White Paper - SX12 Tracking and Target Separation 5
https://geospatial.trimble.com
5
Minimum Prism Separation - Theory
The minimum prism separation required to detect two prisms as separate signals depends on the size of the
prisms and the distance from the total station.
The prism size and the distance from the total station define how big the image of the target appears on the
tracker detector, and how far apart the images of two targets will appear on the detector. The tracker can only
distinguish the two separate target images if they do not overlap.
It's worth noting there is one situation where it is desirable for multiple prisms to be seen as a single target: when
using a 360 prism. The reflected signals from multiple small prisms inside of a 360 prism are seen as one target in
order for the total station to aim to the center of the cluster.
Figure 6. Shows how two prisms will be interpreted as separate targets as long as the image of them on the
tracker detector does not overlap.
Figure 7a. Shows how the angle between the two targets creates a distance between the two images on the
tracker detector.
Figure 7b. Shows the same two targets as in figure 7a but now at a longer distance. The separation between the
two targets are still the same in mm but the longer distance gives a smaller separation angle, and therefore the
two images appear closer together on the tracker detector.
Tracker detector
Image of target 1
Image of target 2
Two images interpreted as separate targets
Tracker detector
Image of target 1
Image of target 2
Two images interpreted as one targets
Angle between targets
Smaller angle between targets
