Search

The benefits of an increased number of global navigation satellite systems (GNSS) in space have been confirmed for the robustness and convergence time of standard precise point positioning (PPP) solutions, as well as improved accuracy when (most of) the ambiguities are fixed. Yet, it is still worthwhile to investigate fast and high-precision GNSS parameter estimation to meet user needs. This contribution focuses on integer ambiguity resolution-enabled Precise Point Positioning (PPP-RTK) in the use of the observations from four global navigation systems, i.e., GPS (Global Positioning System), Galileo (European Global Navigation Satellite System), BDS (Chinese BeiDou Navigation Satellite System), and GLONASS (Global’naya Navigatsionnaya Sputnikova Sistema). An undifferenced and uncombined PPP-RTK model is implemented for which the satellite clock and phase bias corrections are computed from the data processing of a group of stations in a network and then provided to users to help them achieve integer ambiguity resolution on a single receiver by calibrating the satellite phase biases. The dataset is recorded in a local area of the GNSS network of the Netherlands, in which 12 stations are regarded as the reference to generate the corresponding corrections and 21 as the users to assess the performance of the multi-GNSS PPP-RTK in both kinematic and static positioning mode. The results show that the root-mean-square (RMS) errors of the ambiguity float solutions can achieve the same accuracy level of the ambiguity fixed solutions after convergence. The combined GNSS cases, on the contrary, reduce the horizontal RMS of GPS alone with 2 cm level to GPS + Galileo/GPS + Galileo + BDS/GPS + Galileo + BDS + GLONASS with 1 cm level. The convergence time benefits from both multi-GNSS and fixing ambiguities, and the performances of the ambiguity fixed solution are comparable to those of the multi-GNSS ambiguity float solutions. For instance, the convergence time of GPS alone amb, Mathematical Geodesy and Positioning

To be able to receive a position from a smartphone user is very valuable. Wit- hout this many applications would not work at all. For many applications the existing position libraries are not good enough, for example augmented reality applications which requires millimeter precision for a good experience. The goal of this report is to study if GNSS positioning can be improved for smartphones.The study focuses mostly on Android and has the goal of using the method “trilateration” to combine multiple satellites position and their distance to a receiver in order to calculate a real position. The projekt consists of two parts: and Android application and a Java Tomcat server. The android applica- tion uses the programming library “Location” to access raw GNSS-data for cal- culating the distance between the receiver and the satellites, which is called “pseudorange”, and the server functions as a REST API which provides GALI- LEO satellites current position. The project tries to combine these parameters in the Application to create a position. Although the report did not succeed in com- bining these parameters to calculate a position, it does describe of it is still pos- sible; which applications has succeeded before and what others ought to think about when starting similar studies. This project would require a bit more time to reach its end goal, but the fact that raw GNSS-data has become available to all developers on Android is a promising development since others may conti- nue or do their own research. This project focuses solely on GALILEO satelli- tes, mostly to time constraints. In future works all available satellite constella- tions should be used for better results., Att få en position av en smartphoneanvändare är mycket användbart, utan detta skulle många applikationer inte fungera alls. För många applikationer är den givna positionerings biblioteken inte tillräckligt bra dock, som t.ex. för augmen- ted reality applikationer som kräver millimeter-säker precision för en bra an- vändarupplevelse. Målet med denna rapport är att undersöka om GNSS-positio- nering kan förbättras inom smartphones. Undersökningen fokuserar mest på Android och har som målsättning att använda metoden “trilateration” för att kombinera satelliternas position och dess distans till en mottagare för att sedan räkna ut en verklig position. Projektet består av två delar: en Android applika- tion och en Java TomCat server. Android applikationen använder programme- rings biblioteket “Location” för att få tag på rå GNSS-data för att räkna ut di- stansen mellan satelliter och mottagaren, vilket kallas för “pseudorange”, och servern fungerar som ett REST API som returnerar GALILEO-satelliters nuva- rande position. Applikationen försöker kombinera pseudorange och satelliter- nas position med trilateration för at få ut mottagarens position. Rapporten lyck- as inte uppnå detta mål dock, men den beskriver hur det ändå är möjligt, vilka andra applikationer som lyckats och vad andra bör tänka på om de vill göra lik- nande studier. Det skulle behövas lite mer tid för att avsluta detta projekt, men faktumet att råa GNSS-data har blivit tillgänglig för alla Android-utvecklare, från att ha varit helt gömd, är en lovande utveckling då det låter andra forska på egen hand. Detta projekt fokuserar enbart på GALILEO satelliter, mestadels för tidsbegränsningar.

Positioning techniques made lots of progress in the last decades, thanks to the wide usage of the Global Navigation Satellite Systems (GNSS). During a satellite survey, interruption or complete absence of positioning service can happen due to obstacle presence or constrained environments. To avoid these problems, it is suitable to simulate a positioning survey determining the number of the GNSS satellites in view and their availability trend for a selected location. Using more than one constellation the number of the observed satellites is increased and the continuity and reliability of positioning significantly improved. The aim of this paper is to assess the impact of multi-GNSS constellation on positioning calculation in terms of number of available satellites and geometrical distribution in the sky. A simulation is conducted for different cut-off angles, ranging from 0° to 30°: satellites visibility predictions are performed for the city of Benevento (Italy) using short observing sessions (96 daily) and considering GPS, GLONASS and GALILEO constellation. The benefits of their combinations are investigated: in order to assess the observation quality, the Geometrical Dilution of Precision (GDOP) is used as criteria to prove how it is possible to reduce degradation of the position accuracy by using multi-GNSS combinations. Particularly, GPS+GLONASS supplies higher performances compared to the other solutions. Because the low number of satellites in view, the contribution of GALILEO is limited, and its presence instead of GPS or GLONASS in the two constellation solutions produces a decrease in positioning accuracy.

This paper summarizes studies on the utilization of precise clock synchronization in satellite-based navigation and communication. The user's clock synchronization with one of the precise clocks installed in a navigation satellite or ground radio station, which maintains the time standard for the generation of range measurement signals, enables the adoption of new satellite navigation concepts, and the simplicity will open up avenues for efficient methods of mobile communications. Precise clock synchronization between two radio stations, which really means the detection of the time offset between two clocks, is performed, in principle, by using bi-directional communication between these stations and by detecting the difference in radio propagation times between one direction and its opposite. Satellite positioning based on clock synchronization will reduce the number of deployed satellites and mitigate geometrical requirements for satellite placement. Application of synchronized timing to spread-spectrum communications will produce a technology combining Code Division Multiple Access (CDMA) with Time Division Multiple Access (TDMA), with which optional communications between radio stations and multiple access circuit control for mobile message communications can be achieved efficiently. Another subject of this paper is the formulation and integration of several kinds of satellite-based navigation algorithms. Such formation and integration can be skillfully achieved by applying the Weight Least Squares (WLS) method. Nearly optimal estimation of positioning is done by regulating the weights of the WLS algorithm, referring to the numerical values of Dilution Of Precision (DOP), which are calculated from the covariance matrix of the position error discussed in this paper. Characteristics of the WLS navigation algorithm are discussed in relation to the geometry of satellite placement., 本論文では、衛星利用航法と無線局間の精密クロック同期を用いた通信の研究についてまとめた。ユーザの時計を、航法衛星あるいは地上無線局に設置され距離測定信号を生成するための標準時間を与えている精密時計と同期させることは、新しい衛星航法を採用することを可能とし、これらの航法の単純性は、より有効な移動体通信法の開拓に路を開くものである。無線局間の双方向通信を用いて、1つの方向とその反対方向への電波伝播時間の違いを検出することにより、2つの無線局間の、実際には2つの時計間の時間オフセットの検出を意味する精密クロック同期を行った。クロック同期に基づいた衛星位置決定は、配備する衛星の数を減らし、また衛星の配置に対する要求を軽減するであろう。また、同期タイミングのスペクトル拡散通信への応用は、時分割多元接続(TDMA)と符号分割多重接続(CDMA)とを結合する技術を可能にするであろう。この技術によって、無線局間の任意の通信と移動メッセージ通信のための多元接続回路制御を、効率よく達成することができる。この論文のもう1つの主題は、数種類の衛星利用航法アルゴリズムの形式化と統合についてある。このような形式化と統合は、重み付き最小2乗(WLS)法を用いることで、うまく行うことができる。ここでは、WLSアルゴリズムでの重みを正規化し、本論文中で議論した位置ベクトルエラーの共分散行列から計算したDOP(希釈度)の数値と照らし合わせることによって、位置決定のほぼ最適な推定を行った。WLS航法アルゴリズムの性質を、衛星の配置と関連付けて議論した。

An orbit that lies on a Kolmogorov, Arnold, and Moser (KAM) Torus will remain on that torus until and unless it experiences a force that causes it to leave the torus. Earth satellites that are subject only to the Earth's gravity field may lie on such KAM tori. Analyzing on orbit satellite position data should allow for the identification of the fundamental frequencies needed to define the KAM tori for modeling Earth satellite orbits. KAM Tori are created for the Gravity Recovery and Climate Experience (GRACE) and Jason-1 satellites to model their orbital motion. Precise position data for the satellites is analyzed using a modified Laskar frequency algorithm to determine the fundamental frequencies of the orbits. The fundamental frequencies along with a set of Fourier coefficients completely describe the tori. These tori are then compared to the precise orbital position data for the satellites to determine how well they model the orbits. The KAM torus created for the Jason-1 satellite is able to represent the position of the satellites to within 1 km. Further refinement of the torus should be possible, resulting in a more accurate model of the orbit. The GRACE torus was less successful at determining the satellite positions. Atmospheric drag cannot be ignored at the altitude where GRACE flies. It may still be possible to model GRACE with a KAM torus by applying perturbation theory to the torus; however, further research is needed to confirm this., The original document contains color images.

Thus far, solutions for distance based road user charging have typically been based on the road owner's requirements rather than those of the road users. As the techniques employed to measure road usage gets more sophisticated, for example by using satellite positioning, end user privacy is increasingly challenged. Road owners deciding on system design have to prioritize between many requirements competing for resources, and when doing so privacy is an early candidate to stand back. This paper argues that this is unnecessary, and that respect for privacy can be kept intact, without making any concessions on requirements for cost of ownership, ability to effectively enforce non compliant vehicles, or competitive system procurement. Portions of a charging concept with high privacy standards tested by the Oregon Department of Transport is here adapted and expanded to fit regulations and typical requirements from several European cases, presenting a holistic charging scheme., QC 20141002

Purpose: To validate a nondifferential global positioning system (GPS) to measure speed, displacement, and position during human locomotion. Methods: Three healthy participants walked and ran over straight and curved courses for 59 and 34 trials, respectively. A nondifferential GPS receiver provided speed data by Doppler shift and change in GPS position over time, which were compared with actual speeds determined by chronometry. Displacement data from the GPS were compared with a surveyed 100-m section, and static positions were collected for 1 h and compared with the known geodetic point. Results: GPS speed values on the straight course were closely correlated with actual speeds (Doppler shift: r = 0.9994, P G 0.001, $ GPS position/time: r = 0.9984, P G 0.001). Actual speed errors were lowest using the Doppler shift method (90.8% of values within T 0.1 mIsj1). Speed was slightly underestimated on a curved path, though still highly correlated with actual speed (Doppler shift: r = 0.9985, P G 0.001, $ GPS distance/time: r = 0.9973, P G 0.001). Distance measured by GPS was 100.46 T 0.49 m, and 86.5% of static points were within 1.5 m of the actual geodetic point (mean error: 1.08 T 0.34 m, range 0.69– 2.10 m). Conclusions: Nondifferential GPS demonstrated a highly accurate estimation of speed across a wide range of human locomotion velocities using only the raw signal data with a minimal decrease in accuracy around bends. This high level of resolution was matched by accurate displacement and position data. Coupled with reduced size, cost, and ease of use, this method offers a valid alternative to differential GPS in the study of overground locomotion.

GPS signals can be used for positioning satellites in geostationary (GEO) orbits, but the performance in this case is poor, because very few pseudorange measurements are available at any given time. This paper describes a new method for improving geostationary satellite navigation accuracy by using dynamic Two-Way Time Transfer (TWTT) measurements. By directly measuring the clock error between the GPS satellite and the GPS receiver, TWTT allows meaningful information to be gathered when less than four GPS satellites are available. A simulation was developed in which satellites in GEO orbits with GPS receivers onboard generated a position with 1) GPS with a crystal clock, 2) GPS with an onboard atomic clock, 3) GPS with TWTT to a ground-based atomic clock, and 4) GPS with TWTT to a ground-based clock synchronized to GPS time. Bringing an atomic clock into the system (Cases 2 and 3) resulted in a 21-38% improvement in the 3-D RMS position accuracy over the standard GPS case (Case 1). However, using TWTT with a clocked slaved to GPS time resulted in a 60%-70% improvement in 3-D RMS positioning accuracy. This level of performance was obtained for TWTT measurement error standard deviations anywhere between 0.3 ns to 30 ns., Presented at the Annual Precise Time and Time Interval (PTTI) Meeting (39th) held in Long Beach, CA on 26-29 Nov 2007. Published in the Proceedings of the Annual Precise Time and Time Interval (PTTI) Meeting (39th), p511-530, 2007. The original document contains color images.

A Bread Board Model of a spaceborne hydrogen maser atomic clock for the satellite positioning system using Quasi-Zenith Satellites has been developed. Analysis and experiments for technical problems such as miniaturization, achievement of long life, mechanical vibration proofing, and space environment characteristics have been performed, and technical data necessary for EM development have been obtained., See also ADM001784. Presented at the Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting (36th) held in Washington, DC on 7-9 Dec 2004. Published in the Proceedings of the Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting (36th), p423-430, 2004. The original document contains color images.

In (Teunissen, 2003) we introduced the class of integer aperture (IA) estimators. This class is larger than the class of integer (I) estimators, but smaller than the class of integer equivariant (IE) estimators. The IA-estimator is of a hybrid nature since its outcome may be integer-valued or real-valued. For its probabilistic evaluation one needs to take both the success-rate and fail-rate into account, since these two probabilities do not sum up to one as it is the case with integer estimators. The IA-estimators also take care of the so-called discernibility problem of GNSS ambiguity resolution. In the present contribution we will introduce one particular integer aperture estimator, the ellipsoidal IA-estimator. This estimator has the advantage that a rigorous and easy-to-evaluate probabilistic description of its performance can be given. It will also be shown that some well-known discernibility tests which are used in practice are in fact examples of IA-estimators.

GNSS carrier phase ambiguity resolution is the key to fast and high-precision satellite positioning and navigation. It applies to a great variety of current and future models of GPS, modernized GPS and Galileo. In (Teunissen, 1998, 1999) we introduced the class of admissible integer (I) estimators and showed that the integer least-squares estimator is the optimal ambiguity estimator within this class. In (Teunissen, 2002a, b) we introduced the class of integer equivariant (IE) estimators and determined the best ambiguity estimator within this class. This best integer equivariant estimator is unbiased and of minimum variance. In the present contribution we will introduce a third class of ambiguity estimators. This class of integer aperture (IA) estimators is larger than the I-class, but smaller than the IE-class. The IA-estimator is of a hybrid nature since its outcome may be integer-valued or real-valued. We also give a probabilistic description of IA-estimators. This is needed in order to be able to propagate the inherent uncertainty in the data rigorously and to give a proper probabilistic evaluation of the final result. The framework of IA-estimation also incorporates the important problem of ambiguity discernibility. By setting the size and shape of the integer aperture pull-in region of an IA-estimator, the user has control over the fail-rate of the estimator and thus also over the amount of discernibility.

This thesis investigates the design, implementation and validation of a multi-antenna GPS system to monitor the displacement of deforming slopes. The system utilises a switched antenna array design allowing data from multiple antennas to be sampled sequentially by one GPS receiver. The system provides quasi-continuous GPS observations that can produce a precise and reliable coordinate time-series of the movement of the slope under consideration. GPS observations and particularly those concerned with the monitoring of steep slopes, are subject to systematic errors that can significantly degrade the quality of the processed position solutions. As such, this research characterises the data in terms of multipath effects, the spectrum of the coordinate time-series, and the carrier to noise power density ratio of the raw GPS observations. Various GPS processing parameters are then investigated to determine optimal processing parameters to improve the precision of the resulting coordinate time-series. Results from data stacking techniques that rely on the daily correlation of the repeating multipath signature find that the GPS data actually decorrelates somewhat from day to day. This can reduce the effectiveness of stacking techniques for the high precision monitoring of steep slopes. Finally, advanced stochastic models such as elevation angle and carrier-to-noise weighting are investigated to optimise the precision of the coordinate time-series data. A new in-line stochastic model is developed based on weighting GPS observations with respect to the level of systematic error present within the data. By using these advanced types of stochastic models, reductions to the noise level of the coordinate time-series of approximately 20 and 25 percent are possible in the horizontal and height components respectively.Results from an extensive field trial of this system on a deforming high-wall of an open-pit mine indicate that approximately 135mm of displacement occurred over the 1

The World Geodetic System 1984 (WGS 84) Earth Gravitational Model (EGM) consists of a set of normalized geopotential coefficients complete through degree (n) and order (m) 180. The first part of the EGM, through degree and order 41, was developed as a weighted least squares combination solution from mean free-air gravity anomalies; geoid undulations derived from satellite radar altimetry; laser, Doppler and NAVSTAR Global Positioning System (GPS) satellite tracking data and 'lumped coefficient' data. Procedures used in the EGM development, testing and evaluation are discussed with particular emphasis on orbital analysis results as they apply to Doppler point positioning. Keywords: Geodesy; Earth gravitational models; Satellite positioning., Presented at International Geodetic Symposium on Satellite Positioning (4th), Austin, TX 28 Apr-2 May 86.

The NAVSTAR Global Positioning System (GPS) has been under development by the US Department of Defense since 1973. Although GPS was developed for precise instantaneous position and velocity determination, it can be used for high precision relative positioning, with numerous applications for both surveyors and geodesists. The high resolution of the satellite's carrier phase has enabled relative positioning accuracies of the order of one part per million to be routinely obtained, from only one or two hours of data. These accuracies are obtained using the broadcast ephemeris, which is the orbit data that is broadcast in the satellite's radio transmission. However, the broadcast ephemeris is estimated to be in error by up to twenty five metres and this error is one of the principle limitations for precise relative positioning with GPS. An alternative to the broadcast ephemeris, is to determine the satellite orbits using the carrier phase measurements, obtained from a network of GPS tracking stations. This thesis describes the algorithms and processing techniques used for the determination of GPS satellite orbits using double differenced carrier phase measurements. The data from three different GPS campaigns have been analysed, which demonstrate a GPS orbital accuracy of between two and four metres, giving baseline accuracies of the order of one or two parts in ten million.

The NAVSTAR Global Positioning System (GPS) has been under development by the US Department of Defense since 1973. Although GPS was developed for precise instantaneous position and velocity determination, it can be used for high precision relative positioning, with numerous applications for both surveyors and geodesists. The high resolution of the satellite's carrier phase has enabled relative positioning accuracies of the order of one part per million to be routinely obtained, from only one or two hours of data. These accuracies are obtained using the broadcast ephemeris, which is the orbit data that is broadcast in the satellite's radio transmission. However, the broadcast ephemeris is estimated to be in error by up to twenty five metres and this error is one of the principle limitations for precise relative positioning with GPS. An alternative to the broadcast ephemeris, is to determine the satellite orbits using the carrier phase measurements, obtained from a network of GPS tracking stations. This thesis describes the algorithms and processing techniques used for the determination of GPS satellite orbits using double differenced carrier phase measurements. The data from three different GPS campaigns have been analysed, which demonstrate a GPS orbital accuracy of between two and four metres, giving baseline accuracies of the order of one or two parts in ten million.