The method is as follows:

First, vectorize in GE. Vectorization method, in GE, create a new polygon, as shown below? In GE, when the mouse becomes a Tian Zi box, hold down the left mouse button and drag it into the shape of the study area.

After that, you can also drag the boundary with the mouse to modify it.

see:/html/GIS/ArcGIS/2111216/12622.html for details.