It sounds like your TIFF files have associated world files (.TFW) that contain the coordinates of the map tie point (usually the upper left corner), but no projection information. This is not uncommon. ENVI attempts to read map information from the TIFF itself first, then tries the world file. Since the world file doesn't have projection information, it prompts you to enter that information. To nudge you in the right direction, you could try the following in a batch program: - call envi_open_external_file with the tiff keyword set and pass it one of your tiff files - call envi_file_query to obtain the number of samples, lines, and bands in your file, along with interleave, data type, and file type - call read_ascii to retrieve the tie point information from the world file - call envi_map_info_create to generate the map information you need. The projection and datum shouldn't change, so those can be hard-coded. You can pass in the pixel size and tie point pixel coordinates from the values stored in the world file - call envi_setup_head to create an ENVI header file for your tiff. You'll have to provide the number of samples, lines, bands, interleave, data type, file type, and map information. Do this for all of your tiffs and then, when you need to open one of them in ENVI, try File->Open Image File instead of Open External File->GeoTIFF. The former will check for an ENVI header file with map information for the tiff before attempting to read map information from the file itself or the world file. The tiff will still open as it should since the file type is specified in the header, but ENVI will pull the map information it needs from the header so you shouldn't receive a prompt. If you would like more detailed assistance with putting this type of program together, you can submit a technical support request to support@ittvis.com (as long as your maintenance contract is current) and we'd be happy to help.