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The dynamic performances of an innovative robotic total station (RTS) are assessed while tracking a moving target; also, the results of these performance evaluations are exploited to design its control system. The proposed methodology is novel and uses ad hoc virtual experiments implemented on the digital twin of the studied RTS. This methodology is general and is also applicable for the design of other mechatronic systems. The proposed ad hoc virtual experiments constitute a benchmark for assessing the tracking performances of pointing systems. The application of this methodology to the studied RTS will help complete the RTS's design by determining the most suitable actuators and the control system constants necessary to obtain the assigned dynamic performances. A 3D-printed prototype of the designed RTS was built and is shown in this paper. [ABSTRACT FROM AUTHOR]

The development of multi-sensor systems (MSSs) goes hand in hand with assessing the quality of these complex systems. Therefore, reliable reference information of superior accuracy is essential for validation, serving as ground truth. When the assessment is based on 3D point cloud comparison, appropriate reference environments with suitable geometries are required. However, validation of an MSS can also be performed directly on its 3D position or even its 6D pose. This is particularly suitable for systems without sensors for environmental acquisition. When using kinematic measurement systems, the temporal relationship between the MSS and the reference trajectory must be considered, which can be challenging. Modern sensors of an MSS are often synchronized to GPS time. However, this global time information is not provided for high-accuracy tracking sensors such as robotic total stations (RTSs) or laser trackers (LTs). Instead, only a reference to an internal sensor time is implemented, which does not meet the highest quality requirements for reference trajectories. Depending on the motion speed, time offsets in the millisecond range can lead to significant trajectory inaccuracies. This paper presents investigations for GPS time synchronization of the polar measurement elements of both RTS and LT from Leica Geosystems. While the LT uses a precise trigger signal for the time link, the RTS requires the Measure & Stream application provided by the instrument manufacturer. The two different approaches are presented theoretically. Based on empirical long-term studies, their possibilities and limitations are critically discussed. For the high-frequency LT, reference trajectories with precise synchronization based on GPS time can be reliably realized. With an RTS, improved synchronization can be achieved by using Measure & Stream. Thus, 43 % lower tangential deviations from the reference could be achieved compared to the raw data. However, there are still inconstant time offsets of 63.9 ms on average. Depending on the speed of the target, this can lead to significant position deviations. Further investigations are required. In general, the developed approaches for the realization of GPS-synchronized reference trajectories can be used not only for the quality assessment of MSS, but also for monitoring or kinematic positioning applications. [ABSTRACT FROM AUTHOR]

Robotic Total Stations (RTS) are fully automated theodolites with electronic distance measurement (EDM) that include a number of additional tools (e.g., camera, laser rangefinder, onboard computer, and tracking software, etc.) enabling them to work autonomously. The added tools make RTSs able to track mobile targets on civil structures thus opening to the use of RTSs in structural monitoring. Unfortunately, the available RTSs are able to track a target up to a motion rate of 3 Hz. Reducing mobile masses is a viable design strategy for extending this frequency border. Such a strategy is pursued in this study by proposing the use of parallel pointing systems (PPS) as basic mechanical architectures for RTSs. The literature on PPSs is reviewed and the applicable PPS architectures are selected. Successively, the selected architectures are sized according to RTSs' functional requirements, and the positioning precision of the sized mechanisms is evaluated. The result of this study is that there are three PPS architectures suitable for RTSs, whose detailed comparison is also presented. [ABSTRACT FROM AUTHOR]

Featured Application: As a result of inter-university cooperation, the authors have developed a technological line of 3D printing allowing to build a dedicated protective housing for precise, robotic electronic total stations operating in a displacement monitoring system on a construction site or mining areas. Construction works, especially in the case of large road or tunnel investments, require the active participation of surveyors. It applies to classic geodetic procedures such as staking out or conducting control measurements and continuously monitoring displacements and deformations. Negative factors at surveying sites may hinder the implementation or directly affect the instruments, especially total stations. Heavy dust and rainfall containing harmful and destructive substances can be mentioned here. Contemporary measuring instruments are technologically complex and expensive devices, often exposed to the sun, wind, and frost. To mainly protect robotic total stations, various preventing housings are used. Practice shows, however, that these are half-hearted solutions, often negatively influencing the accuracy of the surveys. Based on the authors' professional and scientific experience, a technological line using the modeling and 3D printing of protective housings for robotic electronic total stations has been developed. The workflow includes dedicated online modeling and printing unique instrument covers that best suit certain sites. The prototype was shielded with an additional hydrophobic layer and tested in a geodetic laboratory. The validation results confirm the high usability of the technological line while maintaining the appropriate millimeter level positioning accuracy and effectiveness of the geodetic monitoring. [ABSTRACT FROM AUTHOR]

Despite the increasing interest in kinematic data acquisition, Robotic Total Stations (RTSs) are still relatively seldom used. No matter if Mobile Mapping Systems or Control & Guidance, GNSS is mostly used as position sensor, which limits the application to outdoor areas. For indoor applications, a combination of relative sensors is usually employed. One reason why RTSs are not used is the challenging time referencing and synchronization. In this work we analyze the challenges of a synchronized kinematic application of RTSs and present solutions. Our approach is based on a wireless network synchronization to establish a precise temporal reference frame. The achievable synchronization quality is thoroughly examined. In addition we develop a kinematic model of spherical measurements, that incorporates timing related parameters. To estimate these parameters we propose a temporal calibration utilizing an industrial robot. Both parts of our approach are evaluated using a test setup of two total stations, proofing an overall synchronization accuracy of 0.2 ms. An overall horizontal kinematic point accuracy of 2.3 mm reveals the potential of sufficiently synchronized RTSs. [ABSTRACT FROM AUTHOR]

Modern robotic total stations (RTS) have the ability to automatically aim, search and track moving targets at high precision thereby enabling kinematic positioning. However, the internal subsystems of the RTS (distance and direction) exhibit time delays which limit the precision positioning of a moving target. These effects are investigated with tracking experiments on a known circular and linear path. A second part of this research investigates small-scale unmanned aerial vehicles (UAV) which use navigation quality GPS as a priori coordinates for photogrammetric processing of acquired images. RTS kinematic positioning was applied to a UAV in a field trial to improve a priori image coordinates and evaluate the method for direct geo-referencing. [ABSTRACT FROM AUTHOR]

Robotic total stations belongs to the most innovative and advanced geodetic instruments used in engineering practice with the performance to maximize productivity and to accomplish requirements concerning to the high angle and distance precision. Robotic Total Station Trimble S8 was used for precise terrestrial measurements of railway track built on ballast-less track construction to diagnose the track behaviour under traffic loading. [ABSTRACT FROM AUTHOR]

In the field of landslide monitoring, the assessment of the spatially-distributed three-dimensional surface displacement is crucial to understand the underlying mechanisms. Nevertheless, available technologies and techniques that provide such a datum are few and often suffer spatio-temporal resolution, logistic and/or financial limitations. In this framework, we developed a methodology that merges the three-dimensional measurements at specific points, acquired by a robotic total station (RTS), and the spatially-distributed data obtained with digital image correlation (DIC) of time-lapse camera photographs, to achieve the spatially-distributed three-dimensional surface displacement. The integration method follows this procedure: i) the DIC results are orthorectified on an existing digital elevation model; ii) the RTS data are rototranslated into the camera coordinate system; iii) the ratio α between displacement vertical component and module measured by the RTS is calculated and interpolated across the region of interest; iv) the orthorectified DIC results are rescaled according to α , obtaining the three surface displacement components; v) the displacement vector is rototranslated into the geographical coordinate system. The sensitivity analysis respect to α revealed that the integration method can be successfully applied even with a limited number of RTS measurement points. The developed methodology has been applied to the Mont de La Saxe rockslide case study, during a phase of strong acceleration. In this period, the displacement magnitudes varied between 0.1 m and 10 m, thus providing a stress-test input for methodology development and validation. The results have been compared with independent ground-based interferometric radar measurements, obtaining 0.99 linear correlation coefficient and median absolute deviation of 0.086 m, which is comparable with the DIC measurement uncertainty. The proposed method is based on the use of low-cost portable and commonly used field equipment, thus it can be easily implemented in existing monitoring networks without additional financial costs. • We developed a data fusion algorithm to merge digital image correlation and robotic total station. • We obtained spatially distributed 3D surface displacement of a landslide. • Our method can be easily applied in operative monitoring without additional financial costs. • We tested our method on the Mont de La Saxe rockslide (Italy), during an emergency period. • We validated our results with GB-InSAR obtaining high agreement. [ABSTRACT FROM AUTHOR]

To validate the accuracy and reliability of onboard sensors for object detection and localization for driver assistance, as well as autonomous driving applications under realistic conditions (indoors and outdoors), a novel tracking system is presented. This tracking system is developed to determine the position and orientation of a slow-moving vehicle during test maneuvers within a reference environment (e.g., car during parking maneuvers), independent of the onboard sensors. One requirement is a 6 degree of freedom (DoF) pose with position uncertainty below 5 mm (3σ), orientation uncertainty below 0.3° (3σ), at a frequency higher than 20 Hz, and with a latency smaller than 500 ms. To compare the results from the reference system with the vehicle's onboard system, synchronization via a Precision Time Protocol (PTP) and system interoperability to a robot operating system (ROS) are achieved. The developed system combines motion capture cameras mounted in a 360° panorama view setup on the vehicle, measuring retroreflective markers distributed over the test site with known coordinates, while robotic total stations measure a prism on the vehicle. A point cloud of the test site serves as a digital twin of the environment, in which the movement of the vehicle is visualized. The results have shown that the fused measurements of these sensors complement each other, so that the accuracy requirements for the 6 DoF pose can be met while allowing a flexible installation in different environments. [ABSTRACT FROM AUTHOR]

The article focuses on three-dimensional (3D) float tracking in quantifying in situ hydrodynamic roughness of submerged floodplain vegetation. A custom-built floating tripod was released on the floodplain and tracked by a robotic total station, while an acoustic Doppler current profiler (ADCP) collected flow velocity profiles and water depth. It was found that median value of the roughness, derived through the equation for one-dimensional free surface flow in a moving window, was independent of the noise in water levels, bottom surface slope and topographic undulations. It is concluded that 3D float tracking is a flexible and detailed method for determining roughness or floodplain vegetation without waves.

• Robotic total stations (RTSs) are applied to subway tunnel displacement monitoring. • An automatic subway tunnel displacement monitoring system is developed. • The mathematical models for both short and long monitoring zone are derived and tested. Real-time displacement monitoring is important for ensuring the safety of subway tunnel structures when construction activities are carried out near them. Owing to the special environmental characteristics of tunnels, many displacement monitoring techniques are either inapplicable to subway tunnel structures or have limitations in terms of the accuracy and automation of monitoring. Therefore, this article focuses on the automatic monitoring of subway tunnel displacement using robotic total stations. Using prisms as reflectors, the robotic total stations can perform highly accurate displacement monitoring by measuring angles and distances in a non-contact manner. A mathematical model for displacement monitoring with one total station in a short monitoring zone is developed, and a model for monitoring a long tunnel zone with multiple total stations is derived to guarantee the accuracy of monitoring. An automatic displacement monitoring system with robotic total stations is built, where the data acquisition and data management of the system are detailed through its hardware composition and software functions, respectively. An experiment on a tunnel showed the available monitoring range of a single robotic total station, and the accuracy of monitoring the long zone with multiple robotic total stations was verified. The application of the monitoring system to the Guangzhou Metro Line 2 confirmed its robustness. [ABSTRACT FROM AUTHOR]