ABSTRACT.  

The presentation discuses the urgent need for very high precision positioning and timing with high integrity to support emerging safety of life applications.  The briefing will review current developments undertaken by RTCA, EUROCAE and ICAO and identify gaps in performance that may be required for aviation and non-aviation related safety-of-life applications. 

Speaker Biography

Tim Murphy is a Boeing Senior Technical Fellow in Boeing Commercial Airplane group where he is a member of the Airplane Systems organization. Tim has 30+ years of experience in the field of radio navigation and communications systems for civil aviation. The current focus of his work is avionics for new airplane product development, and next generation CNS technologies to support Air Traffic Management.  Tim is the executive focal for regulatory issues associated with Aircraft Tracking and Flight Data Recording.  Tim's primary expertise is in navigation systems including satellite navigation systems (GPS, GPS augmentations, GPS modernization, GPS Landing Systems) as well as conventional navigation systems (VOR, DME, ILS etc.). Tim also has extensive experience and expertise in communications systems including satellite and ground based communications systems. 

Tim is very active in the development of domestic international standards for use of satellite navigation, communications and surveillance by commercial aviation. He is the panel member nominated by the International Coordinating Council of Aerospace Industries Association (ICCAIA) to the International Civil Aviation Organization (ICAO) Navigation Systems Panel.  He is the chairmana member of the CNS/ATM subcommittee of ICCAIA which coordinates all industry work with ICAO, a branch of the United Nations which deals with Standards and Recommended Practices to support safety and regularity civil aviation operations.  He currently serves as a member of the National Space-Based Position Navigation and Timing (PNT) Advisory Board providing advice to the US government on policy issues associated with GPS and other navigation capabilities.  He has been an active participant within RTCA, serving on three different government advisory committees in the areas of Satellite Navigation, Satellite Communications and Automatic Flight Guidance and Control Systems. He is a fellow of the Institute of Navigation, has published more than 44 papers and holds 17 patents with more pending. He received a BSEE and MSEE from Ohio University where he was a Stocker fellow and graduate research intern at the Ohio University Avionics Engineering Center.
 

ABSTRACT.  

With the increasing ubiquity of smartphones, users are now routinely carrying a variety of sensors with them wherever they go. These devices are enabling technologies for ubiquitous computing, facilitating continuous updates of a user’s context. They have built-in GNSS, Wi-Fi, Bluetooth, cameras, MEMS-based inertial sensors, etc. Sensor fusion techniques are required to enable robust positioning and navigation in complex environments needed by consumer users, vehicles, and pedestrians. The talk aims to highlight current developments of localization technologies and techniques using smartphones.

Speaker Biography

Dr. Guenther Retscher holds an undergraduate degree in Surveying, a PhD and a Habilitation (venia docendi) in Applied Geodesy from TU Wien with the focus on Mobile Multi-sensor Systems for Personal Navigation and Location-based Services. Guenther’s research interests include positioning and navigation with GNSS, location-based services, indoor and pedestrian navigation, applications of multi-sensor systems, smartphone positioning and sensor fusion. Guenther is currently the coordinator of IAG Special Study Group SG 4.1.1 on Positioning Using Smartphones and the co-chair of the joint IAG Working Group WG 4.1.1 and FIG WG 5.5 on Multi-Sensor Systems.

ABSTRACT.  

At present, GNSS usage and testing in autonomous vehicle navigation ranges from low-cost, single-frequency GPS with short-baseline real-time kinematic (RTK) augmentation for drone applications to network RTK and Precise Point Position (PPP) augmentation of mass-market, dual-frequency, multi-constellation GNSS chips for next-generation automotive applications.

This talk will summarize the current use of GNSS technology in autonomous systems, its limits, and assess the need for GNSS.  Key challenges for high-accuracy GNSS usage are considered.  The case for and against high-accuracy GNSS as a sensor amongst sensors in mass-market applications will be made.  And, finally, other industries that should benefit from these developments will be discussed.
 

Speaker Biography

Sunil Bisnath is a Full Professor in the Department of Earth and Space Science and Engineering at York University in Toronto, Canada. His research centres on precise GNSS-focussed positioning and navigation. He holds an Honours B.Sc. and M.Sc. in Surveying Science from the University of Toronto and a Ph.D. in Geodesy and Geomatics Engineering from the University of New Brunswick.

ABSTRACT.  

An 18 month trial of high accuracy satellite positioning technology known as a Satellite Based Augmentation System, or SBAS, for the Australasian region was funded with $12 million from the Australian Government and a further $2 million for direct demonstrator project funding from the New Zealand Government. On behalf of the Australian and New Zealand governments, Geoscience Australia partnered with Land Information New Zealand (LINZ) to undertake the trial, and FrontierSI was engaged to manage 27 demonstrator projects across ten industry sectors. The trial has assessed the economic, social and environmental benefits of improved positioning technologies and has demonstrated tangible benefits across a range of industry sectors. Accurate and reliable positioning information has significant economic benefits with an expected value of $6.2 billion for Australia, $1.4 billion for New Zealand and a total of $7.6 billion for both countries over 30 years. The SBAS Test-bed project successfully demonstrated the benefits for Australia to implement an operational SBAS and a national positioning capability. General benefits of an operational SBAS include wider coverage, enhanced accuracy down to the decimetre level, signal integrity and reduced commercial costs and infrastructure investment.

Speaker Biography

Anna Riddell is a geodesist working in the Positioning Australia program at Geoscience Australia. After graduating from the University of Tasmania with a Bachelor of Surveying and Spatial Science (Honours), Anna worked at Geoscience Australia in the National Positioning program on GNSS analysis, GNSS antenna calibration and also installation of the AuScope GNSS network stations. For the last couple of years Anna has been back at the University of Tasmania completing her PhD on understanding the vertical movement of the Australian tectonic plate, and also determining how the Earth’s centre of mass influences precise positioning.  

ABSTRACT.  

From the days of tall ships and sextants, the principles of safe navigation stem from being able to determine a ship’s position, relative to hazards to navigation. Today, GNSS has become the primary source of position, navigation and timing (PNT) information and has enhanced the safe navigation of ships around the world. As industry continually strives to extract efficiencies in shipping, the reliance on resilient and highly accurate PNT information is vital.

More recently, the accuracy and integrity of GNSS standard positioning services has meant that AMSA can discontinue its terrestrial radiobeacon Differential Global Positioning Service (DGPS) on 1 July 2020. Some other countries have already done so. Whilst standard positioning services offer positional accuracy well within IMO’s requirements for marine navigation, SBAS and other augmentation services can deliver improved accuracies and thereby significant efficiencies for the maritime sector.

Whilst the IMO considers that formal recognition of satellite-based augmentation services for marine navigation is not necessary, international organisations such as IALA, and IEC are working to develop guidance on transitioning from DGPS to SBAS (IALA) and test standards to facilitate the standardisation of SBAS-enabled shipborne receivers (IEC).

The Australian Maritime Safety Authority (AMSA) remains an advocate for resilient PNT in the maritime industry. AMSA will work domestically to ensure maritime interests are part of the SBAS program.. AMSA continues to contribute to work internationally in support of the development of SBAS standards.

Grant Judson is Principal Advisor, Navigation at the Australian Maritime Safety Authority.

ABSTRACT.  

Within the SBAS test-bed campaign, the performance of the SBAS different solution methods (L1, DFMC SBAS and SBAS-based PPP) was assessed in two main areas: road transport and mining. For road transport, tests were conducted under various environments, including open sky, low-density Urban, and high-density urban environments. It is shown that SBAS performance is strongly dependent on the application environment. Performance analysis demonstrated that L1 SBAS solutions provide better positioning than single point positioning, and the DFMC SBAS solutions have better precision than L1 SBAS solutions. Furthermore, SBAS-based PPP solutions delivered a few-dm accuracy, which is a bit worse than traditional PPP with corrections received via the Internet. Both L1 and DFMC SBAS are useful for many road transport applications, but only SBAS-based PPP is useful for applications that need sub-m accuracy. In the mining applications, and after convergence of the PPP solution, the multi-constellation SBAS-based PPP solutions can be used in digital pegging and autonomous operations of trucks and drill machines. Independent from the test-bed campaign, the DFMC SBAS data was assessed for Localizer Performance with Vertical guidance down to 200 ft (LPV200) in aviation. The new ED-259 standards were used,and testing were carried out over a simulated grid covering the entire Asia-Pacific region. Results show that the differential correction (DFC) residual errors have the dominant contribution in the values of the protection levels needed in integrity monitoring, whereas other error sources such as the airborne receiver errors, the tropospheric and the ionosphere residual errors have smaller impacts. At a known station, the position errors were found to be at the sub-meter level and were always bounded by the protection levels (PLs), which were always less the alert limit of LPV-200. This indicates the capacity of achieving the required LPV-200 integrity monitoring in the main areas of the Asia-pacific region.

ABSTRACT.  

The SBAS test-bed project showcased the application of accurate positioning across ten industry sectors in Australia and New Zealand. Position Partners participated in the Construction and Rail demonstrator projects which were carried out on real-world operating conditions in construction sites and rail lines.

The construction project validated the performance of the new SBAS L1, SBAS DFMC and PPP signals in civil and building construction sites. Applications that require accurate and low-cost positioning include collision avoidance, personnel tracking and structural inspections with RPAS. The new SBAS signals were shown to deliver increased accuracies for low-cost devices in emerging safety applications.

The rail project tested the performance of the new SBAS and PPP solutions along Tasmania’s rural and suburban rail lines. The testing environment included virtual canyons formed by steep terrain and vegetation canopy that degraded satellite availability. The results showed that, even in some challenging conditions, SBAS positions are within sub-metre accuracies.

Automation and safety systems for professional industries typically require increasing levels of accuracy and assurance, yet customers are demanding lower cost positioning devices, which will ultimately increase adoption. The use of SBAS and PPP signals will contribute to a high accuracy low cost service model and is expected to be received positively by the construction and rail industries.

ABSTRACT. This presentation summarises the work carried out by FrontierSI as part of the Australia and New Zealand Satellite-Based Augmentation System (SBAS) project from January 2017 to the present day. SBAS is a technology designed to augment Global Navigational Satellite Systems (GNSS) positioning by broadcasting correction data from a geostationary satellite to users within a fixed service region. Three different correction services were broadcast and tested, one of which has not yet undergone widespread evaluation elsewhere in the world. SBAS was originally designed as an aviation technology to help improve vertical guidance, however since its inception it has been used in many non-aviation fields. SBAS improves standalone GNSS positioning in a number of key areas including accuracy, availability and integrity.

FrontierSI was tasked with managing 27 projects testing SBAS technology across 10 industry sectors in Australia and New Zealand including aviation, road, rail, maritime, agriculture, construction, consumer, resources, utilities, and spatial. Performance baselines from the demonstrator projects formed an input for an economic benefits study, which forecast the expected financial impact of the SBAS on each industry sector as well as the economies of both countries. This study highlighted further applications of the SBAS which may be realised in the coming years, as well as areas that will require further research and development. This presentation highlights the results of FrontierSI's testing campaigns, the indicative performance of the SBAS in relevant industry use-cases, and the potential benefits unlocked as a result of the new signals.

ABSTRACT. This paper describes the design of an SBAS E5b channel for Precise Point Positioning (PPP) service. The primary objective is to define the signal structure, modulation and encoding strategy as well as message content and format. The signal definition is designed to be as interoperable as possible to ease interoperability with other PPP services and facilitate service penetration at the user level. This work is conducted in collaboration with Thales Australia and Thales Alenia Space.

ABSTRACT. In 2017, a two-year test-bed for a second generation Satellite-Based Augmentation System (SBAS) was initiated in Australia and New Zealand in preparation for building an operational system. In addition to the traditional SBAS L1 service for GPS, the test-bed provided the dual-frequency multi-constellation (DFMC) SBAS service, and the precise point positioning (PPP) service using GPS and Galileo. In this study, and for the first time, the positioning performance of the different SBAS services is presented in the mining sector. It is shown that after convergence of the horizontal PPP solutions, the RMSE is at sub-dm to dm. Furthermore, this contribution presents and compares two weighting models that can benefit the new DFMC SBAS in environments with large multipath, firstly not considering the signal smoothing time and secondly considering it. The results show that considering the smoothing time in the weighting model is helpful to improve the positioning accuracy without degrading the availability.

ABSTRACT. The effect of trans-ionospheric satellite signal propagation diminishes the positional accuracy of GNSS observations to a high extend in the equatorial region. Differential GPS (DGPS) technique is applied to overcome ionospheric issues by providing locally generated corrections. The increasing use of Satellite Based Augmentation Systems (SBAS) provides DGPS correction data via geostationary satellites with accessible bandwidths by all GNSS receivers without requirement of additional hardware. The Indian SBAS GPS Aided Geo Augmented Navigation (GAGAN) and the Trimble RTXIO (Real Time eXtended – Central Asia) are available over Sri Lankan region. The first is a free service covering the entire Indian region by three geostationary satellites and the second is a globally available paid service with a restricted access even for Trimble GNSS users. Continuous observations of four days were carried out to analyses the performance of these correction services under varying ionospheric conditions. For the experiment, one GNSS receiver was configured with GAGAN and the other with RTX CenterPoint augmentations, while a third receiver was set to perform standalone GNSS observation. Both GAGAN and CenterPoint RTX shows similar positioning accuracies varying between zero to 130 cm and observed to be changing with the variation of the Total Electron Content (TEC) depending on time of the day. Standard deviation (SD) values were investigated for four different time periods covering certain times during day and night. The TEC declining phase during late afternoon from 4:30 to 20:30 Local Time (LT) resulted in highest SD, depicting a degraded system performance than during the high TEC period from 10:30 am to 16.30 LT. However, SD were minimum during quiet TEC phase at night from 20:30 to 5:30 LT. CenterPoint RTX was marginally outperforming compared to GAGAN services during both the disturbed and quiet ionospheric conditions.

ABSTRACT. In contrast to outdoor localization that relies primarily on GNSS (Global Navigation Satellite Systems) signals, localization in indoor environments is quite challenging due to the absence of GNSS signals and presence of various objects that reflect and disperse the signals such as Wi-Fi (Wireless Fidelity), Ultra-Wide Band (UWB) or other SOP (Signals of Opportunity) used for localization. Cooperative Localization (CL) has proven to be one of the practical approaches for localization in GNSS denied and challenging environments. This paper analyses the experimental performance of an indoor cooperative pedestrian localization approach that relies on UWB based relative range measurements among the pedestrians, as well as relative measurements between the pedestrians and static infrastructure nodes. The experimental setup uses a network containing about 30 static infrastructure nodes and four pedestrians moving in a hallway. Each infrastructure node and pedestrian are equipped with a UWB sensor for relative range measurements. Additionally, some of the pedestrians also carry a low-cost inertial sensor, but inertial observations are not used in this paper. A centralized extended Kalman filter (EKF) is used to localize all the pedestrians using the relative range information and knowledge about the infrastructure nodes. It is observed that the network geometry perceived by a pedestrian has a significant impact on its localization accuracy. The results demonstrate that the proposed approach can achieve decimetre level localization accuracies, provided a good network geometry, and enough range observations are available. Towards either end of the hallway, significant degradation in the localization accuracy is observed due to the combined effect of the decrease in the number of available range observations and poor network geometry. The accuracy achieved in the proposed setup may be further improved by the inclusion of inertial sensor observations and precise time synchronization among the nodes.

ABSTRACT. Wi-Fi-based positioning technology has grown rapidly over the past 20 years along with the fast development and applications of smartphones for indoor positioning. On the other hand, Wi-Fi is increasingly accepted for outdoor positioning due to the availability and popularity of public Wi-Fi in worldwide cities. Because GPS signals are often interrupted and unstable in the downtown areas with high-rise surrounded, Wi-Fi becomes an ideal positioning technology as a substitution of GPS. Especially after the release of the IEEE 802.11mc standard last year, researchers and specialists from industries were attracted immediately after the release. The new standard provides a fine time measurement (FTM) protocol for us to use multiple round-trip time (RTT) rather than the received signal strength indicator (RSSI) for calculating the distance between a Wi-Fi access point (AP) and a mobile end-user device. This paper presents an evaluation and comparison study between Wi-Fi RTT and GPS based localisations in an outdoor space located in a downtown area in Melbourne city. Based on the same testing environment and same testing points within a central city area, both GPS and Wi-Fi RTT are tested and analyzed. All the coordinates received from GPS were converted to the Australian grid coordinate system and then to the local coordinate system for the ease of comparison. Results showed that the average positioning accuracies from the two technologies are 2.6m and 1.2m respectively. The Wi-Fi RTT technology demonstrated a much better performance both in accuracy and stability.

ABSTRACT. Locata is a terrestrially-based system that provides timing and ranging signals from which a user can position, navigate, or time (PNT) synchronise. It therefore can provide enhanced PNT services in otherwise GNSS-degraded or GNSS-denied environments – such as indoors, in urban canyons, warehouses, open-pit mines, ports, cities, or hostile military environments – by deploying a “local PNT network” which is designed-for-purpose, and wholly under the control of the user. Locata technology (LocataTech) is an Australian-based, privately developed, commercial-off-the-shelf PNT system. It provides accurate PNT solutions that not only have great potential to support critical national infrastructure, but is also a proven capability designed to meet many present and future PNT requirements. LocataTech has been independently proven to deliver: • High-precision Survey-Grade Carrier-Phase Solution: ~ cm-level resolution, • Lower-precision Consumer-Level Code Solution: ~ metre-level resolution, • Network Synchronisation: ≤ one nanosecond precision, • Frequency Stability: ≤ 1x10-15 (one part per quadrillion - better than Stratum 1 specification), and • Unprecedented Multipath Mitigation: the new Locata VRay antenna allows systems to be installed which deliver cm-level indoors and in difficult industrial automation environments, where multipath is by far the largest error source for radionavigation systems.

Despite a decade of steadily increasing interest in LocataTech’s PNT capabilities, in 2015 Locata largely “disappeared” from public view. The reason for this was that Locata had signed “Non-Disclosure Agreements (NDA’s)” with multiple large global companies. Those partners were developing new fully-autonomous vehicles for critical infrastructure installations around the world, and they were basing their new machines on Locata’s capabilities in GNSS-challenged environments.

In the past few months details of a number of these installations have become public, and hence Locata can now discuss these developments without breaking NDA obligations. This presentation will present information on the newly-emerging autonomous machines LocataTech has enabled for container terminals, logistics terminals, indoor autonomous vehicles and more. It will also detail the new multipath mitigation technologies based on the company’s unique VRay antenna, and show how this new antenna has allowed ultra-reliable cm-level performance for the machines in areas where GNSS-type positioning has not been possible before. Finally, the presentation will introduce next-generation LocataTech miniaturisation developments which will soon bring this technology to many new applications, including warehousing, UAVs, autonomous cars, malls and eventually mobile phones.

ABSTRACT. Many critical modern systems such as mobile phone networks, banking, data networks, and electricity grids demand high-accuracy time and frequency stability across specified areas, as set out in IEEE specification standard 1588. Military digital communications systems also rely heavily on accurate time. To date, the preferred method to achieve adequate performance in most applications is via synchronisation from GPS or other space-based positioning systems. However, the vulnerability of GPS signals is a growing concern (especially for military functions), and hence precision alternatives are being sought by many entities. This presentation details the latest demonstrated time transfer and synchronisation capabilities of the U.S. Air Force's Non-GPS-Based Positioning System (NGBPS) at the White Sands Missile Range (WSMR). The NGBPS uses Locata’s radio-based Positioning, Navigation and Time (PNT) technology as the core synchronisation capability when GPS is being actively jammed across large areas of the WSMR. The U.S. Naval Observatory (USNO) had independently proven in previous tests in Washington DC that Locata’s TimeLoc™ technology could deliver exceptional synchronisation, time transfer and frequency stability in city/urban environments. In this new demonstration Locata’s TimeLoc synchronisation was tested by the USAF over significantly larger areas than ever before. By using the NGBPS network now installed across thousands of square kilometres at WSMR, USNO timing experts demonstrated Locata-enabled synchronisation at the sub-nanosecond level, even when transmitters were separated by over 74km. In addition, the engineers showed nanosecond-accurate UTC-based time transfer across the breadth of the NGBPS network, as well as comparable timing performance in a receiver in a land-based vehicle which was moving all over the WSMR. The Locata system demonstrated these capabilities without using atomic clocks or any form of external aiding to accurately synchronise its signal transmitters. This paper presents details of test parameters and equipment configurations used to establish Locata’s absolute and relative time synchronisation performance. The presentation also discusses how Locata’s area of transmission can be readily increased to cover substantially larger areas if required for safety-of-life, military or Government-mandated systems.

ABSTRACT. The availability of Global Navigation Satellite Systems (GNSS) greatly facilitate precise orbit determination of many Low Earth Orbit (LEO) satellites. However, satellites or spacecraft in orbits bound to Small Celestial Bodies (SCB) like asteroids do not have an established external architecture to support a similar navigation process. Ground based radiometric methods commonly employed for orbit determination of satellites in Earth orbit are also not ideal for these orbits owing to the necessity to perform target relative navigation in SCBs. In regard to the technology requirements for space exploration or space resource utilization, there is considerable emphasis on the necessity to develop autonomy and distributed mission architecture to support large scale missions of the future. In this research, we investigate the utility of a maximum likelihood maximization approach such as Simultaneous Localization and Mapping (SLAM) as a method for autonomous spacecraft navigation in SCBs. SLAM, being an actively researched topic in terrestrial robotics, has established framework for autonomous navigation that could be adapted to comply with the navigation requirements in the proximity of SCBs. Noting that the interest of the current state of the art techniques for navigation in SCBs is predominantly on the accuracy of navigation, the focus of this investigation is on how autonomy could be incorporated in the navigation process without having to sacrifice considerable accuracy.

ABSTRACT. In this paper we propose a concise algorithm for solving the self-localization problem in a least squares sense, based on direction of arrival measurements of a number of celestial bodies. The main advantage of this algorithm is that it transforms the search for the optimal fix, into a generalized eigen-decomposition where only the largest eigenvalue is of interest. Several high-level languages and programming platforms such as Matlab, already provide routines that selectively and efficiently solve for the largest or smallest eigenvalue. The second part of the paper considers refining this solution by deriving the MLE (maximum likelihood estimation) estimator, and using the obtained fix as an initial solution to compute an MLE optimal fix in an ECEF (Earth-Centered-Earth-Fixed) frame. Several computer simulations are given to compare the bias and accuracy of both estimators.

ABSTRACT. Geodesy is undergoing a golden era. Newer and ever more advanced missions such as Champ, Grace, Grace-FO, GOCE, DinSAR, IceSat2 are using incredibly high precision measuring techniques to sense ever finer dynamic processes in the Earth system. However much of this instrumentation is considered classical (or Newtonian) and in order to improve on these traditional geodetic techniques, the science of quantum mechanics is being applied to geodesy. Quantum phenomena such as entanglement, superposition and the Heisenberg uncertainty principle are being applied to try to improve sensing techniques applied to gravimeters, radar and synthetic aperture radar and satellite-to satellite tracking. This presentation will attempt to introduce some of these new concepts and report on advances in the various fields that will contribute to a even finer understanding of dynamic Earth processes.

ABSTRACT. Cold atom inertial sensors are beginning to make their way out of the lab and into the field. These devices exhibit biases and sensitivities that improve upon those of existing state-of-the-art sensors by several orders of magnitude. The extent to which these improvements enable long-term, unaided inertial navigation is an open question, and one that we hope to address in part by the error analysis, modelling and simulation of cold atom inertial sensors in various scenarios and configurations. To-date, among other aspects, we have considered the feasibility of standalone cold atom inertial navigation units; the impacts of gravity map quality; environmental noise effects; and the relative contributions of error sources in long-term inertial navigation. I will discuss elements of these and others that form part of our joint ANU-RMIT research program.

ABSTRACT. While quantum accelerometers advance with extremely low drift/bias, their sensing capabilities are limited by two problems when compared to classical accelerometers, i.e., low sample rate constrained on cold atom interrogation time and small dynamic range known as signal phase wrapping. The research teams at RMIT University and at the Australia National University have a joint research project on evaluating the advance of quantum sensing in conventional inertial navigation implementation using statistical signal processing techniques. One of the developments is the work on the fusion of classical and quantum accelerometers for improving inertial navigation performance. The development is based on the quantum accelerometer prototype and signal model developed by the team at the Australia National University.

In this work, we propose a probabilistic data fusion method that enables quantum accelerometers to be utilized in the practical inertial navigation applications with an enhanced performance. Both classical and quantum sensors are in the same navigation platform. The readings of the classical sensor are used to unwrap the real phase of quantum accelerometer signal via a maximum likelihood estimator. We show that the actual phase of the quantum accelerometer can be identified by fusing it with the output of a classical accelerometer on the platform and thus the acceleration reading from the quantum accelerometer is recovered. The recovered acceleration measurement of quantum accelerometer is then used to re-calibrate the classical accelerometer. Discussions on fusion error and potential solutions are presented. We demonstrate the enhanced error performance achieved by the proposed fusion method using a simulated 1D inertial navigation scenario.

ABSTRACT. Collecting data for testing and validation of Cooperative Positioning (CP) systems is time-consuming and often requires a big bulk of sensors. Therefore, this data is usually simulated to obtain results that validate different CP solutions. Although that is valid, real-world experimental data can, due to generally unpredictable nature (e.g., multipath, random reduction of measurement quality due to used sensors), indicate some issues with CP that simulated data may not. In this paper, a smaller scale measurement campaign for collecting CP data is described in detail. The benefit of this is the availability of real-world data for algorithm validation with the compromise of having a smaller test area. The measurements were collected in September 2018 in Sydney, Australia, for four pedestrians which were equipped with GNSS receivers, Ultra-Wide Band (UWB) radios and Wireless Ad-hoc System for Positioning (WASP) units. Local Positioning System (LPS) anchors equipped with WASP and UWB units were set up around the data collection area. Experiment design, setup, execution, quality assessment of the data and recommendations for future data collections are presented in the paper. In addition to this, to quantify the performance of the collected data, a comparison of multi-sensor fusion (GPS and local positioning system) and standalone GPS solution for each user is made. Further, integrity availability is assessed for standalone GPS and multi-sensor fusion solution. The performance is assessed under different conditions (e.g., static or dynamic pedestrians, data under the influence of multipath or with the open sky).

ABSTRACT. The integration of the GPS/INS system has been intensively investigated as it can provide long-term high-accuracy and robust navigation solution. In normal operation, either GPS pseudorange or carrier phase observations are fused with INS to satisfy different accuracy levels. Although a high precision positioning can be obtained by the double differencing carrier phase, it is still suffering from several drawbacks such as delays that can disrupt real-time integer ambiguity resolution and the length of the baseline. Over the past decade, the time-differenced carrier phase technique was employed to achieve high precision positioning without being involved in the differential procedures. However, the obtained positioning by the time-differenced carrier phase technique is still a relative positioning. This is because the positioning at the current epoch is dependent on the previous epochs and thus they are physically correlated. In some situations when an outlier occurs at an epoch, the subsequent epochs may include all the deteriorations which in turn cause unreliable positioning. This is because the positioning at the current epoch will suffer from the physical correlation between observations and also the correlation between fault test statistics. The current study employs the reliability theory for the detection and identification of multiple simultaneous faults when GPS time-differenced carrier phase observations are fused with INS. The correlation will be designed in correspondence with the number of faults in the observations. When multiple faults exist in the observations, the correlation is expanded from one- dimensional to multi-dimensional space. In other words, the correlation is between two vectors and each vector includes a group of measurements. The group of measurements coincides with the number of faults. The outcomes of this study will provide a foundation for improving quality control when the GPS time-differenced carrier phase observations are integrated with INS. This is can be achieved through checking potential faults at every observation spatially and temporarily.

ABSTRACT. Swarm of Unmanned Aerial Vehicles(UAVs) have been proven to be an efficient system in many fields and applications, such as disaster rescue, mapping and search. A crucial prerequisite for these applications is that UAVs can access to their global or relative locations. Currently, the main technique is GPS which may be inaccessible in many areas, such as forests, and indoor. Under this case, UAVs should be able to implement self-localization using on-board sensors. In this research, we consider a distributed cooperative positioning algorithm by using ultra-wideband(UWB). First, noise distribution of ultra wideband(UWB) is investigated which is essential for cooperative localization algorithm. Both of Line-of-sight(LOS) and Non-line-of-sight(NLOS) cases are considered. Three different distributions, Skewed student distribution, Mixture Gaussian and Gaussian, are used to fit the noise obtained from UWB device. The histograms of fitting results and related Kullback–Leibler divergence(KLD) are given to justify the the goodness of fit. Then, based on the fitted distribution, a distributed cooperative positioning algorithm is presented by using variational message passing(VMP) method. An efficient approximation is derived in order to reduce the communication and computational burden for resource-limited on-board UAVs. The simulation results demonstrate the efficiency of the algorithm.