Rather than make two special photos for these tests, the standard cali- 
bration plate was adopted as the view from one camera, and a special plate 
produced to represent the view from the second camera. A computer program 
was written to generate the necessary data, and it adopts as fixed the x 
and y positions of the grid intersections on the calibration plate. The 
orientation and position of each camera can be selected, as well as the 
height of each grid point. From this data, the X and Y position on the 
ground of each grid point is computed by intersecting the ray from the left 
camera with a horizontal plane at the height of the point. The image posi- 
tion in the right camera is then computed using the collinearity equation 
technique. 
The results include plate co-ordinates for the right camera together 
with ground co-ordinates for each point as well as the camera orientations 
and positions. If required the coordinate system can be rotated to simulate 
oblique photography. 
The grid plates are produced using a pattern generating camera manu- 
factured by the TRC Semiconductor Equipment Corporation. It is normally 
used to produce precise photomasks for integrated circuit manufacture, and 
has a precision of +/- 1/4 micron over the area of the grid. 
As well as providing a test for pointing accuracy and precision of 
the whole system, the grids allow the operator to check other points such 
as: 
The time and diffficulty of setting up base data in the data files. 
How well orienting software copes with large tilts. 
Whether approximate camera co-ordinates are necessary. 
Whether approximate camera orientations are necessary. 
How rapidly does the solution converge. 
How observational errors affect the solution. 
The number and location of fixed points necessary for a good solution. 
Xo RR OR + # 
The grids can provide a system for training operators, and this is 
particularly useful for building confidence in people of limited experience 
in photogrammetry, before they start work on real photographs. 
SUMMARY 
With mechanical analogue stereoplotters it was possible ti directly 
observe any mechanical problems. With an analytical plotter it is essential 
that the user has the same ability to directly evaluate the state of the 
equipment, and the testing procedures described are designed to test the 
detailed performance of both equipment and software, as well as providing 
accuracy tests under simulated operating conditions. 
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