Chris Rizos

Chris Rizos
UNSW Sydney | UNSW · School of Civil and Environmental Engineering

PhD (UNSW) 1980

About

697
Publications
301,979
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
12,839
Citations
Additional affiliations
January 1990 - present
UNSW Sydney
Position
  • Professor of Geodesy & Navigation

Publications

Publications (697)
Article
Full-text available
A new GNSS/IMU tightly coupled positioning system is introduced to train positioning. To fulfil a train control system’s aim of reducing the need to install trackside equipment, the GNSS precise point positioning (PPP) method is applied in place of the conventional differential GNSS method. As the railway environment has the character of long opera...
Article
Full-text available
A large percentage of the Costa Rican territory is covered with high evergreen forests. In order to compute a 1″ Bare-Earth Digital Terrain Model (DTM) for Costa Rica CRDTM2020, stochastic Vegetation Bias (VB) was reduced from the 1″ NASADEM, Digital Elevation Model (DEM) based on the Shuttle Radar Topography Mission (SRTM) data. Several global mod...
Conference Paper
In recent years, mega-constellation Low Earth Orbit (LEO) satellites have been proposed as an augmentation to the Global Navigation Satellite System (GNSS) for positioning on the ground, especially for those in measurement environments with limited satellite visibility. The fast geometry change of these LEO satellites also reduces the convergence t...
Article
Full-text available
Due to an increasing requirement for high accuracy orbital information for low Earth orbit (LEO) satellites, precise orbit determination (POD) of LEO satellites is a topic of growing interest. To assure the safety and reliability of the applications requiring high accuracy LEO orbits in near-real-time, integrity monitoring (IM) is an essential oper...
Article
Full-text available
The implementation of Intelligent Transport System (ITS) technology is expected to significantly improve road safety and traffic efficiency. One of the key components of ITS is precise vehicle positioning. Positioning with decimetre to sub-metre accuracy is a fundamental capability for self-driving, and other automated applications. Global Navigati...
Article
GNSS/INS integrated navigation and positioning technology is widely used and currently ideal for train operations seeking a decrease in dependence on trackside equipment. However, during train operations, environmental factors such as bridges, tunnels, hillsides, and buildings will block the satellite signals. When INS works in a stand-alone mode,...
Article
In 2017, the new generation satellite-based augmentation system (SBAS) test-bed was initiated by Australia and New Zealand, which supports the dual-frequency multi-constellation (DFMC) positioning with both GPS and Galileo signals. This new SBAS DFMC service allows the elimination of the first-order term of the ionospheric delays, and extends the s...
Conference Paper
Reliable ambiguity resolution is the key to obtaining centimetre-level accuracy in high precision GNSS positioning techniques such as Real-Time Kinematic (RTK) and Precise Point Positioning (PPP). In this contribution, an approach for partial ambiguity resolution based on the best integer equivariant estimator using the multivariant t-distribution...
Article
A key prerequisite for fast and reliable solution convergence time in precise point positioning with ambiguity resolution is the successful determination of the initial integer ambiguity parameters. In this contribution, a reliable approach of partial ambiguity resolution based on the BIE using the t-distribution (BIE-td) is proposed and compared a...
Article
Based on the unifying framework of the detection, identification and adaption (DIA) estimators, quality control indices are refined and formulated by taking the uncertainty of the combined estimation-testing procedure into account and performing the propagation of uncertainty. These indices are used to measure the confidence levels of the testing d...
Chapter
This chapter is organized into three parts. The first part is an introduction to space geodesy, the principles of global navigation satellite system (GNSS) geodesy, and the International Association of Geodesy (IAG). The IAG is the scientific association that organizes the space geodetic services that support high‐accuracy GNSS positioning for scie...
Article
Train integrity resolution is an important part of a train operation control system. In current train operation control systems, train integrity resolution is achieved by using information on the track circuit or the wind pressure. However, both approaches have limitations; the utilization of the track circuits requires high construction and mainte...
Article
Vehicular communication using the DSRC (Dedicated Short Range Communication) standard is becoming an enabling factor for a wide range of Cooperative Intelligent Transportation System (C-ITS) applications, especially those with high requirements of safety assurance. The location information of connected vehicles is fundamental, and significant for e...
Technical Report
Full-text available
This monthly newsletter is intended to keep IUGG Members and individual scientists informed about the activities of the Union, its Associations and interdisciplinary bodies, and the actions of the IUGG Secretariat, Bureau, and Executive Committee. Past issues are posted on the IUGG website. E-Journals may be forwarded to those who will benefit from...
Article
Full-text available
GPS precise point positioning (PPP) is increasingly being used in many precise positioning applications to achieve sub-meter level accuracy using a stand-alone user receiver. To achieve the full-scale navigation parameters of position, velocity and attitude, GPS is often combined with the inertial navigation system (INS) to deliver navigation solut...
Article
Full-text available
first_pagesettings Open AccessArticle Integrity Monitoring for Horizontal RTK Positioning: New Weighting Model and Overbounding CDF in Open-Sky and Suburban Scenarios by Kan Wang 1,*OrcID,Ahmed El-Mowafy 1,Chris Rizos 2OrcID andJinling Wang 2OrcID 1 School of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia...
Article
Global Navigation Satellite System Reflectometry (GNSS-R) altimetry uses GNSS-reflected signals off a water body to measure the height of the reflecting surface. The maximum value of the leading-edge derivative (LED) is an important path delay estimator in GNSS-R altimetry. The LED assumes that the weight function representing the power contributio...
Conference Paper
A major limitation of the GNSS Precise Point Positioning (PPP) technique is the slow solution convergence time. Tens of minutes are required for the solutions to converge to decimetre-level accuracy even with ambiguity resolution (PPP-AR). This paper analyses two ambiguity resolution methods to provide reliable ambiguity resolution and fast PPP con...
Article
Full-text available
Global Navigation Satellite System (GNSS) reflected signals can be used to remotely sense the Earth’s surface, known as GNSS reflectometry (GNSS-R). The GNSS-R technique has been applied to numerous areas, such as the retrieval of wind speed, and the detection of Earth surface objects. This work proposes a new application of GNSS-R, namely to detec...
Article
Dilution of precision (DOP) for time-of-arrival (TOA) or time-difference-of-arrival (TDOA) positioning systems has been thoroughly investigated. This is not the case for angle-of-arrival (AOA) positioning systems, especially three dimensional AOA systems. However, the recent increase in deployment of antenna arrays and multipath mitigation techniqu...
Article
The authors investigate the benefits for the precise point positioning (PPP) ambiguity resolution technique of using the GPS L1, L2 and L5; Galileo E1, E5a, E5b and E6; and BeiDou B1, B2 and B3 measurements. Data from 17 reference stations over a period of 31 consecutive days in 2018 were used. It was found that the four-frequency Galileo combinati...
Article
We assess the time-to-first-fix (TTFF) and the ambiguity fixing rate of two PPP wide-lane ambiguity resolution (WL-AR) methods, namely the geometry-based and ionospheric-free (GB-IF) method, and the geometry-free and ionospheric-free (GF-IF) method. First, an optimal GF-IF WL linear combination is selected based on the ratio between the code and ca...
Article
Full-text available
High-precision single-receiver positioning requires the provision of reliable network-derived corrections. Care must therefore be exercised to continuously check the quality of the corrections and to detect the possible presence of mis-modeled biases in the network data. In network-RTK or its state-space implementation, PPP-RTK, quality control of...
Article
It is a challenge to achieve high accuracy altimetric results using space-based global navigation satellite system reflectometry (GNSS-R). This paper focuses on improving the accuracy of space-based GNSS-R altimetric measurements by considering receiver dynamics in the geometric model. The receiver dynamics has negligible impact on the geometric mo...
Article
Airborne-Pseudolite (A-PL) systems have been proposed to augment Global Navigation Satellite Systems (GNSSs) in difficult areas where GNSS-only navigation cannot be guaranteed due to signal blockages, signal jamming, etc. One of the challenges in realising such a system is to determine the coordinates of the A-PLs to a high accuracy. The GNSS Preci...
Article
Full-text available
Global Navigation Satellite System (GNSS) is the most widely used Positioning, Navigation, and Timing (PNT) technology in the world today, but it suffers some major constraints. Locata is a terrestrial PNT technology that can be considered as a type of localised “constellation”, which is able to provide high-accuracy PNT coverage where GNSS cannot...
Article
Full-text available
We propose an optimal ionospheric-free linear combination (LC) model for dual- and triple-frequency PPP which can accelerate carrier phase ambiguity and decrease the position solution convergence time. To reduce computational complexity, a near-optimal LC model for triple-frequency PPP is also proposed. The uncombined observation (UC) model estimat...
Article
The BeiDou Navigation Satellite System (BDS) has been widely applied in many areas, including communications, transportation, emergency rescue, public security, surveying, precise positioning, and many other industrial applications. The integration of BDS and an Inertial Navigation System (INS) has the ability to achieve a more consistent and accur...
Article
Full-text available
Benefiting from multi-constellation Global Navigation Satellite Systems (GNSS), more and more visible satellites can be used to improve user positioning performance. However, due to limited tracking receiver channels and power consumption, and other issues, it may be not possible, or desirable, to use all satellites in view for positioning. The opt...
Article
Full-text available
The integration of Global Navigation Satellite System (GNSS) and Inertial Navigation System (INS) technologies is a very useful navigation option for high-accuracy positioning in many applications. However, its performance is still limited by GNSS satellite availability and satellite geometry. To address such limitations, a non-GNSS-based positioni...
Chapter
Full-text available
To achieve the best performance for a Kalman filter (KF) for global navigation satellite system (GNSS) positioning, a comprehensive measurement model is required. However, the GNSS observations suffer from unmodelled errors resulting from multipath, interference, etc. These errors are difficult (even impossible) to model using parametric models. In...
Conference Paper
Full-text available
As Intelligent Transport Systems (ITS) become more automated and more demanding, ITS positioning integrity is becoming a key performance parameter. ITS relies on GNSS technology for absolute positioning. In order to develop efficient models and methods that can provide high levels of integrity, it is necessary to study the vulnerabilities of the GN...
Chapter
This chapter presents an alternative framework to the traditional centralised Kalman filtering (CKF) approach for implementing the optimal state estimation algorithm in support of multisensor integration. The data fusion algorithm is implemented via a series of transformations of vectors in the so-called information space (iSpace). This chapter des...
Conference Paper
Full-text available
GNSS Network Real Time Kinematic (NRTK) has become a common service for many precise positioning applications over the last two decades. However, NRTK cannot service or support user applications if they are outside the Continuously Operating Reference Stations (CORS) network coverage area, such as in the case of offshore surveying. In addition, NRT...
Article
Full-text available
We describe an integrated navigation system based on Global Navigation Satellite Systems (GNSS), an Inertial Navigation System (INS) and terrestrial ranging technologies that can support accurate and seamless indoor-outdoor positioning. To overcome severe multipath disturbance in indoor environments, Locata technology is used in this navigation sys...
Article
Full-text available
We provided an overview of various satellite-based augmentation systems (SBAS) options for augmented GNSS services in Australia, and potentially New Zealand, with the aim to tease out key similarities and differences in their augmentation capabilities. SBAS can technically be classified into two user categories, namely SBAS for aviation and “non-av...
Article
Full-text available
Stochastic models are important in Global Navigation Satellite System (GNSS) estimation problems, not only for parameter estimation, or precision assessment, but also for deriving system reliability and integrity measures. China’s Beidou GNSS (BDS) has received considerable research attention, however it has mainly focused on parameter estimation c...
Article
Space-based Global Navigation Satellite System Reflectometry (GNSS-R) altimetry remains an open challenge. This paper reports on space-based GNSS-R altimetry using 40-s period of intermediate frequency recording from the TechDemoSat-1 mission. This recording is unique because one GPS signal is reflected from ice. The waveforms that are used to dete...
Article
Full-text available
Minimal detectable bias (MDB) describes a system's general ability to detect the existence of a single outlier. However, successful identification probability is closely related to the correlations between w-statistics. When the correlation is high, the validity of the MDB as a system internal reliability index is weakened. Based on the correlation...
Article
This paper presents an investigation into the performance of real-time Global Navigation Satellite Systems (GNSS) Precise Point Positioning (PPP) in New Zealand. The motivation of the research is to evaluate the feasibility of using PPP technique and a satellite based augmentation system such as the Japanese Quasi-Zenith Satellite System (QZSS) to...
Article
Full-text available
Within the last decade, GNSS Precise Point Positioning (PPP) has generated unprecedented interest among the GNSS community and is being used for a number of scientific and commercial applications today. Similar to the conventional relative positioning technique, PPP could provide positioning solutions at centimeter-level precision by making use of...
Chapter
Full-text available
As GNSS point-positioning becomes more precise and accessible to a wider spectrum of users, the issue of misalignment between GNSS positioning reference frames and spatial data reference frames used in GIS will become more apparent. Positions of plate-fixed features within GNSS reference frames are kinematic in nature due to global plate motions an...
Chapter
The Global Positioning System (GPS ) became available as a civilian geodetic survey technology in the early 1980s. It has since revolutionized not only geodesy, but surveying operations as well. Global Navigation Systems (GNSS s) are today a fundamental tool for the land, engineering, and hydrographic surveyor. The majority of GNSS survey tasks rel...
Conference Paper
Full-text available
GNSS Network Real-Time-Kinematic (NRTK) has become a common service for many precise positioning applications over the last two decades. However, NRTK cannot service or support user applications if they are outside the Continuously Operating Reference Stations (CORS) network coverage area, such as in the case of offshore surveying. In addition, NRT...
Conference Paper
An Inertial Navigation System (INS) is self-contained, immune to jamming/interference and in many other ways is ideally for pedestrian navigation applications especially in indoor environments. However, due to the sensor properties the quality of the navigation solution from a stand-alone INS will degrade rapidly, and must rely on some form of exte...
Article
Full-text available
The accuracy of Kalman filtering (KF) relies on the quality of the observations as well as the dynamic model. However, the dynamic model is usually assumed to be invariant, which is not realistic in real global navigation satellite system (GNSS) navigation applications due to unexpected vehicular motion. A new algorithm is proposed to enhance the K...
Article
An improvement of the attitude difference method (ADM) to estimate deflections of the vertical (DOV) in real time is described in this paper. The ADM without offline processing estimates the DOV with a limited accuracy due to the response delay. The proposed model selection-based self-adaptive delay feedback (SDF) method takes the results of the AD...
Article
Full-text available
On August 17th 1999, a Mw 7.4 earthquake struck the city of Izmit in the north-west of Turkey. This event was one of the most devastating earthquakes of the twentieth century. The epicentre of the Izmit earthquake was on the North Anatolian Fault (NAF) which is one of the most active right-lateral strike-slip faults on earth. However, this earthqua...
Article
Full-text available
On August 17<sup>th</sup> 1999, a M<sub>w</sub> 7.4 earthquake struck the city of Izmit in the north-west of Turkey. This event was one of the most devastating earthquakes of the twentieth century. The epicentre of the Izmit earthquake was on the North Anatolian Fault (NAF) which is one of the most active right-lateral strike-slip faults on earth....
Article
This paper describes an adaptive fault-tolerant multisensor integrated navigation system. The proposed system uses a decentralized filtering architecture to fuse inertial navigation system (INS), GNSS, and Locata sensor subsystems. In order to improve system accuracy, the global optimal filtering (GOF) algorithm is implemented. The GNSS and Locata...
Article
The performance of navigation sensors may be seriously affected by the operating rotors of a drone. To address this kind of disturbance , a low-cost multisensor integrated navigation system was developed for a quadrotor aerial vehicle (QAV). The navigation board integrates a global positioning system (GPS) module, triaxial gyroscope, accelerometer,...
Article
Full-text available
Various types of biases in Global Navigation Satellite System (GNSS) data preclude integer ambiguity fixing and degrade solution accuracy when not being corrected during precise point positioning (PPP). In this contribution, these biases are first reviewed, including satellite and receiver hardware biases, differential code biases, differential pha...
Article
Full-text available
Experts share views on issues and challenges of GNSS education
Conference Paper
Full-text available
South East Asia is growing at an impressive pace as its GDP increased about 350% in ten years passing from about 650 Billion $ in 2002 to about 2300 Billion $ in 2012. Regional governments actively promote infrastructure, logistics and service development to create a favourable environment for a sustainable growth. Within this framework, GNSS appli...
Article
Full-text available
Precise sound speed profile (SSP) information is critical when using sonar for underwater terrain navigation. Nevertheless, acquiring SSP information in real-time is difficult, especially in underwater navigation environment. To account for this problem, this paper presents an underwater navigation method, which applies real-time SSP correction to...
Article
Full-text available
A good port management system must be able to perform safe, predictable, and efficient execution of transport processes. In order to improve the quality of the port management, a robust navigation system is required, which enables to provide the positions of vessels 24/7 on either open or impeded environment. This paper describes a robust georefere...