Mirror Cube

Definition

When using a mirror cube to aid in a bundle adjustment one must know the face definitions.

 

Once face 2 is defined the numbering of the rest of the faces moves counterclockwise around the cube, when looking at face 1.

 

Using Mirror Cubes

Though it can be a bit tricky aligning the theodolites to the faces of the mirror cube, the idea is to align a theodolite normal to one face of the mirror cube. Then set up another theodolite normal to a face that is 90° from the face the previous instrument aligned to. In addition to each theodolite measuring the mirror cube and naming those shots the same in the same point group, you will also need to change the point properties from normal shots to mirror cube shots.

To change the point properties, double-click the point in question in the tree. Then click on “Measurement Details”. There should be two measurement details, one from each instrument that measured the mirror cube.

Then single-click the first point in the list and click properties. The window below will then be displayed. In this window you want to click “Advanced Options”, where you will be able to select mirror cube shot and what face of the mirror cube was measured using the aforementioned face definitions. Repeat these steps for the other mirror cube shot.

 

Mirror Cube Frame Construction

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.

At this point, you can now begin to create the mirror cube frame. Go to Theodoilte > Mirror Cube. You will be prompted to select the mirror cube point. After making that selection, the window below will be displayed:

Choosing “Yes” will prompt SA to create a frame based on the current alignment of the two instruments to the mirror cube. Choosing “NO” will allow you to change the properties of the frame which can be done in the window below:

this dialog the user is presented with some possible options.

Once you are satisfied with the frame information, you can select “Create Frame!”. This will construct a frame on the mirror cube measured point utilizing the parameters that were set.