After several attempts, ArcMap is unable to create a signature file from training sample. I am working with an aerial image. Each time I attempt to create the signature file, it runs briefly, stops and after several minutes I get a failure notice. I suspected the image might be super-high res, but a right-click of the layer file is only 4k, which seems impossible given the detail of the image spreading over a county-wide are. Any suggestions would be appreciated. Thanks.