UAV UWB POSITIONING CLOSE TO BUILDING FACADES: A CASE STUDY

Abstract. Nowadays, Unmanned Aerial Vehicles represent a very popular tool used in dramatically wide range of applications: indeed, their high flexibility, ease of use, and in certain cases quite affordable price make them a very attractive solutions in a number of applications, including surveying and mapping. Despite such a wide range of uses, their usage in automatic/autonomous mode is still restricted by the requirement of the availability of a reliable positioning and navigation system, which in practically all the commercial solutions is represented by the Global Navigation Satellite System (GNSS). Unfortunately, the availability and reliability of GNSS cannot be ensured in all the working conditions of interest. In particular, such condition may not hold downtown, close to high buildings. Since this can also be an operative condition of wide interest, this paper aims at investigating the use of an alternative positioning method that can be integrated with GNSS in order to compensate its unavailability. To be more specific, this paper investigates the positioning performance of an Ultra Wide-Band (UWB) system when an UWB rover is attached to a drone flying close to a building facade, whereas a set of UWB anchors are on the ground, close to the facade. The results obtained in the case study of a building of the University of Padua show that the UWB system positioning performance is quite good (quite less than 1 meter error for most of the time) up to approximately 15–20 meters of distance from the anchors. Close to the top of the building the error significantly increases when using an Extended Kalman filter (EKF) positioning approach, probably mostly due to the low UWB measurement success rate at such heights and to the poor geometric configuration of the UWB network. Nevertheless, a Gauss-Newton-based positioning strategy outperforms the EKF in such critical case, still ensuring errors at 1 meter level

Recent Advancement on the Use of Global Navigation Satellite System-Based Positioning for Intelligent Transport Systems

Non peer reviewe

Positioning Accuracy of Vehicle Trajectories for Road Applications

Global Navigation Satellite Systems (GNSS) has become a kind of positioning standard due to the high penetration rate of this technology on mass market ITS applications. However, this positioning technique remains a real challenge for very demanding services. This paper reports on a practical and methodological approach for the evaluation of the GNSS positioning and attitude of vehicles in real life conditions. Test scenarios have been set up with several positioning sensors mounted on a vehicle for the collection of raw data on different road sections. The measurement of a high quality reference trajectory allowed to estimate position accuracy under different environmental conditions. We will show in detail the results and identify some typical situations where the quality of GNSS-only positioning is reduced and may impact the level of ITS services, e.g. road user charging or safety applications

Collaborative navigation as a solution for PNT applications in GNSS challenged environments: report on field trials of a joint FIG / IAG working group

PNT stands for Positioning, Navigation, and Timing. Space-based PNT refers to the capabilities enabled by GNSS, and enhanced by Ground and Space-based Augmentation Systems (GBAS and SBAS), which provide position, velocity, and timing information to an unlimited number of users around the world, allowing every user to operate in the same reference system and timing standard. Such information has become increasingly critical to the security, safety, prosperity, and overall qualityof-life of many citizens. As a result, space-based PNT is now widely recognized as an essential element of the global information infrastructure. This paper discusses the importance of the availability and continuity of PNT information, whose application, scope and significance have exploded in the past 10–15 years. A paradigm shift in the navigation solution has been observed in recent years. It has been manifested by an evolution from traditional single sensor-based solutions, to multiple sensor-based solutions and ultimately to collaborative navigation and layered sensing, using non-traditional sensors and techniques – so called signals of opportunity. A joint working group under the auspices of the International Federation of Surveyors (FIG) and the International Association of Geodesy (IAG), entitled ‘Ubiquitous Positioning Systems’ investigated the use of Collaborative Positioning (CP) through several field trials over the past four years. In this paper, the concept of CP is discussed in detail and selected results of these experiments are presented. It is demonstrated here, that CP is a viable solution if a ‘network’ or ‘neighbourhood’ of users is to be positioned / navigated together, as it increases the accuracy, integrity, availability, and continuity of the PNT information for all users

Position Accuracy with Redundant MEMS IMU for Road Applications

The diversity of road applications and intelligent transportation systems (ITS) makes the definition of positioning integrity a real challenge because the requirements are changing from one application to another. Even within liability or safety critical applications, the role of positioning may vary if the application layer requires a position at specific location (e.g. emergency call) or a series of positions along a vehicle’s trajectory (e.g. transport of dangerous goods). -- This paper is focusing on the positioning assessment of vehicle trajectories collected by different navigation sensors (GNSS and redundant MEMS Inertial Measurement Units (R-IMU)) in real test scenarios. Single GNSS, integrated GNSS and R-IMU are compared to a high quality ground truth solution based on a high-end navigation system. The low cost equipment is based on a single frequency GNSS receiver combined with four IMUs (triad of accelerometers and gyroscopes) of the same type. The architecture and the algorithms for the sensors integration have been developed at EPFL and are used on several mobile platforms (land vehicles, ultra-light planes, micro-drones). A series of measurements of different kind and thus dynamics have been conducted by EPFL and NTUA during a scientific mission form the COST Action TU1302 on Satellite Positioning Performance Assessment for Road Transport (SaPPART). Several test scenarios were performed in different traffic and environmental conditions in order to face with challenging GNSS signal reception. Road sections have been selected ranging from open sky condition (e.g. rural roads) down to poor GNSS reception (e.g. urban road network). The evaluation of the positioning quality is done by comparing the position-output from several solutions: single GNSS, D-GNSS, integrated GNSS/R-IMU. The comparison to a reference trajectory of precisely time-stamped positions allows to calculate and to plot along-track as well as cross-track differences. This visualisation of the results make sense for many road applications like road user charging (RUC), pay as you drive and some advanced driver assistance systems (ADAS). Finally, this quality assessment of vehicle positioning in real conditions will be a valuable material for future simulations of navigation systems in severe conditions. This contribution is fully adequate to the goals of the COST Action SaPPART, especially for the definition of the performance assessment methodology

Experimental Evaluation of a UWB-Based Cooperative Positioning System for Pedestrians in GNSS-Denied Environment

Cooperative positioning (CP) utilises information sharing among multiple nodes to enable positioning in Global Navigation Satellite System (GNSS)-denied environments. This paper reports the performance of a CP system for pedestrians using Ultra-Wide Band (UWB) technology in GNSS-denied environments. This data set was collected as part of a benchmarking measurement campaign carried out at the Ohio State University in October 2017. Pedestrians were equipped with a variety of sensors, including two different UWB systems, on a specially designed helmet serving as a mobile multi-sensor platform for CP. Different users were walking in stop-and-go mode along trajectories with predefined checkpoints and under various challenging environments. In the developed CP network, both Peer-to-Infrastructure (P2I) and Peer-to-Peer (P2P) measurements are used for positioning of the pedestrians. It is realised that the proposed system can achieve decimetre-level accuracies (on average, around 20 cm) in the complete absence of GNSS signals, provided that the measurements from infrastructure nodes are available and the network geometry is good. In the absence of these good conditions, the results show that the average accuracy degrades to meter level. Further, it is experimentally demonstrated that inclusion of P2P cooperative range observations further enhances the positioning accuracy and, in extreme cases when only one infrastructure measurement is available, P2P CP may reduce positioning errors by up to 95%. The complete test setup, the methodology for development, and data collection are discussed in this paper. In the next version of this system, additional observations such as the Wi-Fi, camera, and other signals of opportunity will be included

A Benchmarking Measurement Campaign to Support Ubiquitous Localization in GNSS Denied and Indoor Environments

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Experimental assessment of the accuracy of a Ground-Based Radar Interferometer in a fully controlled laboratory environment

[EN] Ground Based Radar Interferometry (GBRI) counts almost twenty years of maturity. Ever since its infancy, GBRI has been extensively used in structural health monitoring, thanks to its high sampling rate (up to 200 Hz) and remote, ultra-high displacement observation accuracy (claimed to be of the order of ± 0.01 mm in lab. conditions) at multi-point locations on a structure. Nevertheless, despite the fact that GBRI has already been extensively used for bridge monitoring projects, the published results of the comparisons derived between GBRI and other technologies (e.g., accelerometers, seismometers and Laser Doppler Vibrometers) are usually limited to real structures cases at operational conditions; and therefore, an exhaustive assessment of the inherent quality measures of GBRI observables is still missing. This paper presents the results obtained from an exhaustive investigation of the performance capabilities of a GBRI sensor (IBIS-S sensor, IDS Radar®), in terms of precision (repeatability) and accuracy (trueness) at fully controlled, lab conditions. Dynamic displacements of a sinusoidal form were produced using an automatically operated portable shake table and on-purpose built software. Testing scenarios cover a frequency range corresponding to structural modal frequencies (up to 20 Hz) and an amplitude range of 10-5 to 10-2 m. The measurements of a Laser Tracker sensor serve as a benchmark against which the results of the GBRI unit are assessed, in terms of displacement accuracy and frequency estimation correctness.Piniotis, G.; Gikas, V. (2023). Experimental assessment of the accuracy of a Ground-Based Radar Interferometer in a fully controlled laboratory environment. Editorial Universitat Politècnica de València. 665-671. http://hdl.handle.net/10251/19234266567

Performance evaluation of a novel terrain aiding algorithm for GNSS tracking in forested environments

25th International Technical Meeting of the Satellite Division of the Institute of Navigation 2012, ION GNSS 2012 Volume 3, 2012, Pages 2083-2090This research investigates the ability of Digital Surface Models (DSM) to aid GNSS tracking in forested environments. Particularly, a new augmentation methodology named "Terrain-Aiding" (TA) is proposed, evaluated and testified. Although "Terrain-Aiding" is a term already used in airborne military navigation, in this paper it is defined with an entirely different meaning; it forms an extension to the well-known technique of Height-Aiding (HA). In order to validate the proposed algorithm and associated software a set of dedicated experiments were carried out in a forested area located nearby Athens, Greece. To accommodate data collection, a specifically designed on-purpose build backpack platform was designed to carry two receivers of different (mapping- and geodetic-) grade characteristics. High accuracy DSM tiles were used to represent the terrain surface. Consequently, the TA algorithm was assessed in terms of GNSS positional availability, accuracy and external reliability in absolute terms (i.e. against a well-defined benchmark trajectory). The results obtained indicate an improvement in GNSS availability of the order of 37%, when only three satellites are available, whereas GNSS accuracy is significantly improved in cases of marginal conditions. Furthermore, the external reliability was considerably improved by more than 80%

Combined Coastal Sea Level Estimation Considering Astronomical Tide and Storm Surge Effects: Model Development and Its Application in Thermaikos Gulf, Greece

Tide gauge recordings furnish the longest and almost the most continuous data source of sea level monitoring. Traditionally, they are collected using tide gauge instrumentation fixed at seaport locations to provide a time series of sea level estimates relative to a local geodetic benchmark. Sea level tidal observables are distinguished in the astronomical tide component originating from the attraction of the Earth–Moon–Sun gravitational system, and the storm surges ought to have meteorological effects due to wind and atmospheric air pressure variation. This study provides a comprehensive methodological approach and software to compute sea level considering astronomical tides enhanced by storm surge effects. The model is realized and assessed using a long-standing set of 21 consecutive years of tidal and meteorological measurements originating from Thermaikos Gulf, Greece. Analyses show model verification and conclusions about the tidal behavior of the test area, suggesting a satisfactory agreement (86% Willmott Skill factor, 9 cm standard deviation) between predicted and observed sea level estimates, accounting for amplitude and the time shift of skew surges