Users with WinTel PC or with Macintosh hardware can use the appropriate copy of the Collage tool supplied on this CD. Follow the directions below.

Users with Macintosh CPU+FPU hardware or with Unix hardware, go to the appropriate Collage site and download the appropriate version of the software. Then follow the directions below.

Collage For Macintosh Web site: http://www.ncsa.uiuc.edu/SDG/Software/MacSoftDesc.html#

Collage For X Windows Web site: http://www.ncsa.uiuc.edu/SDG/Software/UnixSoftDesc.html#

1. Copy/download the Collage file to your computer's hard drive.
2. Set memory allocation for Collage for at least 64 MB on your computer.
3. Open Collage.
4. Select the "Open" option from the File dropdown menu on the menubar.
5. Select (for example) the "MOD04_L2_A2000242.0140.hdf" file; it's on this CD in the "modis" folder that is inside the "data" folder.
6. Click on the [OPEN] button.
7. A "Picker" window opens, with a number of "datasets" (SDSs) on display. Reference numbers are shown, these correspond to the array names listed on the MOD04 Top Level Data Groups page in the MODIS documentation on this CD. (We have included this information for each product on this CD.) Select (for example) the Array: Optical_Depth_Land_And_Ocean, ref = 24.
8. A new window will open, with a large x-y array of numbers. You can scroll up-down and right-left through this data set of aerosol optical depth values.
9. To make an image from the data, select "Generate" from the dropdown menu under "Dataset" on the menubar. A "Size" pop-up window will appear. Since the dataset is not very large (135 x 203) selecting 2 x for display gives a reasonable image size. Click "OK" and the image will appear. Note: clicking on a point in the image will highlight the corresponding value in the window of data values (and vice versa). See the high aerosol optical depth values in the unclouded parts of the image, e.g., at row 75, column 59.