International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 2004 
  
  
    
Figure 6. Window Ported NOAA Cessna Citation Undergoing 
Spatial Offset Measurements at Springfield, Ohio 
At the lower altitude of 1316 meters above ground level, no 
pressurization is normally used. Table 3. indicates the 
character of the window’s influences. When no pressurization 
of the cabin is used, the window tends to introduce a moderate 
centering bias and a small increase in RMSE. This is probably 
due to the inability of the mathematical model used for 
calibration to represent the deformations of imagery introduced 
by the window. 
The influences of cabin pressurization for the higher altitude 
flight is indicated in Table 4. Of particular interest in the 
pressurized case is the inability of the calibration model to 
account for image deformations for both the situ and 
laboratory procedures. This is implied by the large bias errors, 
not only elevation, but also for horizontal components when 
compared to the GPS result. 
1.6 
  
  
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1 
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o 
  
METERS 
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a 
  
  
0.2 
   
  
  
  
  
X VENEN 2 
  
RMSE : : ON SITU BLAB : BIAS 
Table3. Single Photo Resection Comparisons for a 
Windowed Port, Un-Pressurized, Multi-Engine Aircraft [Wild 
RC30 15/23 Camera] at 1316 Meters Above Ground for 
Twelve Photographs 
  
  
  
  
  
  
METERS 
  
   
  
   
  
  
Las 0) 
Table 4. . Single Photo 
Resection Comparisons for a Windowed Port, Pressurized, 
Multi-Engine Aircraft [Wild RC30 15/23 Camera] at 5817 
Meters Above Ground for Five Photographs 
DIN SITU MLAB| 
4. CONCLUSION 
The recognition of significant differences between laboratory 
and in situ methods of calibration, and the preparation of 
appropriate software to conduct an in situ calibration has taken 
the USGS closer to achieving a means of calibration that can 
effectively accommodate the added airborne sensors such as 
GPS. 
The Eisenhart concept of “measurement system calibration” 
provides guidelines that can be adapted well to calibration of 
the aerial camera and its supporting equipment and procedures. 
The results of an in situ calibration represent one element in the 
“measurement system specification”. It would remain to 
establish a “state of statistical control” through an ongoing 
process of testing the measurement system by comparison to a 
standard of higher accuracy such as provided by a calibration 
and test range. 
We acknowledge with thanks the support given by the USGS to 
this research and development program. In addition, 
recognition and thanks are given to the Aerial Engineering 
Office of the Ohio DOT for range preparation and film based 
camera flight tests, and to Topo Photo Inc. for conducting flight 
testing of the digital cameras. 
REFERENCES 
Eisenhart, C. (1962) Realistic Evaluation of the Precision and 
Accuracy of Instrument Calibration Systems Journal of 
Research of the National Bureau of Standards — C. Engineering 
and Instrumentation, Vol. 67C, No. 2., April — June 1963 
Saastamoinen, J. (1972) Refraction Photogrammetric 
Engineering, August, 1972, pp. 799-810. 
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