Mirror Cube
Often, users wish to construct a coordinate frame based on the faces of a mirror cube. The Mirror Cube frame assignment method provides a convenient method for repeatedly and accurately locating a coordinate frame with two instruments (typically theodolites). SpatialAnalyzer contains a powerful mirror cube frame assignment tool.
To accomplish a mirror cube frame assignment, point two theodolites at the mirror cube and collimate the instruments with the mirror faces. Record a shot from each theodolite at the cube using the same target name, just as if you were shooting the mirror as a target. If you desire reversed shots, reverse the scope and take another shot, or take multiple shots in each face. In SpatialAnalyzer, select Construct, Frame, and Mirror Cube. You will be prompted to select the target for the mirror. Pick the common target name you used for the measurements. The mirror cube frame assignment dialog will appear. At this point, you may press the Create Frame button to make the coordinate frame, or you may change the options.
Possible Options:
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You may select which instrument represents the X-axis of the coordinate frame.
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You may select or deselect specific shots from each instrument. When there are multiple shots, their vector directions are averaged to calculate the vector displayed below the measurement box.
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The check box for coordinate axes determines whether the axes of the frame are outward along the theodolite vectors or inward toward the theodolites.
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The Axis weighting box allows you to control the distribution of the errors between the two axes.
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Set the Cube face angle (normally 90 degrees). Press Compute after doing this to update!
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The difference between the cube “ideal” angle and the theodolite vector angle will be displayed.
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Use the slider bar to control how far the frame axes are away from the theodolite axes. Sliding the bar to the left places more of the error on the “right-side” instrument.
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Choose carefully when distributing the error. In some cases, it may be better to have no error on one axis since it is difficult to tell if the “error” is coming from the theodolite measurements or the mirror cube itself.