Sunil Bisnath

York University · Department of Earth and Space Science and Engineering (Lassonde School of Engineering)

The Galileo High Accuracy Service (HAS) is a GNSS augmentation that provides precise satellite corrections to users worldwide for free directly through Galileo’s E6 signal. The HAS service provides free PPP corrections from the Galileo constellation and the Internet, with targeted real-time 95% positioning performance of better than 20 cm horizonta...

Precise positioning using smartphones has been a topic of interest especially after Google decided to provide raw GNSS measurement through their Android platform. Currently, the greatest limitations in precise positioning with smartphone Global Navigation Satellite System (GNSS) sensors are the quality and availability of satellite-to-smartphone ra...

The European Union H2020 grant project “GISCAD-OV” (Galileo Improved Services for Cadastral Augmentation Development On-field Validation) involves the whole cadastral surveying value chain. The project’s purpose is to design, develop and validate an innovative and cost-effective high accuracy service for cadastral surveying applications, based on G...

The Global Navigation Satellite System (GNSS) capability in smartphones has seen significant upgrades over the years. The latest ultra-low-cost GNSS receivers are capable of carrier-phase tracking and multi-constellation, dual-frequency signal reception. However, due to the limitations of these ultra-low-cost receivers and antennas, smartphone GNSS...

The full operational capability of the Chinese BeiDou Satellite Navigation System (BDS) has injected additional energy into the GNSS field. Along with the visibility of more BDS satellites, as well as the precise products generated by analysis centers, Precise Point Positioning (PPP) float and fixed ambiguity performance with the complete BDS const...

Smartphones typically compute position using duty-cycled Global Navigation Satellite System (GNSS) L1 code measurements and Single Point Positioning (SPP) processing with the aid of cellular and other measurements. This internal positioning solution has an accuracy of several tens to hundreds of meters in realistic environments (handheld, vehicle d...

Precise Point Positioning (PPP), as a global precise positioning technique, suffers from relatively long convergence times, hindering its ability to be the default precise positioning technique. Reducing the PPP convergence time is a must to reach global precise positions, and doing so in a few minutes to seconds can be achieved thanks to the addit...

The proliferation of low-cost GNSS hardware smartphones providing multi-constellation, multi-frequency carrier-phase and pseudorange measurements for the Android platform offer an avenue for Precise Point Positioning (PPP) GNSS use in recent years. However, smartphone PPP is restricted due to high multipath effects and signal loss leading to metre-...

This paper describes a computation method for obtaining dielectric constant using Global Navigation Satellite System reflectometry (GNSS-R) products. Dielectric constant is a crucial component in the soil moisture retrieval process using reflected GNSS signals. The reflectivity for circular polarized signals is combined with the dielectric constant...

Precise point positioning (PPP) has proved its capacity to provide centimetre-level position solutions in open sky environments. However, the technique still suffers from relatively long initial convergence times. Research has proved the potential of ambiguity resolution (AR) to reduce the convergence time and three main methods are used to perform...

Due to its nature, Precise Point Positioning (PPP) depends on the GNSS measurements and quality of satellite correction products used to relatively quickly provide precise and accurate positions. With the rapid evolution of Global Navigation Satellite Systems (GNSSs), new frequencies and signals are being broadcast, which have a positive impact on...

Precise Point Positioning (PPP) has undergone significant changes since its conception over 20 years ago. Advances in specific areas such as ambiguity resolution, the use of external ionospheric data and the addition of new GNSS constellations and signal frequencies have produced great improvements. In this research, we try to aim to obtain RTK per...

This chapter describes the concepts and theory involved in relative global navigation satellite system (GNSS) positioning and navigation. It begins by describing the concepts and advantages of relative positioning in contrast to point positioning, and the conceptual and terminological similarities and differences between differential and relative p...

Global Navigation Satellite Systems (GNSS) have been undergoing major changes recently. While old constellations are getting modernized, new ones are being completed. These developments mean that more satellites than ever are in orbit and broadcasting GNSS signals. This ever-increasing number of satellites is naturally having major effects on the p...

The Global Navigation Satellite System (GNSS) Precise Point Positioning (PPP) technology benefits from not needing local ground infrastructure such as reference stations and accuracy attained is at the decimetre-level, which approaches real-time kinematic (RTK) performance. However, due to its long position solution initialization period and comple...

This study evaluates the feasibility of achieving improved positioning accuracy with raw GNSS measurements from recently released smartphones. Using Precise Point Positioning (PPP) as the processing mode, positioning accuracy of selected newly available devices are analyzed. These devices include Xiaomi Mi8, Google Pixel 3, Huawei Mate 20 and Samsu...

In this paper, a new standard that has been developed by Sapcorda Services to target the specific requirements of high‐precision GNSS technology in the automotive and mass market industry is assessed within the context of existing data standards. This new standard was created as a joint effort of several organizations and has similarities with the...

GNSS positioning performance has been shown to improve with the ingestion of data from Global Ionospheric Maps (GIMs) and tropospheric zenith path delays, which are produced by, e.g., the International GNSS Service (IGS). For both dual- and triple-frequency Precise Point Positioning (PPP) processing, the significance of GIM and tropospheric product...

In the past few years, the number of applications for GNSS has grown dramatically. As a result of this progression, the requirements for GNSS positioning systems have also changed. One of the most relevant components in precision GNSS technology is the correction data format or standard used to transmit corrections from reference GNSS infrastructur...

With an increase in the number of satellite systems, redundant measurements, and improved satellite orbit and clock products, the initial convergence period of dual-frequency GNSS Precise Point Positioning (PPP) borders on tens of minutes to achieve an accuracy of a few centimetres. However, dual-frequency PPP still remains impractical for many rea...

Few decimetre to metre level accuracy is possible using the cellphone grade GNSS hardware. Current low-cost and ultra-low-cost (cellphone) GNSS receivers have no dual-frequency observables to form linear combination, in-order to account for the ionospheric delay. Global Ionospheric Maps (GIM) are used to mitigate the ionospheric error. Signal-to-no...

The general objective of this study is to analyze the performance of Precise Point Positioning (PPP) convergence and initialization while stochastically constraining the atmosphere. One specific objective of this study is to review the performance of dual-and triple-frequency PPP solutions using uncombined measurements. The research question to be...

With the advent of quad-constellation, triple-frequency and external atmospheric constraints being provided to the PPP user, the novelty and focus of this paper is in the quest to answer the question: Do we really need ambiguity resolution in multi-GNSS PPP for accuracy or for integrity? To address the first component of the question, which is also...

Integer ambiguity resolution of carrier-phase measurements from a single receiver can be implemented by applying additional satellite corrections (products) to mitigate unmodelled satellite equipment delays. Interoperability of different PPP-AR products would allow the PPP user to transform independently generated PPP-AR products to obtain multiple...

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...

GLONASS pseudorange observations are affected by inter-frequency channel biases (ICBs) due to the frequency division multiple access (FDMA) satellite signal structure. This research estimated the GLONASS pseudorange inter-frequency channel biases using 350 IGS stations, based on 32 receiver types and over 11 antenna types over a period of 1 week, D...

While satellite clock combinations are routinely utilized within the IGS, they currently disregard the fact that some ACs provide integer clocks. Users have been expected to choose either a robust combined solution or select individual AC solutions that provide integer clocks allowing the user to compute a PPP-AR solution. The goal of our investiga...

A global navigation satellite system (GNSS) receiver processes signals transmitted from the satellites to determine user position, velocity, and time. Compared to conventional receivers, a software GNSS receiver offers better design flexibility and requires fewer dedicated hardware components [1]. An ideal software receiver typically processes all...

In large-area LiDAR mapping projects, surveyors might collect data at different times and with different sensors, creating loosely connected laser point clouds with varying point densities, accuracies, and overlaps. Current LiDAR calibration methodologies refine each point cloud and evaluate the accuracy of each point cloud individually. In the cas...

The Precise Point Positioning (PPP) GPS data processing technique has developed over the past 15 years to become a standard method for growing categories of positioning and navigation applications. The technique relies on single receiver point positioning combined with precise satellite orbit and clock information, pseudorange and carrier-phase obs...

Pseudorange multipath and pseudorange noise are the largest remaining unmanaged error sources in PPP. It is proposed that by reducing the effects of multipath and noise on the pseudorange observable, accurate estimates of carrier phase float ambiguities will be attained sooner, thus reducing the initial convergence period of PPP. Given the problem,...

Unlike GPS, GLONASS observations are affected by the Frequency Division Multiple Access (FDMA) satellite signal structure, which introduces inter-frequency channel biases (ICBs) and other system biases. The effects of these biases are visible in the pseudorange and carrier-phase residuals, which affect GNSS Precise Point Positioning (PPP) convergen...

Over the past decade, network RTK technology has become popular as an efficient method of precise, real-time positioning. Its relatively low-cost and single receiver ease-of-use has allowed it to mostly replace static relative GPS and single baseline RTK in urban areas where such networks are economically viable (e.g., cadastral and construction su...

The combination of GPS measurements and high-fidelity dynamic models via a Kalman filter/smoother, known as the reduced dynamic technique, allows 3D positioning of Low Earth Orbiters to the sub-decimeter level. Such accuracies can only be achieved if the GPS data are nearly continuous, post-processed and a dual-frequency receiver is utilized. The f...

While much research effort has been applied to improving the accuracy of GPS Precise Point Positioning (PPP) coordinate solutions and reducing the duration of data collection needed to achieve such accuracies, little work has been published on the integrity of PPP solutions. Integrity and monitoring are essential components of any positioning / nav...

In standard Precise Point Positioning (PPP), the carrier phase ambiguities are estimated as real-valued constants, so that the carrier-phases can provide similar information as the pseudoranges. As a consequence, it can take tens of minutes to several hours for the ambiguities to converge to suitably precise values. Recently, new processing methods...

Precise Point Positioning (PPP) has become a popular technique to process GNSS receiver data by applying precise satellite orbit and clock information, along with other minor corrections. Although PPP presents definite advantages such as operational flexibility and cost effectiveness for users, it requires tens of minutes for solution initializatio...

Constraining the ionosphere delay is the key step in rapid ambiguity resolution. Previous work has shown how PPP-AR re-convergence can be achieved by constraining internal ionosphere estimates. That method is extended here to permit rapid convergence using external ionospheric estimates from other PPP-AR solutions. Subject to the use of good orbits...

Ambiguity Resolution for Precise Point Positioning (PPP) is possible when the system hardware delays have been properly accounted for in the observation model. Even when the carrier phase ambiguity parameters are formally integer in nature however, there is still a substantial convergence period required before meaningful ambiguity resolution is po...

It has become a trend to replace the traditional single baseline RTK approach by using network RTK services, whilst there is still lack of authoritative guidelines and specifications with this most recent development of GNSS positioning. For this purpose, the Ministry of Transportation of Ontario (MTO), Canada is interested in the performance, as w...

This paper describes a method of processing Global Positioning System (GPS) observations to achieve undifferenced ambiguity resolution. Dual-frequency carrier phase and pseudorange measurements are processed by specifying separate oscillator parameters for the carrier phase and pseudorange measurements. Carrier phase estimates of the oscillator err...

The degradations in accuracy of GPS precise orbit determination solutions for Low Earth Orbiters (LEOs) are analyzed under various constraints in this study. The constrained solutions are compared against a reference solution that is determined by post-processing dual-frequency data from the CHAllenging Mini-Satellite Payload (CHAMP). The constrain...

Global positioning and navigation relies on Global Navigation Satellite Systems (GNSSs), the best known among these being the Global Positioning System (GPS), followed by the GLObal NAvigation Satellite System (GLONASS). With ongoing development of the Galileo and Compass satellite navigation systems, it appears that multi-GNSS data processing will...

The research discussed in this paper addresses the question of how to simulate realistic observables from current and pending Global Navigation Satellite Systems (GNSSs) in a way that is independent of the characteristics of specific systems. The generated observables can be used to predict future multi-GNSS performance and aid in the development o...

The precise point positioning (PPP) technique, which can be used for the processing of static and kinematics data, both in real time holds are powerful and promising future in the GPS industry. PPP is the state-space solution to the processing of pseudo range and carrier-phase measurements from a single GNSS receiver, utilizing satellite constellat...

The Geomatics Engineering program at York University, established in 2001, is one of four, four-year undergraduate geomatics engineering programs in Canada. The program was established to provide novel engineering studies and to address the increasing need for geomatics engineering education in Ontario. In this paper, we share the experiences gaine...

Various agencies around the world are looking at GPS to play a role in tsunami warning systems. The Geological Survey of Canada has begun a pilot project on Vancouver Island, using the Western Canada Deformation Array to determine co-seismic displacement from a real-time network solution. The Geodetic Survey Division is investigating whether real-t...

Geodetic data, interpreted in light of seismic imaging, seismicity, xenolith studies, and the late Quaternary geologic history of the northern Great Basin, suggest that a subcontinental-scale extensional detachment is localized near the Moho. To first order, seismic yielding in the upper crust at any given latitude in this region occurs via an M7 e...

The project on “Next-generation algorithms for navigation, geodesy and earth sciences under modernized Global Navigation Satellite Systems (GNSS)” has been under development within the scope of the Geomatics for Informed Decisions (GEOIDE) Network. The GEOIDE Network is part of the Networks of Centres of Excellence program (NCE) of the government o...

The Precise Point Positioning Working Group within the Next Generation RTK Sub-Commission of IAG Commission 4 has been involved with Precise Point Positioning (PPP) developments for the past few years. The information presented here summarizes the Working Group’s findings concerning the state of PPP technology, and discusses the probable near-term...

The Decoupled Clock Model is a reformulation of the ionosphere-free code and phase observation equations for GPS, which, when combined with the widelane-phase/narrowlane code observable, permits undifferenced ambiguity resolution of 86cm and 11cm ambiguities. The nature of the decoupled clock model implies a clock, or clock-like, parameter estimate...

Geodetically, postseismic deformation can be identified through the nonlinear curvature in the temporal time series of site position. The ability to identify postseismic deformation is therefore dependent upon geodetic accuracy, length of time series, the spatial pattern of the postseismic deformation, and the characteristics of the causative seism...

Dual-frequency, geodetic-quality GPS receivers are routinely used both in static and kinematic applications for high-accuracy point positioning. However, use of low-cost, single-frequency GPS receivers in similar applications creates a significant challenge because of how the measurement error sources are handled. In this paper, we examine the pote...

Transient tectonic deformation is well known to be localized on or within ~100 km of major plate boundary faults zones and active volcanic regions, and may be in the form of both seismic and episodic aseismic events. But given evidence for triggering phenomena and secular variations in strain release at 1000-km scale along diffuse plate boundaries...

In December of 2004, the University of Southern Mississippi (USM) deployed an ocean observing data buoy in the northern Gulf of Mexico. To facilitate the measurement of long-period vertical movement, such as tides, dual-frequency GPS receivers were installed on the buoy and at three shore stations. The shore stations were located at ranges of 20 km...

In December of 2004, the University of Southern Mississippi (USM) deployed an ocean observing data buoy in the northern Gulf of Mexico. To facilitate the measurement of long-period vertical movement, such as tides, dual-frequency GPS receivers were installed on the buoy and at three shore stations. The shore stations were located at ranges of 20 km...

Transient tectonic deformation has long been noted within approximately 100 km of plate boundary fault zones and within active volcanic regions, but it is unknown whether transient motions also occur at larger scales within plates. Relatively localized transients are known to occur as both seismic and episodic aseismic events, and are generally asc...

The horizontal position of the Slide Mountain site (SLID) of the Basin and Range Geodetic Network (BARGEN) has presented anomalously high horizontal variability since its construction in 1997. Its weighted root-mean-square east and north position components, relative to best-fit straight lines, are a factor of ~2 greater than surrounding BARGEN sit...

The University of Southern Mississippi (USM) and the University of New Brunswick (UNB) have collaborated to devise and carry out a long-term experiment in precise GPS positioning over long distances in a marine environment. A pair of GPS reference stations have been deployed on either side of the Bay of Fundy in Canada, at the terminals of an appro...

In recent years, Global Positioning System (GPS) receivers have been placed on buoys to determine sea surface height. The Naval Oceanographic Office (NAVOCEANO) has become interested in this application for tides work and has sponsored a series of GPS buoy experiments in Mississippi coastal waters. The primary goal of the experiments was the determ...

Summary A completely geometric approach for precise orbit determination (POD) of low earth orbiters (LEOs) is presented, which does not rely on dynamic models, but only data from a GPS receiver onboard a LEO and the International GPS Service (IGS) GPS orbit and clock products. Initial processing of CHAMP receiver data indicated measurement anomalie...

The goal of the research described in this paper is the design of a GPS data processing technique capable of producing high-precision positioning results, regardless of platform dynamics, utilizing only a single, high-quality receiver. This goal is accomplished by combining two processing philosophies: point positioning, which makes use of precise...