International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
  
  
  
  
  
  
  
  
    
  
  
  
  
  
  
  
  
  
  
  
  
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d. Asphalt road 
Figure 3. Contrast of reflectance spectrum curve 
As the fourth band of SPOT-5 is beyond the band scope of wild 
radiometer, in order to ensure the integrity and aesthetics of the 
comparison chart, during the resampling process of measured 
spectral reflectance curves, the reflectance of the part (the 
fourth band) beyond the band scope shall be given man-made 
based on past experience and trends of the curve, thus 
comparative analysis mainly focuses on comparing the 
differences of the first three bands. We can conclude from the 
figure that the measured reflectance curve of the first three 
bands is more similar to the curve after the Model FLAASH 
atmospheric correction. 
Soil reflectance is related to soil types, water content and 
surface roughness and other factors, and there are no obvious 
peaks and valleys of reflectance of soil surface under the 
natural state. The farmlands in the study region have just been 
harvested with straws covering the soil surface, so there is a 
valley at the 0.65 um of the three curves, similar to vegetation. 
However, it is not so different from the near-infrared 
reflectance. As shown in Figure 3(b), the vegetation spectral 
begin to decrease from the green band (0.55 um), a small valley 
at the red band (0.65 um), which is due to the strong absorption 
10 
effect of chlorophyll to red light and strong reflect action of 
chlorophyll to green light; then there is a peak of reflection at 
the rear-infrared (0.84 um), which is subject to the effect of the 
structure of vegetation leaf cells, the unique characteristic of 
vegetation. Under the case that the reflectance of both models 
are slightly smaller than the measured reflectance, accuracy of 
FLAASH is higher than that of QUAC. The water body in the 
study area includes sediment, chlorophyll and other substances, 
and the is relatively shallow, also influenced by the bottom 
materials and the spectral transmittance of the water, so at the 
visible-near infrared, reflectance rises with the increase of 
wavelength instead of reducing. Reflectance curve of asphalt 
road surrounding the farmland rises slowly at the visible-near 
infrared band, and then becomes gentle after that. From Figure 
3(d)we can see that the value of the measured reflectance curve 
is larger, and the reflectance after FLAASH atmospheric 
correction is more similar to the characteristics of the measured 
spectral. 
3.3.3 RVI comparative analysis: The vegetation index (VI) is 
the index mainly reflecting the differences of vegetation among 
visible light, near infrared reflectance and soil background. In 
the field of remote sensing application, the index of various 
vegetations in certain conditions can be used for illustrating the 
growth situation of vegetation quantitatively. In order to 
evaluate the influences of the types of atmospheric corrective 
models on calculation of vegetation index, here the RVI is 
taken as the example; the three types of RVI value including 
the original DN value, the value of FLAASH and QUAC after 
atmospheric correction have been compared with each other. 
  
  
  
  
  
  
vegetation 
Figure 4. Contrast of the value of RVI 
water asphalt soil 
As shown in figure 4, for various ground features, the value of 
RVI after atmospheric correction is a little bit higher (excluding 
waters) than the calculation of original value of DN. Therein, 
the value of RVI after atmospheric correction increases 
obviously in the filed of vegetation, and the value of RVI after 
atmospheric correction based on the model of FLAASH nearly 
reaches 2.5. Thus it can be seen that the atmospheric correction 
could conspicuously increase the differences of RVI between 
the vegetation-covered area and non-vegetation covered area, 
which makes the vegetation information gets more prominent. 
4. CONCLUSIONS 
This paper makes a summary and comparison between Model 
FLAASH atmospheric correction and Model QUAC 
atmospheric correction, and on this basis the contrastive 
analysis of visual effect, reflectance spectral curve effect and 
RVI effect. The results of the trail show that: the images after 
the two model atmospheric corrections appear to be brighter 
visually and contrast is enhanced; while the reflection spectral 
characteristics of the surface features are largely restored and 
emphasis the vegetation information, indicating that the two 
models can be applied to the SPOT-5 images in southern hilly