GNSS setting out, with no need to level the pole vertically?

Setting out with a GNSS antenna is a tricky task. Looking at the instructions and values on the controller screen, moving the pole to the required position, and ensuring the pole is vertical by centering the pole bubble - all at the same time - needs careful execution and is not easy, especially when time pressure is high. With the new Leica GS18 T, setting out is much more convenient and faster than ever before. In this article Paul Dainty explains more.

Surveyors and setting out engineers are no different. Pressure at work is high. There are the usual time-critical tasks to do on a typical construction site such as checking the as-built structure, or setting out earthworks or building foundations.

The pressure is on. A crew and an expensive machine are waiting.

Sometimes though, the pressure on site can get really high. Imagine, the excavator machine has just arrived on site earlier than planned and it is ready to start the earthworks. The problem is the profile boards have not been set out, and this needs to be done before the earthworks can start. The setting out engineer is the only person who can do this. The pressure is on. He must set out these profile boards right now, as fast as possible, to the highest possible accuracy of course while a very expensive machine is waiting idle, not to even mention dozens of impatient workers.

Setting out with a conventional GNSS RTK rover can be slow

With a conventional GNSS RTK rover, setting out is a rather slow and methodical procedure. This is because the pole needs to be held vertically at the same time as looking at the setting out information on the controller screen all the while moving the pole into position. The GNSS position is calculated to the antenna, which is fixed onto a 1.8 m or 2 m pole. Hence, for the setting out information on the screen to be correct, the pole must be held vertically by centering the pole bubble.

To set out a position accurately, it is needed to perform several tasks at the same time:

• Look at the setting out instructions and values on the controller screen
• Walk and orientate: Move the pole to the required position so that the stake values are close to zero
• Ensure the pole is vertical by centering the pole bubble

Simplified setting out with the new Leica GS18 T. Looking at the pole bubble and holding the pole vertical (like in the image) are history.

As it is extremely difficult to do these all at the same time, it is generally preferred to follow those tasks in an iterative process:

It needs to be an iterative process because by centering the bubble to ensure the pole is vertical in step 3, we probably need to move the antenna, and need to go to step 1 again to check the setting out instructions on the screen. Then do step 2 again to adjust the pole position, and so on. To set out a position accurately enough, the process probably has to be performed two or three times, which is not particularly difficult, but it does take time to do it properly.

Now returning to our site, imagine the excavator and the crew of workers waiting for you to carefully set out the profile boards, performing the iterative setting out process on each one. The situation is likely to be very stressful and mistakes are likely to happen, slowing the process down further.

Imagine being able to set out without needing to perform this iterative process.

Well, now that is possible, using the Leica GS18 T with tilt compensation. The GS18 T is the first GNSS RTK rover to allow staking out with a tilted pole. Because the GS18 T combines seamlessly with the Leica Captivate field software, tilt compensated measurements are possible in any app within the software. We can measure and stake points, lines, roads or whatever is needed, all with a tilted pole.

The new Leica GS18 T – different from all other GNSS sensors

So how does the tilt compensation work and how does it remove the need for the iterative setting out process? For the GS18 T, Leica Geosystems developed a very special IMU and a patented method of combining the IMU and GNSS data. With this new technology, it is not necessary anymore to rely on a magnetometer to calculate the tilt direction for each measurement. The GS18 T with tilt compensation is calibration free and the sensor is immune to magnetic disturbances. With its remarkable ability to use it not only for measuring but also for staking out, the GS18 T is different from all other tilt compensating GNSS sensors currently in the market.

Setting out is made much easier because the tilt compensation removes the need to center the bubble to make the pole vertical. This means that when setting out with the GS18 T, the engineer only needs to do the following two steps:

• Look at the setting out instructions and values on the controller screen
• Move the pole tip to the required position so that the stake values are close to zero

Intuitive stake out: With the GS18 T the position of the pole and the distance of the pole tip to the stake point are graphically shown in real time on the controller with a powerful 3D viewer.

The following video sequence gives a good impression how it works:

As the setting out engineer does not need to ensure the pole is vertical by centering the pole bubble any more, the process is not iterative anymore. Setting out is much more comfortable and can be done faster than ever before.

With the new Leica GS18 T setting out can be done quickly, confidently and accurately with the minimum of fuss and reduced stress. Simply get the job done on time.

Ask for a demo, if you want to try out the new GS18 T on your own.

Readers who want to get their own impression of the world’s fastest GNSS RTK rover, contact your local Leica Geosystems distributor and ask for a demo. Demos are possible from November 2017 onward. The Leica Geosystems distribution network will be at your service.

Paul Dainty
Application engineer at Leica Geosystems