McIDAS Learning Guide
Version 2006

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Satellite Imagery - Listing Image Data

In this exercise, you will list image data by positioning the cursor on the image and entering the IMGPROBE command.

The IMGPROBE command lists data from the area represented on the image at the cursor center. It lists the area number, area coordinates, image coordinates, raw, brightness, and when present, temperature and radiance values. IMGPROBE can also be invoked by pressing Alt-D.

When the region parameter is specified as BOX, the IMGPROBE command lists the data from the area inside the cursor. By specifying different parameters, you can list raw, brightness, and when present, temperature and radiance values.

  1. Change your cursor to a smaller size with the CUR command, which is explained in more detail in the Graphics and the Cursor lesson.
    Type:  CUR 5 5
  2. Show the GOES-7 infrared image on frame 4 and position the cursor in the center of the frame. List the area values for the element at the cursor center by using the IMGPROBE command in the non-interactive mode.
    Type:  SF 4;PC C;IMGPROBE MODE=N
    Alternate method:
    Type:  SF 4;PC C
    Press:  Alt D
    The area number, area coordinates, image coordinates, raw, and brightness values are listed. The Nominal Time is the time the scan began, and the Scan Time is the time that pixel was scanned. Because this is an infrared image, the temperature and brightness values are also listed. 
         Image Name           Day      Nominal Time   Scan Time    Band
  ----------------      -------    ------------   ---------    ----
  GI4.1               13 Mar 93072   17:01:00      17:04:15      8

                        File     Nominal  Image     RAW     RAD     TEMP    BRIT  
       Lat/Lon      Line/Element  Line/Element               *      K             
 35:00:00 / 74:58:28   463/  993    2979/11566      5408    30.600  228.7    190  
 *   milliwatts/meter**2/steradian/(cm-1)
  3. List the brightness values for the area inside the cursor.
    Type:  PC C;IMGPROBE LIST BOX BRIT MODE=N

    Notice that the data value at the cursor center is the same value listed as with IMGPROBE.

  4. Show the GOES-7 visible image on frame 1 and list the values at the center of the cursor.
    Type:  SF 1
    Press:  Alt D
    Only raw and brightness values are listed when using visible data; whereas, temperature, radiance, raw and brightness values were listed for the infrared image in step 3.

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