Because Idrisi currently lacks capability to read GEOTIFF files directly, the documentation recommends converting .TIF files to .BMP first (e.g. using Image Alchemy or Corel Photo-Paint), importing the .BMP files using BMPIDRIS. WARNING: Although the projection and datum may be read from the .FGD file, the ellipsoid may not be correctly reported. For example, O35113G7.FGD reports ‘GRS 1980’ but is actually ‘Clarke 1866’. Thus the appropriate parameter file is US27TM12 rather than US83TM12. The program FRAME.EXE, executable from the MS-DOS prompt, reads the .FGD metadata file of a DRG image and writes out a vector file representing the map area in lat/long. For example: Use INITIAL to create an image from the DRG with a value of 0. Then use POLYRAS to add the vector file data to the image. Because the polygon’s value is set to 1 and the INITIAL image is set to 0, the result is a mask that may be multiplied against the DRG image to zero out the margin area. Some .FGD files contain bogus referencing information (I’ve noticed this with some Alaska quads). If this is the case, or if you don’t have access to the .FGD file, REDOCW.EXE will fix the .DOC file using the .TFW file. Source.