How to check if your surveyors are holding the pole vertically with the Leica GS18 T

As a survey manager, you may recognise the problem - you ask your teams to ensure the pole is vertical when measuring and staking. When they return from the field, however, there is no way to know if the pole was really held vertically. Until now. When usingLeica Captivatewith aLeica GS18 tGNSS sensor, it is now possible to check if survey teams were holding the pole vertically.

The new “Store tilt only” functionality

Until now we have always explained how the GS18 T is the fastest GNSS RTK rover since the pole no longer needs to be held vertically thanks to tilt-compensated measurements. This is still true and probably the main way of working with the GS18 T. On some projects, though, tilt-compensated measurements are not allowed due to legal requirements. Even on these projects, when the pole must be held vertically, the GS18 T is still the right tool - it can be used to prove the pole was held vertically.

Within Captivate v3.50, a new setting was introduced called “Store tilt only”. When this setting is activated, tilt-compensation is not applied to measurements – the pole must be held vertically. However, when a point is stored, the tilt values are stored together with the point coordinates.

The video below shows how to activate the setting and by tilting the pole, the tilt values are still computed. We then measure some points with the pole held vertically. The measured points, including the tilt values are then imported intoLeica Infinitywhere the tilt values can be seen. The measurements can be analysed – including sorting the points by their tilt values.

How much error can be introduced by not holding the pole vertical?

当用常规方式用GNSS RTK传感器测量点时，必须垂直固定传感器，以使极点在天线的中心垂直下（天线参考点-ARP） - 通过保持图1。从垂直方向上，将引入一个误差，将其引入测量点坐标。倾斜度越大，错误越大。

当以常规方式测量点时，测量师总是通过观察附着在杆上的气泡来尽可能垂直地固定杆子。连接到电线杆的大多数气泡都有20英尺的气泡。这意味着，即使小心翼翼地观看气泡，杆子也很容易被20'倾斜。由20'倾斜的2米极引入了计算的地面坐标为1厘米的误差。

此外,since it is not easy to hold the pole vertical, still and simultaneously measure a point, many users will measure for more than 1 epoch (say 5 epochs). Over this time, any movement in the pole will be averaged.

What tilt value is stored with the point?

If a point is measured with one epoch, then the tilt value that is stored with the point is the tilt value at that epoch. If a point is measured for more than one epoch, then the largest tilt value over the epochs when the point was measured is stored with the point.

Make sure to regularly calibrate the bubble on your pole

Of course, even if the surveyor watches the bubble and carefully holds the pole such that the bubble is centred, this is of no use if the bubble itself is not calibrated. It is a simple task, and we recommend pole bubbles are calibrated once a month, or sooner if the pole is dropped.

In addition, the GS18 T can of course be used to check the calibration of the bubble. Place the pole in a bipod, hold the pole vertically by watching the bubble and observe the tilt values in the Current GS Position panel.

Ask for a demo, if you want to try the new “Store tilt only” functionality

This blog should give you a rough overview of the “Store tilt only” functionality within Leica Captivate and the GS18 T. If you would like more information, please contact your local Leica Geosystems representative – they’ll be more than happy to help.