The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Voi. XXXVII. Part B7. Beijing 2008
(Ongi river interruption in south part: from imagery LANDSAT ETM+
data for 23 July, 1999 and 20 September, 2000)
Figure 2. Location of the Ongi river
2.3 Method
Vegetation indices NVI and MSAVI 2 from the SPOT satellite
for vegetation period from April to October 1998-2006 years
used in the study area. Spectral bands Near Infrared 0.78-0.89
pm, Short wave Infrared 1.58-1.75 p m were selected for the
21-30 July, 1998 21-30 July, 1999 21-30 July, 2000
21-30 July, 2004 21-30 July,2005 21-30 July, 2006
0.022675
0.099066
0.175456
0.251847
0.328237
0.404628
0.481018
0.557409
0.633800
Figure 3. Change of vegetation using MSAVI2 index between
years 1998-2006 in the study area
Figure 4. Change of vegetation using NDVI index between
years 1998-2006 in the study area
analysis.
NDVI is normalizad ratio of the NIR and RED bands (1). 3 RESULTS AND DISCUSSION
NDVI =
NIR-RED
NIR + RED
(1)
We made vegetation change analysis on for identifying of land
degradation using remote sensing tools in Ongi river basin in
Mongolia.
Huete (1998) suggested a new vegetation index, which was
designed to minimize the effect of the soil background, which
he called the soil-adjusted vegetation index (SAVI) (2)
developed of an iterated version of this vegetation, which is
called MSAVI2 (3)
SAVI =
NIR - RED
NIR + RED + L
*(1 + L)
(2)
MSAVI 2 =
2NIR +1 - ^{2NIR +1) 2 - S(NIR - RED)
/2
(3)
As a results from the figure 5 and 6 of Onggi River basin’s
vegetation loss has been increasingly 12000 square km. (since
1998 year). Vegetation has a decreasing trend from both
vegetation indexes MSAVI and NDVI (figure 5 and 6). This
analyzes was compared with the results from the “NGO
Ongiinhon” (www.onggiriver.com) research team which used
ground truth data in recent years.
Concluding that this number will be keeping to increase in the
future. Future study should be focused not only on vegetation
condition but should take analysis connected with socio
economic data.
MSAVI varies from 0.022675 to 0.633800 while NDVI values
for vegetation is from 0.01 to 0.89. There is less greenness in
south part area where is interruption river and mining activities
(Figure 3 and 4).