Full text: Actes du Symposium International de la Commission VII de la Société Internationale de Photogrammétrie et Télédétection (Volume 1)

  
perturbations and residual navigation errors, remain in the printed scene. The 
distortions are adjusted for with the aid of land/water boundaries when the 
analysed data are transferred to the map. 
Temperature values for individual point locations can also be extracted 
from the printout and stored in computer-accessible format. 
  
  
  
    
  
  
| ATMOSPHERIC ENVIRONMENT SERVICE 
| HYDROMETEOROLOGY DIVISION 
Surface Water Temperature 
Area LAK NTARI 
Satellite NV — 7 Orbit 2396 — 
Date 30 SEP/E/ Time _ Q9. GMT 
Mean Temperature — — 12.5 Cc 
| Scale 
  
  
0 50 100 km 
  
  
78° 
  
Fig..‘2 Lake Ontario temperature analysis from data of Fig. 1. 
ATMOSPHERIC CORRECTION 
The water temperatures are retrieved from radiances in the 10.5-11.5 um 
spectral region where attenuation by water vapour and other gases is relatively 
small and reflection from a water surface is also minimal. Hence, water 
temperature can be calculated radiometrically, using Kirchhoff's law and the 
Planck functions, providing that attenuation by the gases, water vapour and 
aerosols is accounted for. 
The atmospheric correction method that is used to correct indicated 
temperature is based on concepts sinilar to those of Wark et al. (1962). The 
method employs the radiative transfer equation to integrate the contributions 
by the different radiating, absorbing and reflecting sources in small wave- 
number increments over the filter band-pass range of the sensor and through a 
layered atmosphere. A method had been developed previously to correct water 
temoeratures measured by an airborne sensor (Shaw and Irbe, 1972), which 
yielded good results (standard error 0.5 C) in temperature surveys on the Great 
Lakes (Irbe, 1972). This method was incorporated with the LOWTRAN (Low 
Resolution Transmission) model of Selby et al. (1976) for use on satellite- 
derived temperatures by Morcrette and Irbe (1978). In a recent study the 
root-mean-square difference between SRT and buoy surface temperature 
measurements on the Great Lakes has been found to be 0.6 C, if the satellite 
zenith angle is less than 45 degrees and the atmosphere is relatively dry and 
clear (Irbe et al., 1981). 
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