orientation to be error free. Rigorous mathematical adjustment 
procedures based upon the Theory of Least Squares are used 
throughout all computations, and the propagation of error by 
covariance analysis techniques indicates the accuracy of the 
reduced data. Assoclated with the reduced position point is 
the error ellipsoid in space caused by the uncertainty of the 
adjustment. The magnitudes of the 3 semi-axes of this error 
ellipsoid are a function of the geometry of the triangulation 
net, and of the random error of the fundamental measurements. 
Thus we have the GDOP (the Geometric Dilution of Precision). 
Geometry is a consideration of the location of each camera 
station with respect to the position point of interest, the 
slant range from each camera to that position point, focal length 
of each camera, direction of the optical axis of each camera, and 
primarily the angle of intersection of the rays in space. The 
random error of the measurement, called the reading error, is 
a function of the quality of the image to be measured, the 
instrument used for the measurement, and the operator making the 
measurement. The compensation for systematic error effects is 
accomplished through the use of a mathematically established 
error theoretical model. Comparison of the estimate of the 
variance resulting from the adjustment with a preestablished 
estimate called the unit variance gives a minimum indication of 
any residual systematic error effects.