Dear Friends, I have used ISODATA unsupervised classification algorithm to classify Landsat5 TM data. I got the classified image, and can merge the classes using Overlay/classification option. But not able to perform accuracy assessment as there is no ROI associated with it. I also want to use this classification results as an input for supervised Maximum likelihood classification. I am using ENVI 4.5. Any help how to do this. Thanks PK