ciduous Conifer Forest which is the sample point of index using GVI data. The vegetation degradation affected 
Figure-1. By using the moving average method, the time area are seen in South America especially in the basin ofthe 
series tendency. of the vegetation activity can be seen Amazon and the La Plata, Middle Africa, and South East 
without. small scattering ofthe NDVI value. Asia. There are some unreasonable spots showing vegetation 
degradaion where the vegetation condition is considered to 
3. METHODOLOGY be rather stable. For the future study, the modification method 
to make standerdize data which include the variety ofthe 
Alter preprocessing ofthe data, the characteristics of 8km sensors, and position should be considered. 
NDVI fluctuation pattern can be obtained and a major pattern 
is selected to represent each class. The represented patterns References 
  
  
  
are used to reclass the existing map fromlow spatial 
? resolution to 8km resolution. The new time series maps for10 — Justice,C.O., Townshend,J.R.D., Holden,B.N., and Tucker,C.J., 
: years data shows the vegetation class during the 10 years 1985, Analysis ofthe phonology ofglobal vegetation using 
and the changes of vegetation map, which had not been meteorological satellite data, INT.J.Remote Sensing, Vol6, 
generated with satellite data, with little ground No.8, ppl1271-1318 
investigation. Tucker, C.J.,1986, Maximumnormalized difference vegetation 
Index images for sub-Sahara Africa for 1983-1985, 
On the other hand, the NDVI fluctuation patterns may change = INT.J.RemoteSensing, Vol7,No.11,pp1383-1384 
depending on the climate conditions in cach year, however, 
the long term tendency ofthe fluctuation is expected to be 
stable in rather long period e.g. 10 years. Figure-3 shows 
samples ofaverage "GVI" fluctuation pattern for "Tropical 
Broadleaf Forest", "Equatorial Rain Forest", "Semi Desert" and 
"Sand Desert and Barren Land" fromApril, 1985 to December, 
1988. From these figures tendencies ofthe fluctuation 
patterns which is declining, increasing or stable can be seen. 
A index which is called vegetation degradation index is 
proposed to indicate the vegetation degradation tendency 
which is defined as the inclination ofthe line-f(x) to fit the 
following formula. 
  
  
0 
T 
   
  
   
y=G (x) 
RS EEE ME 
  
f (x) =ax+b 
EOS 
  
m m= 1'2n 
e Figure-4 Illustration of Definition of 
| Vegetation Degradation Index 
J 4. RESULT AND DISCUSSION 
Outcome(Slide) demonstrates how to define the degradation 
tendency of GVI fluctuation pattern - G(x) - ,and line - f(x)- is 
set to make the area above the line and below the line to be 
Same. Points with smaller inclination ofthe tendency line is 
the area where serious vegetation degradation is proceeding. 
After calculation of the vegetation degradation index foreach 
pixel, a map of vegetation degradation is generated. Outcome( 
Slide)shows the global map ofthe vegetation degradation 
549 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996