Measuring Revolutionised: Reflecting on the First Year of the Leica AP20

Expert Insight

Different scenes of new measurement processes with the tilted Leica AP20 AutoPole.

The Leica AP20 AutoPole has already passed its first year of life on the market and has changed the total station measurement process in surveying and construction environments. Customer testimonials, such as from A.T.G.T.S.M in France, confirm significant productivity gains from the combination of measuring with a tilted pole, automated target searches and target height updates.

But how did users adapt to a new way of measuring with the innovative surveying pole? What challenges and new learnings have emerged from a year of experience with the AP20?

In this expert insight, Leica Geosystems’ Senior Product Engineer, Hannes Maar, discusses these key questions based on collected market feedback and explains new capabilities developed since the release.

How does the Leica AP20 AutoPole impact measuring methods?

The AP20 is a significant step in the goal to automate the whole measurement process for daily surveying and layout tasks.

In the past, great effort has been exerted to improve total station functionalities that ease the user’s burden. Automatic target recognition replaced the need to precisely aim towards prisms. Tracking capabilities allow continuous position updates of a dynamically moving pole for instant point storage and stake out guidance. Imaging and scanning features extended the total station from recording single points into point cloud capture.

Yet major pole-side innovations remained absent, leaving cumbersome manual steps to get from a precise prism measurement down to a reliable pole tip position when the pole could not be held vertically. Whilst the total station height was already automatically measured and recorded, reading and recording pole heights was still a fully manual and error prone process.

The AP20 is the first of its kind which addresses a variety of major challenges occurring directly on the pole. By enabling target identification, automated target height updates and tilt compensated point measurements, the pole component becomes an active part of the total station’s multi-sensor system. Strenuous and delay-causing field practices are no longer needed, such as levelling the pole or entering visually observed pole height readings.

Instead of expending surveying skills to operate a mechanical-optical instrument, the professional’s capacities can be better used to master individual project objectives, from planning site visits to interpretation of data and creation of final deliverables (see The Surveyor 4.0 by Rudolf Staiger).

Consequently, as Rafael Eder shows in his Expert Insight: The AP20-Equipped Surveyor, productivity and flexibility during field work increase and time is saved with every single point measured. At the same time, operators can take their eyes off the analogue bubble and put greater attention on the actual work conditions and surroundings, enhancing safety.

Which users benefit most from the AP20?

For both surveying service providers and building construction professionals trying to optimise their workflow by reducing human error during the stakeout and survey process, the AP20 represents a valuable complement to Leica Geosystems automated total stations.

Survey engineers have observed that immediate target height updates and active tilt compensation allow for quicker and more reliable topographic surveys. The pole’s analogue bubble and the analogue height scale become mostly obsolete, enabling the operator to fully focus on the actual area of interest.

Similarly, the construction surveyor benefits from this flexibility and saves time searching for the correct prism by using the automated target identification and search. Laying out design data requires less iterative ‘stop and go’ steps that stem from having divided attention on the analogue bubble and software guidance and focus is freed to observe on-site hazards.

After over a year on the market, can you describe the transition to the new AP20-enabled automated workflow?

One interesting observation was the paradigm shift from static to dynamic pole handling. Until now the maxim of conventional surveying poles was always, “keep still and upright for accurate measurements.” This was both demanding on operators and a productivity constraint.

With the AP20, you can immediately store tilt compensated measurements once the pole tip has touched the point of interest, significantly speeding up the overall data capture by saving time per single point and allowing more areas to be measured which were previously inaccessible with an upright pole.

Altering a long-trained and practiced survey workflow can be challenging. But once you have switched methods and gained trust based on results, you will see that the minimal effort of integrating the AP20 is more than compensated by an improved workflow, from safety to productivity and accuracy.

Pro tip for tilt compensation: A certain movement of the pole is good and necessary for the tilt compensation mode to remain active and stable for a longer duration. The integrated IMU sensor requires pole accelerations to determine the current attitude in space. Therefore, the more you move in distance and change arbitrary directions, the more stable the calculation.

By starting the tilt compensation mode before you access the area of interest, you enable the AP20 to log IMU data and initialise within seconds while you carry your pole to the point to be measured. Both the Leica AP20 AutoPole White Paper and the how-to video, 3 Easy Steps to Initialise, offer additional tips. I encourage you to try several initialisation methods – from walking arbitrarily from point to point to using a pole waving style – and you will quickly find your individual preference for working with the AP20.

Complemented data quality is another important aspect within the updated workflow. A common geodetic phrase is “One measurement is no measurement.” Every kind of physical measurable is subject to uncertainty and, therefore, statistical statements require more data than a single sensor reading.

In contrast to the conventional surveying pole, the AP20 automatically delivers these quality indicators in real-time. Algorithms which continuously process the streamed total station and IMU observations provide the pole's current orientation in space and its associated uncertainty. As a result, the overall measurement performance of the system “total station and pole” can be determined, and the operator is always aware of the current pole tip position quality. This provides confidence in the field and, thanks to seamless dataflow, extended quality control back in the office.

Have there been improvements after the AP20’s initial release?

Considering customer feedback has been important to us from the beginning and several software and hardware improvements have already been released. Leica Captivate provides new hot keys and favourites to toggle between AP20 functionalities, such as switching tilt compensation from pole tip to reversed direction. An overview of all the upgrades is available in the Leica Captivate v7.51 Release video.

We also extended our accessory portfolio with pole extensions and mini poles that are compatible with the AP20 (see our Accessories catalogue) . This resulted directly from market feedback on the standard AP reflector pole. The newly released GLS52 is a 1-metre-long carbon-made pole extension that can simply be attached to the lower end of the AP reflector pole. This enables the use of tilt compensation with target heights greater than 3 or 4 metres and allows applications such as height and depth determination of manholes or drains.

In contrast to the extensions, we also introduced the GLS53/GLS54 mini poles which fit the AP20 including prism, knob-holder and pole clamp for the controller. The small dimension of around 25 centimetres allows handy usage and highest accuracy of tilt compensation because of the short target height.

With Captivate v8.00, released in June 2023, AP20 tilt compensation is supported inside the Setup application. Setup methods such as Multiple Backsight and Resection can now be performed with tilt compensated measurements as well, a feature you can explore in the Leica Captivate v8.00 Release video.

Additionally, since May 2023, Leica TS13 total stations can connect to the AP20 H and AP20 ID, and can therefore benefit from PoleHeight and TargetID functionalities.

What site challenges remain relevant for surveyors, and what is your advice for navigating these when using the AP20?

We have seen the AP20 eliminates a range of challenges related to site conditions, namely levelling the pole, manual target height updates and manual target searches. However, line of sight constraints can still disrupt the workflow.

For example, the AP20's tilt compensation cannot be fully utilised in working environments with constant line of sight interruptions to the total station. All optical systems, from distance measurement to target search, require a free line of sight between the total station and prism. Without the prism position there is no input for tilt compensation.

While using the AP20 does not fully negate such external interferences , its automated features do give you more options for navigating challenging sites where these are present. You can approach this strategically by early identifying potential obstacles and using the AP20's combination of capabilities to adapt, such as adjusting the pole height, tilting, and even flipping the pole, creating fewer total station setups.

Even with these options, sometimes line of sight interruptions are unavoidable. The good news is, you can recover your target lock quickly once the path to the total station is clear again with automatic target search, ensuring no additional time is lost.

Ready for more details on the technological innovations enabling the AP20’s productivity enhancing capabilities? Download and read the Leica AP20 AutoPole White Paper.

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