CONCLUSIONS 
For accurate calibration of the internal geometry of a 
television napping system, a reseau grid etched onto the target 
plate is a vital necessity. It permits accurate measurement of 
the geometric distortions in eyery írame of images. However, 
because of the high stability of the magnitude and pattern of 
distortions, measurement of the reseau grid on every frame of 
T 
The goniometer method is capable of providing accurate 
calibration on the internal geometry of the TV optical lens 
system. However, for narrow field-angle system such as the RBV 
camera to be used in the ERTS satellite, the weak geometric 
condition prevents the accurate simultaneous determination of 
both the principal point coordinates (x Y») and the rotational 
parameters 0, ¢ and K. For such systems, the alignment of the | 
optical axis must be known to within few seconds of arc.