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The step size is given by the smallest pattern size required to follow the 
terrain accurately while obtaining enough information for a reliable X para 
llax signal. This pattern size is not dependent so much upon the terrain slope 
as upon the detail size on the plates. Because any model will contain the type 
of detail which will contract the pattern to its smallest size, the line width 
has to be set for this smallest pattern size. This dictates a step of 1.5 mm for 
the orthophoto print. Figure 5 is a section of an orthophotograph produced by 
the instrument. 
Y Profiling Mode: 
The Y profiling mode operation is identical to the X profiling mode with the 
X and Y drives interchanged. 
Contouring Mode: 
In the contouring mode the space rod carriage is driven in the X and Y 
direction to null the X parallax signal while the Z carriage is held at a given 
elevation. The nulling operation is always performed perpendicular to the con 
tour; the trace velocity along the contour is given by the correlation signal. 
The pen used to plot the contour line on the paper is automatically lifted 
when the correlation signal falls below a given level or the X parallax signal 
exceeds a given level to avoid marking a contour when the information obtained 
from the plates is not reliable. The contouring mode is a semi-automatic pro 
cedure where the operator has to choose the contour and the Stereomat will trace 
that contour automatically. 
The Stereomat can be made to plot a series of contours when the operator 
lays reflective tape perpendicular to the contour lines to be traced. The machine 
will then step in the Z direction every time it reaches this tape, but at the 
highest or lowest level the operator has to set the Stereomat to a new contour. 
Automatic Orientation Mode: 
In this mode of operation, which can be used for the relative orientation, the 
operator inserts two plates, zeros the Y parallax in the two Kappa stations and 
actuages the automatic orientation mode. The space rod carriage moves auto 
matically through a programmed sequence of orientation stations continuously 
removing the Y parallax while approaching each station and not moving to the 
next station before the position is reached and the Y parallax is zero. The speed 
of this procedure is controlled by the correlation signal while movement of the 
Z carriage is used to null the X parallax. The usual time required to perform 
automatic relative orientation is from 3 l/Z to 4 1/2 minutes.