McIDAS Learning Guide
Version 2006

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Real-time Data Access - Satellite Imagery

In the first part of this exercise, you will access real-time satellite imagery and review many of the associated McIDAS commands. You will use these commands to display real-time satellite imagery, as well as list information about the data. A good review of satellite data and McIDAS AREA files can be found in the Basic Concepts section of the Satellite Imagery chapter.

Displaying Satellite Data

The DSINFO and IMGLIST commands list information about the images you have access to. Once located, you can display the images using the IMGDISP command. You can display images one at a time or in a sequence. An entire set of images can be loaded chronologically using one IMGDISP command.
  1. List all datasets of type IMAGE in your routing table.
    Type:  DSINFO IMAGE
    This will list all of the IMAGE datasets that you have access to in your routing table.

  2. Erase graphics frames 1 through 4.
    Type:  ERASE G 1 4
  3. List the area directories for the four most recent GOES-8 images.
    Type:  IMGLIST EASTS/CONUS.-3
     Image file directory listing for:EASTS/CONUS
  Pos Satellite/         Date       Time      Center   Band(s)
      sensor                                 Lat  Lon
  --- -------------  ------------  --------  ---- ---- ------------
   16  G-12 IMG       7 AUG 03219  23:15:00    14   72 1-4,6
   12  G-12 IMG       7 AUG 03219  23:02:00    32   87 1-4,6
   11  G-12 IMG       7 AUG 03219  22:45:00    14   72 1-4,6
   15  G-12 IMG       7 AUG 03219  22:32:00    32   87 1-4,6
 IMGLIST: done
  4. Display the four most recent GOES-8 IR images chronologically by using the ALL keyword. Place the images in frames 1 through 4 and center them on Miami.
    Type:  IMGDISP EASTS/CONUS BAND=4 ALL=1 4 STA=MIA
    Because real-time satellite data is updated often, it is possible to view an image that has not yet been fully ingested by the server. If you attempt to access the most recent image in a dataset, you may get unexpected results. This may be a partially black image, or for GOES images, an image that you can see tracking across the screen. If you can see the most recent image slowly filling up the image frame, you are actually watching the data as it comes in line-by-line from the satellite. This is normal behavior.

  5. Set the loop bounds to loop through frames 1 through 4 and loop the frames. Stop the looping when you are finished looking at the images.
    Type:  LB 1 4
    Press:  Alt L
    Press:  Alt L

Listing Image Information

When you display an image on a frame, McIDAS creates a frame directory for the image which lists the frame number, sensor source, date, image time, band number, image coordinates, magnification factors, and ADDE dataset name and file position number. The FRMLIST command lists the frame directory.

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 be invoked with its default parameters by pressing Alt-D.

Even though the data is not located on your local machine, but rather on some remote server, you can still access information about the data.

  1. List the frame directory for all of the images in frames 1 through 4.
    Type:  FRMLIST 1 4
    Information about the frame number, sensor source, band, date, time, and ADDE dataset/position number is displayed for each image. 
       Frame   Satellite                                                                  
  [panel]  Sensor       Band     Date       Time   Data Source                        
 --------- ------------ ---- ------------ -------- -----------------------------      
      1[1] G-12 IMG      4   07 Aug 03219 22:32:00 EASTS/CONUS.15                    
      2[1] G-12 IMG      4   07 Aug 03219 22:45:00 EASTS/CONUS.11                     
      3[1] G-12 IMG      4   07 Aug 03219 23:02:00 EASTS/CONUS.12                     
      4[1] G-12 IMG      4   07 Aug 03219 23:15:00 EASTS/CONUS.16
  2. List the area values for the element at the center of frame one .
    Type:  SF 1;PC C;IMGPROBE MODE=N
    Alternate method:
    Type:  SF 1;PC C
    Press:  Alt D
    The area number, area coordinates, image coordinates, raw, and brightness values are listed. Because this is an infrared image, the temperature and radiance values are also listed. 
    
      Image Name           Day      Nominal Time   Scan Time    Band
   ----------------      -------    ------------   ---------    ----
   EASTS/CONUS.15       7 Aug 03219   22:32:00      22:35:25      4
 
                         File     Nominal  Image     RAW     RAD     TEMP    BRIT 
        Lat/Lon      Line/Element  Line/Element               *       K
  25:46:26 / 80:17:59   585/ 1296    5177/14461      7776    43.476 248.20    164
  *   milliwatts/meter**2/steradian/(cm-1)

 IMGPROBE: Done

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