Collimation is the process consists of making rays from two instruments accurately parallel to each other. Using SA, this is done by having two theodolites measure the face of the other. Collimation can be useful when needing to align multiple theodolites to each other without having a common reference system. This application is more suitable for evaluating angles, due to the fact that he distance is unknown until its input manually by the user. Preparation for the collimation of theodolites is not as involved as bundle adjust, but can be just as useful.
So after having each theodolite measure the others face, en- sure that those points were named the same so that there are two measurement details for that observation.
Now open the measurement details and double-click one of the point observations.
In the “Spherical Measurement” dialog box select Advanced Options.
There select Collimation Shot and pick and instrument. (Choose the instrument that was measured in that observation NOT the instrument that did the measuring)
Click OK and then repeat for the second observation.
Now that the collimation points have been established you are now ready to collimate the instruments. To do this select Theodolite > Collimation. The dialog box shown below will be displayed.
To collimate the instruments to each other, a distance is needed. There are a few options, but in its most basic form you know the ap- proximate distance between the instruments and it can be input here manually:
Selecting OK will prompt SA to align the instruments based on the collimation shots and the distance between the two instruments.
A line for each line of sight will be created which should be 180° from each other. If there are more than two instruments you can repeat these steps making. (Follow Inst0 to Inst1, then Inst1 to Inst2, then Inst2 to inst3, so on and so forth for additional instruments).
The collimation Type select offers two options for greater control:
Full Collimation. This option will perfectly align the collimation shots.
No-Tilt Collimation. Collimation can be performed while holding gravity. This option will align the shots as well as is possible while holding the instrument Rx and Ry orientations.
There are 3 baseline methods available for collimation:
Enter Distance (d). Provides a means to enter a know distance between the instruments. The selected instruments are aligned using the collimation shots and this entered value.
Distance Determined From Scale-Bar (length=d). This method assumes that the distance (d) is the length of a measured scale bar. Collimation is computed based upon a common collimation shot and two measured points that define the scale- bar location and distance based on the given length.
Distance Determined From Known Point. The 3rd method still used the collimation point for alignment but establishes distance and orientation based upon a know point in space with respect to the non-moving instrument. The measurement of this known point from the moving instrument along with the collimation shot is used for alignment.
The Instrument Collimation dialog also offers an option to Zero the Moving Instrument Azimuth. This option requires a live instrument connection, and when selected, will zero the instrument’s Azimuth value based upon the collimation shot-line.