International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
Ts = T4 + 1.8 (T4 - T5) + 48(1 - €) - 75 Ae (11) 
Where Ts is the surface temperature, 74 is the brightness 
temperature from band 4 of AVHRR and 75 is the brightness 
temperature from band 5. 
4. MATERIAL AND METHODS 
The ground truth data consisted of 60 color profiles (in Munsell 
notation) of the soil top layer collected in the years of 1995, 
1996 and 1999, from different sites in the Upper Taquari basin. 
Local Area Coverage (LAC) AVHRR/NOAA images were 
acquired from the Satellite Active Archive from the NOAA 
Administration (www.saa.noaa.gov) for the dates the soil 
samples were collected. 
After geometric correction and atmospheric calibration, the 
Vegetation Indices (NDVI, GEMI, MSAVI and PAVI) and 
Emissivity (mean and difference) were calculated. Then, VIs 
and Emissivities were calculated for the ground truth sites 
Different kinds of regression analysis were tested to determine 
the best correlation models among the VIs and Emissivities and 
the soil color. 
Data were separated into two sets, data from 1995 and 1996 
(22 samples), and data from 1999 (37 samples). Regression 
coefficients were calculated using data from 1999 and the 
regression model was tested against 1995 data. 
5. RESULTS 
The calculations made taken all data into consideration shown 
that the best correlations were obtained by linear regression for 
all the vegetation indices and surface emissivity. 
  
2 5 
E r r r r r r 
(H) (H) 0) (V) (C) (O 
  
E 0,45 0,20 0,18 0,03 -0,25 0,06 
  
  
  
  
  
  
  
  
Ag 0,49 0,24 0,15 0,02 -0,29 0,08 
  
Table 2. Values of » and # for Hue, Value and Chroma 
respectively (from left to right) with channel and difference 
emissivity (E) by equation Hue/Value/Chroma = b0 + bl (£) 
When testing the 1995-1996 data against the color (hue, value 
and chroma) grids calculated from the NOAA images, using the 
regression models determined from the 1999 data, the following 
results we obtained: 
  
VI/E r z r r^ r r 
(H) (H) (V) (V, (C) (C) 
  
NDVI 0,86 0,75 0,71 0,51 0,48 0,23 
  
MSAVI | 0,86 0,74 0,73 0,54 0,47 0,22 
  
GEMI | -0,52 0,27 0,60 0,36 0,38 0,14 
  
PAVI 0,86 0,74 0,70 0,49 0,49 0,24 
  
E -0,62 0,39 -0,42 0,18 0,39 0,15 
  
  
Ag -0,71 0,51 -0,43 0,18 0,44 0,19 
  
  
  
  
  
  
  
  
  
The best correlation coefficients were obtained by 
linear/multiple regression: 
VI r rc r^ r 
r r 
(H) (H) (V) (V) (O © 
  
NDVI 0,69 0,47 0,46 0,21 0,36 0,13 
  
MSAVI | 0,69 0,48 0,48 0,23 0,36 0,13 
  
GEMI 0,32 0,10 0,27 0,07 0,31 0,10 
  
  
  
  
  
  
  
PAVI 0,68 0,46 0,46 0,21 0,37 0,14 
  
  
Table 1. Values of correlation coefficient (r) and coefficient of 
determinations (/7) for Hue, Value and Chroma respectively 
(from left to right) with various vegetation indices by equation 
Hue/Value/Chroma = b0 ^ b1 (VI) + b2 (Surface Temperature) 
Table 3. Values of correlation coefficient (r) and coefficient of 
determinations (^) for Hue, Value and Chroma respectively 
(from left to right) with observed and calculated values of Hue, 
Value and Chroma using various vegetation indices, channel 
and difference emissivity. 
5.1 Soil Class Matching 
To evaluate the precision of color calculation trough the 
methodology an application was devised to confirm the soil 
classification of the Upper Taquari Basin, produced earlier by 
EMBRAPA (Brasil, 1997). 
For the application, we selected the Neossolos Quartzarénicos 
Órticos soil class, which covers an area of 13.450 km, 
corresponding to 47% of the Basin area. 
Each pixel of the digital color model calculated, situated inside 
the areas associated to the selected class and in locations where 
the NDVI values ranged from 0 and 0.2, was tested. 
The color interval for the Neossolos Quartzarénicos Orticos soil 
class was determined from a set of morphological descriptions 
of soil profiles collected in the High Paraguai River Basin. 
From the color records provided by EMBRAPA, the color 
component intervals for the selected class are: 2.5YR a 10YR 
for Hue; 3 a 4 for Value; and 2 a 5 for Chroma. 
Four AVHRR images from different years were tested. The 
digital soil color models were calculated using both NDVI and 
MSAVI vegetation indices. 
Considering only the hue component, the comparison gave the 
following results: 
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