International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004 
0.36 
0.33 
| 0.30 
0.27 
0.24 
0.21 
0.18 
] 9.15 
0.12 
0.09 
0.06 
0.03 
0.00 
raa 
  
180° 
e 
e 
LO 
45.0 
37.5 
30.0 
Figure 6: Modelled NIR reflectance for olive grows where 
NIR - VIS = (NIR — VIS) mean — (NIR — VIS)stddev 
e ed 
x 
S, 
\ 0.36 
0.33 
0.30 
0.27 
0.24 
0.21 
0.18 
0.15 
0.12 
0.09 
0.06 
| 0.03 
* 0.00 
  
52.5 
45.0 
37.5 
30.0 
22.5 
15.0 
7:5 
0.0 
vza 
Figure 7: Modelled NIR reflectance for olive grows where 
NIR - VIS = (NIR — VIS) eus + (NIR —- VIS) die 
  
4 CONCLUSIONS 
It has been shown that the NTAM possesses a big potential to 
reduce BRDF effects in AVHRR imagery of Spain. This is 
quantitatively expressed by the good results in model inversion 
for the two channels and on practically all land cover classes. 
Apart from the good results, the main advantages of the NTAM 
are its physical foundations and its simplicity, as only one set of 
parameters for land cover class and channel has to be provided 
to correct for the whole vegetation period. 
The derived correction parameters offer a great potential for 
interpretation of land cover specific biophysical properties. 
Results of the forward mode of BRDF correction are not 
discussed in this paper. Future work should address the 
transition pixel problem which is enhanced in the forward mode 
of BRDF correction. As landscape in Spain is obviously 
structured on a larger scale than Canada, the land cover based 
approach is to be further investigated. 
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