Ctrl+J to copy the layer, and use the pen tool to tick off the part to be kept along the edge.

2.Ctrl+ Enter (turn the traced pen into a selection), click the third icon on the layer panel (add mask), and you can modify the details in the mask with a brush. This method is almost universal and is used for fine and accurate matting.