McIDAS Learning Guide
Version 2008

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Satellite Imagery - Manipulating Images

1. Remap the latest GOES-7 Visible image in the BLIZZARD dataset to a mercator projection centered on Washington DC, and place it in the fourth position in the TI dataset. Keep the output resolution at 4 km, and remap the entire area

   Type:  IMGREMAP GV4 TI.4 STATION=DCA PRO=MERC RES=4 SIZE=ALL

2. List out the directory information for these images.

   Type:  IMGLIST GV4 FORM=BAND;IMGLIST TI.4 FORM=BAND

   Image file directory listing for:GV4 Pos Satellite/ Date Time Center Res (km) Image_Size sensor Lat Lon Lat Lon --- ------------- ------------ -------- ---- ---- ----- ----- ------------ 3 GOES-7 13 MAR 93072 18:01:00 26 87 Band: 1 0.65 um Daytime cloud detection 4.32 3.61 1337 x 1604 Image file directory listing for:TI Pos Satellite/ Date Time Center Res (km) Image_Size sensor Lat Lon Lat Lon --- ------------- ------------ -------- ---- ---- ----- ----- ------------ 1 GOES-7 13 MAR 93072 18:01:00 42 78 Band: 1 0.65 um Daytime cloud detection 2.99 2.99 2347 x 2392

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

3. Show frame 1. Display the images in frames 1 and 2 centered over Washington DC. Draw a map of dashed lat/lon lines in color 3 on each image. You will learn more about the MAP command in the Graphics and the Cursor lesson.

   Type:  SF 1

   Type:  IMGDISP GV4 1 STATION=DCA REFRESH='MAP LALO -3 GRA=(GRA) IMA=(GRA)'

   Type:  IMGDISP TI.4 2 STATION=DCA REFRESH='MAP LALO -3 GRA=(GRA) IMA=(GRA)'

4. Set the loop sequence, and loop between the frames.

   Type:  LS 1-2

   Press:  Alt L

   Notice that the images have different projections.


5. Stop the loop.

   Press:  Alt L

6. Create a new image using subsequent GOES-7 IR images in the BLIZZARD dataset using the formula GI4.1 - GI4.2. This will show the shift in the clouds from one image to the next. Put the new image into position 5 of the TI dataset.

   Type:  IMGOPER GI4.1 GI4.2 TI.5 COEF=1 -1 FORM=ADD MAG=-3

   IMGOPER generates a new image by applying mathematical functions to data from one or more source images. The following equation computes the data value for each line/element pair in the destination image. This operation is performed repeatedly using data from source image line/element pairs as input values (input) until the entire image is completed.

   output data value=
   FUNC[ACON+(MCON*(FORM((COEF1*(OFF1+((SIGN1)*input1)**POW1))
   	(COEF2*(OFF2+((SIGN2)*input2)**POW2)) . .
   	(COEFn*(OFFn+((SIGNn)*inputn)**POWn)))))]

   
   

   The part of the equation operating on a single input data value, (COEFn*(OFFn+((SIGNn)*inputn)**POWn)) , is referred to as a term. n represents the number of sdataset images. It may not be larger than 100. input1 . . n represents the individual data values from each of the source images. The FORM keyword determines how the terms are combined. For example, if you specify FORM=MULT, the terms are multiplied.

7. Erase the maps in graphics frames 4 through 6, and display the images that you just used in frames 3-5.

   Type:  ERASE G 4 6

   Type:  IMGDISP GI4.1 3 MAG=-3

   Type:  IMGDISP GI4.2 4 MAG=-3

   Type:  IMGDISP TI.5 5

8. Loop through the images.

   Type:  LS 3-5

   Press:  Alt L

9. Stop the loop.

   Press:  Alt L

10. Add a label to the image frame.

    Type:  SF 5;FRMLABEL IMA=5 "CLOUD MOVEMENT FROM 17:01 TO 17:31

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