Exterior orientation completes the processes required to set-up the MPS 
for a specific job employing a given stereo pair. If the stereo pair is 
removed from the Stereoviewer and later required for further digitising, 
the situation can be recovered byt simply repeating the interior 
orientation process and calling up the result of the previous exterior 
orientation. 
4.4 — MPSHO DIGITISING 
The digitizing mode is used to coliect data after a model has been 
oriented. The program allows the operator to specify reject cube 
parameters and sample rate for data sampled in continuous mode. ‘he 
sensitivity and axis system for the hand controls can be changed, and 
the types of data files for storage defined. 
Data can also be sent to an X-Y plotter and/or graphics screen, and be 
overlaid with an annotated map grid. 
The operator has full controi of feature coding of data, and new codes 
can be installed during a digitizing session. 
The function keys on the stereoviewer are used to implement decisions 
during digitizing such as to switch between point and line mode, change 
feature codes etc. 
4.5 MPS60 MPS CALIBRATION PROGRAM 
This program drives to predetermined locations on the celibration grid 
plates, and at each point waits for the operator to accurately position 
the floating ark on the point and record its position. Each point is 
approached four times, with each approach being from a different 
direction. 
The maximum scatter for each group of four pointings can be set, and if 
a group exceeds this value, the set has to be reobserved. 
When observations are complete, the results are displayed, and if 
accepted, they are stored in a correction file for future use, and also 
sent to the stereoviewer. 
After calibration these corrections are automatically appiied. 
4.6 MPS70 CAMERA CALIBRATION PROGRAM 
This program determines the camera calibration constants for lens 
distortion. 
Two photographs of a line pattern are used, one at short focus, and one 
at infinity, with the observations being made monoscopically one photo 
at a time. 
For each photo the operator observes the fiducials, then tracks along 
eaoh iine segment. The program displays the results, and then allows 
the operator to discard any bad readings before computing the final 
parameters. 
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