Determination of Mean Square Errors. The mean square error of measure- 
ment at each grid intersection shall be determined from the recorded measure- 
ments. The mean square error in the total model area shall be calculated from the 
differences between the mean value of X, Y, and Z coordinates measured at each 
  
  
  
  
The mean square errors shall be expressed in terms of dimensions correspond- 
ing to the camera format for which the equipment is designed.