The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
5. CONCLUSIONS 
In this paper we have shown two new methods for the 
correction of atmospheric and BRDF effects in ADS40 images 
which will be implemented in the new ADS40 radiometric 
imaging chain. In contrast to the existing atmospheric 
correction methods in GPro which produce a radiance output, 
the new methods divide out the effect of solar irradiance and 
produce reflectance which is a surface property. A further 
advantage of reflectances is that the image dynamics of the 
different images in an image block is adjusted to match together. 
Both models have the free variables flying and ground height as 
well as view zenith and sun zenith angle. For a fast correction 
the two heights and the sun zenith angle can be set constant. 
The remaining view angle dependence results in a look-up-table 
of correction constants A and B as defined in eqn. (6). The 
ADS40 line scanner geometry allows a simple line by line 
correction. 
The BRDF correction reduces the intrinsic image gradients, 
without removing image fluctuations and is the final step before 
the image mosaicking. Remaining seams can then be removed 
with conventional feathering. This is a step towards an 
automatic generation of huge seamless maps. 
6. OUTLOOK 
In the current implementation the dark pixel value is determined 
for each band separately. Using the geometric sensor model a 
correlation of different bands can improve the selection result 
and lead to a spectral classification. 
For a better support of quantitative methods in remote sensing, 
a step to a more accurate correction will be the integration of 
topographic effects in atmospheric correction. The resulting 
irradiance on the ground depends on slope and aspect of the 
terrain, as well as the sky view factor for each point, i.e. the 
fraction of the sky that is visible from the given point. This 
needs integrating the geometric sensor model and an elevation 
model in the radiometric correction and includes also non-local 
effects, like shadowing from distant points. 
Finally a class specific BRDF modelling would reflect the 
individual differences in BRDF behaviour of ground surfaces. 
This would assist a later classification and time series analysis. 
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