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.
- 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.
- Erase graphics frames 1 through 4.
- Type: ERASE G 1 4
- 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).
- 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.
- 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.
- 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
- 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.
- 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.
- 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.
- 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
- 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
- Change the loop sequence to view the images in the order of
increasing resolution.
- Type: LS 3 1 2
- Loop the frames.
- Press: Alt L
- When finished viewing the loop, turn the looping off.
- Press: Alt L
- Change the loop sequence back to loop through the first four frames.
- Type: LB 1 4
- 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
- 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.
- Display the new image in frame 4 and draw a high-resolution map.
- Type: IMGDISP MYDATA/IMAGES.4 4 SF=YES;MAP FILE=OUTLHRES
- 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.
- When finished viewing the loop, turn the looping off.
- Press: Alt L