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How does robotic positioning work?


Old surveying principles are being used to guide modern machinery




Like GNSS, a robotic total station is a 3D positioning sensor for your 3D grade control system.

Unlike GNSS, however, which is basically a very advanced radio receiver, this sensor is an electro-mechanic and optical positioning device.

This means it can be used under ground, inside buildings or any other place where GNSS won't work because the view of the sky is obstructed.

Additionally, a robotic total station is the most accurate positioning sensor available today for construction 3D grade control applications.

Robotic total station in a 3D machine control system

A robot measures only three parameters: A vertical angle, a horizontal angle and the distance to a target. In our case, the target is mounted on top of a mast that in turn is mounted on the moldboard. The target is mounted on a mast so that an optical line of sight to the robot can be maintained no matter the orientation of the grader.

Both angles are measured by pointing the telescopic axis of the robot towards the target. This turns the two on-board angle sensors, enabling the angles to the target to be read. Now that the robot is pointed toward the target, it sends out infrared light that gets reflected from the target back to the robot. From this reflection, the robot can determine the distance to the target.

Leica PowerTracker used for 3D machine control
The robot also has a built-in tracker. This tracker can utilize more than one operating principle but suffice to say it is an optical system that can 'see' the target and then drive the robot's on-board motors so that the robot is pointed toward the target at all times.

So now we have an instrument that can follow a target on a grader and tell us its location in terms of vertical angle, horizontal angle and slope distance.

We now need to get this information to the 3D grade control system's control box on the grader.

For this purpose, the robot has an on-board radio that sends the positioning information to the grader many times per second.

The grader, in turn,  has a receiving radio that relays this information to the system's control box where it can be processed.
A Leica PowerTracker robotic total station and a target


The robot is set up over a known point in the job site's coordinate system. Because the control box in the grader knows the coordinates of the robot, it can calculate the Northing, Easting and Elevation of the target from the angles and slope distances it receives.

After the angles and distances have been turned into coordinates, the 3D grade control system can commence generating cut/fill information to display to the operator or to drive the hydraulics. You can learn more about how a 3D grade control system does that HERE.

At the time of this writing, Leica, Trimble and Topcon are the only companies offering robotic total stations specifically designed for 3D machine control application.

However, some 3D machine control system from other manufacturers may be able to use one or more of the above-mentioned robots.

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