I have been trying to perform sub-pixel classification using ERDAS IMAGINE. However, I am unable to proceed due to series of errors at the very beginning. To start with, I have completed quality assurance and artifact removal steps successfully. Next step, preprocessing is producing warning message saying the input contains only one primary class and it does not produce .aasap file. However, sometimes the job list shows the process to be complete, but without generating a .aasap file. I cannot do the next step, environmental correction, without .corenv file and even that is not getting generated. I have converted my input file to uint8 format as required. Kindly suggest what could be done. Also, I am not aware of generating signature set manually for subpixel classification. It would be greatly helpful if someone can direct me to the correct methodology.