How Do I Use The Sigma0 Program?

Mac Users, Please Note: The instructions below were meant for the PC compatible version of Sigma0. However, Sigma0 users for the Mac can also follow the description below. Sigma0 works very similarly on both the PC and Mac.

The basic requirements to run the Sigma0 program are an IBM-PC or compatible computer that will support an eight bit color monitor and that has at least 4 megabytes of RAM. The following instructions assume the user has a basic knowledge of computer operations, such as copying, scrolling, and opening programs. These instructions are meant only to get you started on the programs. The best way to go through them is with a computer and the CD readily in hand. Complete instructions are included in the documentation files in the Software directory.

Sigma0 for the PC

Please note: At the time of this writing, the beta version of Sigma0 was included in the CD and, while functional, it does contain software bugs. JPL provides this software "AS IS" and makes no guarantees as to its fitness for any particular purpose.

Installing Sigma0 on the PC

Displaying an Image

Choose the TESTDATA.STK image file from the /SOFTWARE/SIGMA0/TESTDATA directory. You will now be presented with a histogram and another blank window. Click OK. The histogram will disappear and an image will be displayed.

Place the cursor on a dark portion and look at the top of the image. You will see numbers representing the X and Y coordinates as well as a number representing the radar backscatter value or . These numbers tell you your location in the image and how reflective the surface was to the radar. A large negative indicates very low reflectivity and appears as quite dark whereas a number close to zero indicates very high reflectivity and will be quite light. The values are used by scientists who analyze radar images.

Close the file via File | Close and then open it again via File | Open Cmprsd Stokes. Again select HH and the histogram will appear. This time, however, move the tip of the cursor to the gray bar underneath the histogram:

Click and hold down the cursor while moving it to the left, until it is located about one half to two thirds of the way from the left of the bar. Click OK. Notice how much more contrast is evident in this image.

Now let's draw out a box around one of those areas. Move the cursor to a location left and above the area you want to study. Click and hold the mouse and move it downward and to the right. You should see a green box. Go to Image | Zoom In. Notice that this acts like a magnifying glass. Zoom in several times. You will continue to enlarge the area of interest. Draw out the window (box on bottom right) so that you can still see a lot of the image. After you have zoomed several times, you will notice that the command Image | Display Sigma 0s becomes darkened. Drag down and select it. You will now see all the printed in the boxes.

Zoom out now using Image | Normal Size or Image | Zoom Out. You will find that Zoom Out is especially useful for large images - it is the equivalent of Scale to Fit Window in NIH Image.

Draw a small box again in a dark area. Go to Statistics | Mean and std dev. This produces a window which gives the mean value of . in the selected box as well as the standard deviation. You will note that this can be saved as text and printed.

We believe these instructions should get you up and running.

GOOD LUCK AND HAVE FUN!