Full text: Resource and environmental monitoring (A)

For the sume error margin. the number of pixels decreases to 
97.5 *5 (band 69) and 36.3 % (205) for a compression ratio of 
40:1. X 6. 5-75 error margin in band 205 includes 95.8 9o (10-0) 
294, (20:1), and 89.786 (30: 1} of the pixels 
    
d th 
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Band 6% (1011 nm) 
  
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PRAD {%u) 
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2 K. 15 46 189 314 38 3%. 44 dà 43; dd 52 
PRAD (*4) 
Figure 2. Frequency {pixel} distribution of PRAD for band 69 
(1011 nm) and 205 (2319 nmi 
The spectral difference (PRAD) between original and de- 
compressed data for individual pixels behaves similarly to these 
two fidelity assessment cases. An example derived for an 
"alunite" pixel for the compression ratios 10:1, 20:1, and 40:1 
is shown in Figure 3. It indicates that the relative differences for 
the 10:1 and 20:1 compression ratios are very similar with 
errors below 0.3 % in most bands. These errors increase up to 
1% above 2398 nm. As expected, errors of up to 6.3 % occur in 
the strong atmospheric water absorption regions at 1380 nm 
and 1870 nm. The results, retrieved from the comparison of the 
original spectrum and the spectrum compressed at 40:1, 
revealed larger errors, up to 10.2 %, with the strong water 
absorption regions excluded. 
5.2 Data Products 
The results of the endmember selection using the IEA approach 
are summarized in Table 3 for the original and de-compressed 
data cubes. The endmembers found were identified using the 
USGS spectral library and mineral map, which was derived 
from AVIRIS data (USGS, 2002). Compared to the original 
data, the same endmembers were retrieved from data at 
compression ratios 10:1 and 20:1, although the IEA procedure 
selected some of the endmembers in a different order, resulting 
IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India,2002 
PRAD (a) 
  
Ana Sul 13uu 1800 sun 
Wavelength (nm) 
Figure 3. PRAD calonlated from original and de-compressed 
radiance spectra for an “alunite” pixel 
in a different endmember number for a given endmember. 
Accordingly, no endmembers were lost. This is not the case for 
the 40:1 compression ratio where the endmember 14, dickite 
(mixed with kaolinite), was not retrieved. 
Lrg Endmember 
EM # 
CON 
Calcıte (mxed with 
unknown 
Adunite 
A aelimite 
Montmoriionite 
{mixed with 
unknown 
Pca 
Raelimte 
Muscovite {maxed 
with unknown) 
Aaolimnite (mix 
with Alunite) 
Alunite (mixed wit 
Kaclinite) 
unite (mixed with 
EK aochlinite) 
Buddinztonite 
Montmornlionite 
Dickite (mixed with 
Kaolinite? 
m Montenoritionite ER | 
  
ahie 3. Endmembers extracted from the different cubes with 
the automatic [EA procedure 
Differences between endmember spectra, extracted from 
original data and decompressed data, generally increase with 
increasing compression ratio. This trend is reflected by the 
SAM fidelity measure with average values of 0.004 
(compression ration of 10:1), 0.008 (20:1) and 0.010 (40:1) for 
all the endmembers. However, deviations from this trend occur 
for muscovite (endmember 8) and for calcite (2) where the 
SAM values for the 20:1 compression ratio are higher than 
those at the 40:1 ratio. It should be noted in this context that 
endmember spectra, extracted from the original data and de- 
  
   
       
  
     
   
   
   
     
      
   
  
  
   
   
    
   
   
  
     
   
    
   
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