Program EIGEN: If program IMVIS will read an image set label and work with it you can use the same label file and image files to make images of eigen vectors. Simply put an eigen vector image is a rotation of the spectral axis. If you have used program 'make5d' you have seen three of these spectral axes displayed as red, green and blue. Mathe- matically we are not limited to 3 dimensions so all 7 channels of Landsat TM can be rotated as a unit. To understand what is going on take the simple example of a color photograph. Most of the variance of the data is from black to white in the color cube (red, green and blue color space). The line connecting black and white is made up of shades of grey and most colors in a normal photograph are near this line. There are very few really red, green or blue pixels in the average picture or image. Usually the colors we see ar tints of red, green blue or other hues to a grey background. In other words the saturation of most pixels is less than one. Saturation is the absence of white or grey and most colors contain quite a bit of white or grey in them. The result is that the points plotted in the color cube form a cigar shaped cloud that extends from black to white. We cannot improve color perception be scaling the RGB axes because we already go from 0 to 255. What we need to do is to take the points and turn them so that the cigar shaped volume is pointed parallel to the red axis. Now we can take the axis of the 2 remaining dimensions with the most variance and aim this parallel to the green axis and stretch it from 1 to 255. Finally we stretch the remaining blue axis and our points are much further apart in color space. The net result is an image with better visual resolution but not necesarrily one that is of any more value. A number of other games can be played with eigen vectors but a firm grasp of the mathematics is necessary before any sense can be made of the results. Even then it is difficult to understand just what you are looking at. To run program 'eigen' just type: eigen