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9.6 Real-time Data Access - Satellite Imagery

In 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 and manipulate the images. 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 RTIMAGES/GE-VIS.-3

    Image file directory listing for:RTIMAGES/GE-VIS
     Pos Satellite/         Date       Time      Center   Band(s)
         sensor                                 Lat  Lon
     --- -------------  ------------  --------  ---- ---- ------------
     226  G-8 IMG        7 JAN 01007  22:15:00    23   71 1
     225  G-8 IMG        7 JAN 01007  21:15:00    23   71 1
     224  G-8 IMG        7 JAN 01007  20:15:00    23   71 1
     223  G-8 IMG        7 JAN 01007  19:15:00    23   71 1
    IMGLIST: done
    
    (Your listing will differ from the above).

  4. Display the four most recent GOES-East IR images chronologically by using the ALL keyword. Place the images in frames 1 through 4 and center them on Miami.

    Type: IMGDISP RTIMAGES/GE-IR 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-8 IMG       4   07 Jan 01007 19:15:00 RTIMAGES/GE-IR.358
         2[1] G-8 IMG       4   07 Jan 01007 20:15:00 RTIMAGES/GE-IR.359
         3[1] G-8 IMG       4   07 Jan 01007 21:15:00 RTIMAGES/GE-IR.360
         4[1] G-8 IMG       4   07 Jan 01007 22:15:00 RTIMAGES/GE-IR.361
    FRMLIST: Done
    

  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 value is also listed.

         Image Name           Day      Nominal Time   Scan Time    Band
      ----------------      -------    ------------   ---------    ----
      RTIMAGES/GE-IR.358   7 Jan 01007   19:15:00      MISSING       4
    
                            File     Nominal  Image     RAW     TEMP    BRIT
           Lat/Lon      Line/Element  Line/Element               K
     25:46:26 / 80:19:28   633/  661    5317/14429        63     298.5     63
    
    IMGPROBE: Done
    

Manipulating Satellite Images

A major strength of McIDAS as a meteorological data analysis/display package is its ability to display and manipulate satellite images, even if the data is located on a remote server. With the IMGDISP command, you can change the image resolution displayed with the MAG keyword. The IMGREMAP command allows you to remap images into new projections and create new image products.

  1. Display the GINI GOES-West Visible image in its original resolution (1 km) on frame 5. Center the image on Aspen, Colorado (KASE); flip to the frame after the image is loaded; and draw a high resolution map on top of the image.

    Type: ERASE F 1 5
    Type: IMGDISP GINIWEST/GW1KVIS 5 STA=KASE SF=YES REFRESH='EG;MAP H'

    If you receive a partially black image, the image is probably in the process of being received. Try the command again in a few minutes.

  2. Display the GINI GOES-East Visible image in its original resolution (1 km) on frame 1. Center the image on earth coordinates 35° and 75°, and show frame 1 once the image is loaded.

    Type: IMGDISP GINIEAST/GE1KVIS 1 LAT=35 75 SF=YES;MAP

    Again, if you receive a partially black image, the image is probably in the process of being received. Try the command again in a few minutes.

  3. Decrease (blow down) the image resolution of the GINI East VIS image by a factor of 5 and display it on frame 3.

    Type: IMGDISP GINIEAST/GE1KVIS 3 LAT=35 75 SF=YES MAG=-5;MAP

  4. Magnify (blow up) the image resolution of the GINI East VIS image by factor of 5 and display it on frame 2.

    Type: IMGDISP GINIEAST/GE1KVIS 2 LAT=35 75 SF=YES MAG=5;MAP

  5. Change the loop sequence to view the images in the order of increasing resolution.

    Type: LS 3 1 2

  6. Loop the frames.

    Press: Alt L

  7. When finished viewing the loop, turn the looping off.

    Press: Alt L

  8. Change the loop sequence back to loop through the first four frames.

    Type: LB 1 4

  9. Remap the latest GINI GOES East IR image to a mercator projection centered on New York City, and place it in the fourth position in the MYDATA/IMAGES dataset. Change the output resolution, but only create a 480x640 sized image.

    Type: IMGREMAP GINIEAST/GE4KIR MYDATA/IMAGES.4 STATION=KNYC PRO=MERC RES=5 SIZE=480 640

  10. List out the directory information for these images.

    Type: IMGLIST GINIEAST/GE4KIR FORM=BAND;IMGLIST MYDATA/IMAGES.4 FORM=BAND

    Image file directory listing for:GINIEAST/GE4KIR
     Pos Satellite/         Date       Time      Center      Res (km)   Image_Size
         sensor                                 Lat  Lon    Lat   Lon
     --- -------------  ------------  --------  ---- ----  ----- ----- ------------
       1  G-8 IMG        7 JAN 01007  23:01:00    56  113
        Band: 4  10.7 um Surface temp; longwave window       4.0   4.0  1280 x 1280
    IMGLIST: done
    Image file directory listing for:MYDATA/IMAGES
     Pos Satellite/         Date       Time      Center      Res (km)   Image_Size
         sensor                                 Lat  Lon    Lat   Lon
     --- -------------  ------------  --------  ---- ----  ----- ----- ------------
       4  G-8 IMG        7 JAN 01007  23:01:00    41   74
        Band: 4  10.7 um Surface temp; longwave window       1.0   1.0   480 x  640
    IMGLIST: done
    

    Notice that the second image now has a different center lat/lon and is a different size than the original image.

  11. Display the new image in frame 4 and draw a high-resolution map.

    Type: IMGDISP MYDATA/IMAGES.4 4 SF=YES;MAP FILE=OUTLHRES

  12. Loop all of the images.

    Press: Alt L

    By looking at these four images, you should be able to see how simple it is to create different products from the same source image (frame 1) without ever moving the source image from the remote server.

  13. When finished viewing the loop, turn the looping off.

    Press: Alt L

 


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