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IAPRS & SIS, Vol.34, Part 7, "Resource and Environmental Monitoring", Hyderabad, India,2002 
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Figure 1. Design concept of CHHARODI calibration site 
5.1 ARTIFICIAL TARGETS FOR CALIBRATION 
CHHARODI calibration site has been designed as per different 
resolutions of present/future IRS sensors and have been realized 
for single point calibration for multi-spectral LISS-3 type 
sensors of 23.5 mtr. resolution of IRS-1C/1D satellites, four 
point calibration for PANCHROMATIC sensors of IRS-1C/1D 
and LISS-4 multi-spectral type sensors of IRS-P6 of 5.8 mtr. 
resolution and four point calibration for PANCHROMATIC 
type sensors of 1mtr. resolution. The uniform bare soil of 300m 
x 300m size calibration site provides opportunity to carry out 
single point calibration of high resolution sensors. In order to 
characterize the calibration site, large number of reflectance 
measurement of bare soil were carried out using portable 
spectro-radiometer working in 350nm to 1050nm spectral 
range. Reflectance of the site have shown variation within 2- 
3%. In order to calibrate sensor over complete dynamic range, 
multi-point calibration using targets of different reflectance was 
envisaged. It was planned to design artificial targets of suitable 
material and deploy them on the developed calibration site. 
This arrangement could provide all the artificial targets with 
same uniform background after deployment on the site. Since 
the size of the calibration site was limited to 300m x 300m, four 
point calibration target design was finalized as shown in 
Figure-1. 
Three artificial targets of three distinct reflectance and the bare 
soil constituted four calibration targets. The size of each 
artificial target was finalized on the basis of sufficient number 
of pixels available in the image. Due to limited size of the 
calibration site available, it was decided to have artificial 
targets useful for sensors with spatial resolution of 6m or better. 
Looking at the type of high resolution sensors of present and 
future IRS satellites, 50m x 50m size targets were considered 
adequate to meet vicarious calibration requirements of IRS 
satellites. With this size of target, excluding adjacency effect, it 
was possible to have 6x6 pure pixels for PANCHROMATIC 
sensor of IRS-1C/1D. In future, it would be possible to calibrate 
LISS-4 multi-spectral sensor of IRS-P6 using these targets. For 
other higher resolution sensor such as, PANCHROMATIC 
sensor of 1m resolution, it is easily possible to get 30x30 pure 
pixels from 50m x 50m size artificial targets. 
Due to large size of artificial targets, the choice of proper 
target material was a very important consideration during 
design stage. Cloth and tarpaulene based targets were 
   
  
  
  
   
   
   
   
  
   
   
  
  
  
  
  
  
  
  
  
     
  
   
    
    
    
    
     
    
     
   
   
   
   
    
    
    
   
    
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