How can I get 'free2.grd' and GeoModel file

[Echo-cwb]

Dear author:
When I run your code, it gets error at "control0=pygmt.select(region="free2.grd",data=ship_depth)" part, as I show in the picture. I wonder how I can fix it, and whether it is needed to get 'free2.grd' or GeoModel file. Thanks a lot!

[yangleir]

你好，这里使用了GMT的一个select命令，仅调用了nc文件的边界。这里可以使用很多方法进行替换，比如直接使用region=reg。