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.