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.
BMPIDRIS x 2 i01 i01 drgOnce the image is imported, its georeferencing information must be entered. The program REDOC.EXE, executable from the MS-DOS prompt, reads the .FGD metadata file of a DRG image and enters the appropriate information into the .DOC file, optionally applying a y-shift to the coordinates. For example:
redoc i01 i01REDOC only affects the title, min. X, max. X, min. Y, max. Y, and resolution entries of the documentation file; other data (e.g. ref. system) will need to be entered manually.
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.
WARNING: Avoid packbit compression during this process, as it may lead to image shifting.
1) Create a lat/long vector file representing the map area.
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:
frame i01 i01 [I01.VEC] 1 5 -113.875000 35.750000 -113.875000 35.875000 -113.750000 35.875000 -113.750000 35.750000 -113.875000 35.750000 0 0 [I01.DVC] file title : Frame file id type : integer file type : ascii object type : line ref. system : latlon27 ref. units : deg unit dist. : 1.0000000 min. X : -113.875000 max. X : -113.750000 min. Y : 35.750000 max. Y : 35.875000 pos'n error : unknown resolution : unknownNote that the default ref. system is LATLONG. In the above example, the DRG uses the Clarke 1866 spheroid; thus the .DVC file has been edited to refer to a parameter file called LATLON27:
[LATLON27.REF] ref. system : Geodetic Coordinates (Latitide/Longitude) projection : none datum : NAD27 delta WGS84 : -8 160 176 ellipsoid : Clarke 1866 major s-ax : 6378206.40 minor s-ax : 6356583.80 origin long : 0 origin lat : 0 origin X : 0 origin Y : 0 scale fac : 1.0 units : deg parameters : 02) Project the vector file to the DRG's reference system.
PROJECT x 2 i01 latlon27 i01p us27tm123) Convert the vector file to a raster mask and overlay the DRG image.
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.
INITIAL x i01v 3 1 0 1 i01 unspecified POLYRAS x i01p i01v OVERLAY x 3 i01 i01v i01ov4) CONCAT the resulting images using the transparent option.
CONCAT x # 4 drg 2 i01ov i02ov i03ov i04ovWARNING: If the first image in the list is not leftmost AND topmost, the geopositioning of the output image will be thrown off. The program REPOS.EXE, executable from the MS-DOS prompt, reads the document files of the input and output images and corrects the positioning of the output image. For example:
REPOS drg i01ov i02ov i03ov i04ovThis bug has been fixed. You can download the latest Idrisi update at: http://www.clarklabs.org/13dnlds/13dnlds.htm
CONCAT x # 4 drgv 2 i01v i02v i03v i04v(See WARNING above.)
6) Use RECLASS to swap the 0 and 1 values.
RECLASS x i drgv drgr 2 0 1 2 1 0 1 -99997) Use OVERLAY with the Cover option to create the final image.
OVERLAY x 7 drgr drg drgw
REDOC: "8.4 TITLE:" "1.2.3 SUPPLEMENTAL INFORMATION:" "3.4.2 ROW COUNT:" "3.4.3 COLUMN COUNT:" "184.108.40.206.2.1 ABSCISSA RESOLUTION:" FRAME: "220.127.116.11 WEST BOUNDING COORDINATE:" "18.104.22.168 EAST BOUNDING COORDINATE:" "22.214.171.124 NORTH BOUNDING COORDINATE:" "126.96.36.199 SOUTH BOUNDING COORDINATE:"If you edit the .FGD file to match the above key phrases, the programs should work properly.
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.