There is one ambiguity, however, since both GGG and PPH add up 
to PAR. This problem is easily overcome by changing the 
assignment of the pixel values in one of the files from 1, 2 
and 4 to say 1. 4 and 18, The arithmetic combiantions now 
yield the values shown in brackets and no more ambiguity 
exists. 
Theme Classification 
  
It is possible to subject the three files to a classification 
process in the same manner as image files are. The result 
indicates not only the presence or absence of a particular crop 
in a field for the three year period, but also provides this 
information in a year specifio way. For example PPG, PGP and 
GPP can be separated although each has some value in the 
arithmetic operation tvoe overlay. This method provides the 
most sophisticated digital information processing, 
CONCLIISTON 
Standard digital image analysis algorithms can be utilized 
successfullv for further processing and analysing the 
information generated hy the classification of digital image 
data. Therefore, dicital image analvsis systems can be 
utilized as simple land resource information systems. 
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