about 3 meter x 3 meter

[leizhu1989]

hello,thank for your information about paper. I still have a problem about how to crop a 3meter x 3meter form source image，I notice that when I use perspective map to crop 3x3 region from source image, I think it is rectangle but not square,also The paper says that extract 72x72 piece from source image ,is all like this for far or near in source image? but the perspective value is not the same, whether 72x72 piece can make sure the 3meter x3meter region in actual region from source image experss it