only need to answer simple 
Some parameters like line 
for conversational processing. Tho user 
questions like yes or no or to type out 
and column numbers. ii " 
The PDCS package was tested by using data from the Bjarka-saby 
area which is situated 200 km south of Linkoping, Sweden. The data 
were collected on three separate occasions. The system was also used 
in other research projects both at the Department of Physical Geog- 
raphy, University of Stockholm and at the Chinese Academy of Fore- 
Stry. 
I got very much help from my Swedish friends when 1 developed 
this system as Chinese guest researen worker in Sweden. The prog- 
ramme should be considered a product of the friendship between 
China and Sweden. Hence the system is named PDCS, meaning Programmes 
Dedicated to China and Sweden. 
THE CHARACTERISTICS 
The whole system indudes the following groups of programmes: 
—Tape handling and subscene extraction 
Statistics and histogramme print 
-Image enhancement 
-Training area extraction, calculation and display 
-Supervised classification 
—-Unsupervised classification 
-Cileaning-up of classified map 
—Accuracy evaluation 
-Result out put 
1. Tape handling and subscene extraction 
The programmes are used when handling original landsat computer 
compatible tapes Produced by BROS data center with different data 
formats. The landsat scene is divided into either four or two 
Strips. The programmes can read and dump any subscenc using only 
one tape station and without temporary memory. They can also read 
the information including ID record. Header record. Ancillary re- 
cord and Annotation record, and print it on the line-printer. 
2. Statistics and histogramme print. 
The progamme gives the user some initial information about the 
subscene under study. 
The statistics calculated by this programme include mean and 
standard deviation of brightness levels of different bands, cova- 
riance and correlation matrices.“ ^... 
The histogramme shows absolute and relative frequency and 
accumulated frequency of brightness levels. 
Both of statictics and histogramme are printed on the line-prin- 
ter. 
3. Image enhancement 
Image enhancement is an important task of image processing. 
EPICS includes the programmes used for a contrast enhan-cement, 
density slicing, combinations of images and edge enhancement. 
One type of contrast enhancement is made by linear transforma- 
tion of the grey scale. Another type of contrast enhancement is 
performed by using equal probability quantizer. In the EPDCS system 
the third method is used. It is mid- way between the first two 
methods I.e. on one hand, it is better than the first one to show 
     
the most : 
better th: 
levels ar 
With - 
scales fo 
Hence, the 
levels, si 
other iy^ 
ficution : 
better th: 
Anoth. 
binations 
At la 
4. Tr 
The c 
sidered t 
tion. The 
the obser 
areas hav 
training 
Gan. perfo 
A. Tp 
30 
re 
Fig 
anticlo