A major strength of McIDAS as a meteorological data analysis/display package is its ability to display and manipulate satellite images. In this lesson, you will use the IMGREMAP and IMGOPER commands to remap images and create new image products.

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=KDCA 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            4.0   4.0  1337 x 1604
   
   Image file directory listing for:TI
    Pos Satellite/         Date       Time      Center      Res (km)   Image_Size
        sensor                                 Lat  Lon    Lat   Lon
    --- -------------  ------------  --------  ---- ----  ----- ----- ------------
      4  GOES-7        13 MAR 93072  18:01:00    41   78
       Band: 1   0.65 um Daytime cloud detection            4.0   4.0  2274 x 1940
   

   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=KDCA REFRESH='MAP LALO -3 GRA=(GRA) IMA=(GRA)'

   Type: IMGDISP TI.4 2 STATION=KDCA 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