McIDAS-X Learning Guide
Version 2020

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Satellite Imagery - Using Coordinate Systems

In this exercise, you will display the same image using different coordinate types. The coordinate system and location where the specified coordinates are positioned on the frame define the coordinate type. The three coordinate systems are: The two locations (PLACE) are:

The coordinate type is defined by a combination of the coordinate system keywords and location; for example, LINELE=6261 4745 I PLACE=ULEFT positions the (I) image coordinates (6261,4745) in the (ULEFT) upper-left corner.

The first exercise shows that the same image can be displayed using different coordinate types.

  1. Show and erase frame 1.
    Type:  SF 1;ERASE X 1
  2. Display the GOES-16 Full Disk Infrared image on frame 1 so the pixel having image coordinates (6501,5065) appears at the upper-left corner of the frame.
    Type:  IMGDISP G16FD.-1 1 LINELE=6501 5065 I PLACE=ULEFT BAND=13
    The combination of I for line/element type and PLACE=ULEFT places the specified image coordinates in the upper-left corner. Note in the on-line help for IMGDISP that the default for PLACE is ULEFT when LINELE is specified and therefore could be omitted from the command line above.

  3. Display the GOES-16 Full Disk Infrared image on frame 2 so that Puerto Escondido, Mexico, is at the center of the image frame.
    Type:  IMGDISP G16FD.-1 2 STATION=MMPS BAND=13;SF 2

    The STATION parameter places the earth coordinates for Puerto Escondido in the center of the frame, as shown below. When STATION or LATLON are used, the default for PLACE is CENTER.

  4. Display the GOES-16 Full Disk Infrared image on frame 3 so that file (area) coordinates (1865, 1586) appear in the center of the image frame.
    Type:  IMGDISP G16FD.-1 3 LINELE=1865 1586 F PLACE=CENTER BAND=13;SF 3
    The combination of F for coordinate system and PLACE=CENTER places the specified file (area) coordinates in the center of the image frame.

  5. Start and then stop the loop.
    Press:  LS 1-3;LS O 4-6
    Press:  Alt L
    Press:  Alt L
    All the images are the same, except they are displayed using different coordinate types.

  6. Show frame 2 and use the PC command to position the cursor in the center the frame. Then find the earth coordinates of Puerto Escondido. The PC command is discussed in more detail in the Graphics and the Cursor lesson.
    Type:  SF 2;PC C
    Press:  Alt E
    Command E lists the latitude and longitude of a pixel on a navigated frame in the format DD:MM:SS. It also lists the TV coordinates and image coordinates of the pixel. 
     Frame    Latitude    Longitude    Tvline    Tvelem    Line    Elem  
     2    15:52:12    097:05:00      240       320     7457    6341
Next you will display the same image three times, but change the location of the displayed image using different coordinate types.
  1. Erase frames 1 through 3 and show frame 1.
    Type:  ERASE I 1 3;SF 1
  2. Display the visible image from the ABI/CONUS dataset on frame 1 so that the earth coordinates 30° latitude and 89° longitude are centered in the frame. Then position the cursor at the center of the frame and verify that the earth coordinates are 30° latitude and 89° longitude.
    Type:  IMGDISP ABI/CONUS 1 LATLON=30 89 BAND=2
    Type:  PC C
    Press:  Alt E
    Notice that the center of the frame has a latitude of 30:00:07 and a longitude of 89:00:07.

  3. Display the image on frame 2 so that the image coordinates (1999, 2503) are centered in the frame and show frame 2. Then position the cursor in the center of the frame.
    Type:  IMGDISP ABI/CONUS 2 BAND=2 LINELE=1999 2503 I PLACE=CENTER;SF 2
    Type:  PC C
    Press:  Alt E
    Notice that the image coordinates (1999, 2503) are in the center of the frame.

  4. Display the image on frame 3 so that the file (area) coordinates (0,0) appear in the upper-left corner of the frame and show frame 3.
    Type:  IMGDISP ABI/CONUS 3 BAND=2 LINELE=0 0 MAG=-4;SF 3
  5. Change the dwell rate and then start and stop the loop. Notice how the image position changes.
    Type:  DR 10
    Press:  Alt L
    Press:  Alt L
Next, you will display a sequence of real time GOES-16 mid-level water vapor and infrared images using the same earth coordinates to compare them. Display the GOES water vapor images on the primary loop and the GOES infrared images on the opposite loop.
  1. Display the first GOES-16 0.5km water vapor image on frame 1, centering the image on earth coordinates 30° N and 75° W. Use the SF= keyword to automatically display the frame.
    Type:  IMGDISP G16FD.1 1 LATLON=30 75 BAND=9 SF=YES
  2. Display the next two GOES-16 water vapor images on frames 2 and 3, centering the images on coordinates 30° N and 75° W.
    Type:  IMGDISP G16FD.2 2 LATLON=30 75 BAND=9; IMGDISP G16FD.3 3 LATLON=30 75 BAND=9
  3. Display the three GOES-16 infrared images on frames opposite the GOES-16 visible images. The repeat factor (3) loads all three images with one IMGDISP command.
    Type:  SF 1;IMGDISP G16FD.1 OPP LATLON=30 75 BAND=13 REPEAT=3
    You are using the same coordinates, 30° N and 75° W, to load the images. The repeat factor 3 displays three images in sequence, on frames 4, 5, and 6.

  4. Change the dwell rate and loop the images.
    Type:  DR 5
    Press:  Alt L
    You should see the loop of the GOES water vapor images on frames 1 through 3.

  5. Toggle to the opposite loop to compare the images. Then stop the loop.
    Press:  Alt O
    Press:  Alt L
  6. Practice comparing the images with the loop control system commands Alt A, Alt B, Alt L, and Alt O that you learned in the Loop Control System lesson.

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