analysis imagery. 



More recently Bendix has been studying the apparent color change 

 of water with water depth using the multispectral equipment. This data 

 collection activity is being conducted in support of a data analysis program 

 being conducted for the Electronics Research Center in Boston. This data 

 was collected at Pentwater which is a small port on the eastern shore of 

 Lake Michigan during the week of 21 July 1969. Lake Michigan was selected 

 as a test site because the water is relatively clear and clean, making the 

 bottom visible out to depths of perhaps 20-30 feet. It was also desired 

 that the test site have a very uniform bottom in order to remove one of the 

 variables from the experiment. The entire eastern shore line of Lake 

 Michigan has an extremely sandy and uniform bottom. The currents flowing 

 north and south along this shore provide an interesting structure for study 

 with multispectral devices. Figure 4 illustrates this structure. The 

 picture is an enlargement of 70-mm imagery from channel 4 of the multi- 

 spectral scanner. The scanner was calibrated in such a way that reflectance 

 values ranging from to 15% would completely fill the dynamic range of the 

 video. The wavelength boundaries of channel 4 extend from about .56 to 

 .62 microns. This range includes the wavelength which has the greatest 

 water penetration in the visible region. The characteristics sandbar 

 structure of the eastern shore of Lake Michigan is clearly visible in this 

 picture . 



27-6 



