Dilution Of Precision Research Articles

Accuracy Of The GPS Positioning System In The Context Of Increasing The Number Of Satellites In The Constellation

Abstract A possibility of utilising the GPS system for navigation and transport are fundamentally dependent on the accuracy in positioning. Two fundamental factors decisive for its value are the values of the User Range Error (URE) and Dilution of Precision (DOP), strictly related to the number of satellites forming the constellation. The nominal constellation of GPS satellites consists of 24 units which gives a possibility of identification of coordinates all over the globe. In the last few years, however, the nominal number of satellites in the constellation was much higher, and the URE value has been constantly increasing. The authors of the paper try to estimate the impact of the changing number of GPS satellites on accuracy of position coordinates with a variable URE value. Mathematical model for estimating geometrical indicators’ value, utilising data derived from the almanac files has been presented. Following a drawn-up algorithm and calculations made with Mathcad software, the authors carried out a comparative analysis of mean daily values of DOP indicators for a variable number of satellites included in the GPS constellation in the years 2001-2013. Then, the authors have established representative values of Two Distance Root Mean Square Error (2drms) 2D and 3D, and calculated a percentage increase of accuracy in the period under discussion.

Evaluation of Multi-GNSSs and GPS with 3D Map Methods for Pedestrian Positioning in an Urban Canyon Environment

Highly accurate pedestrian position information is required in many applications, especially in automatic driving system. Global Positioning System (GPS) developed by American has proven itself reliability in most of the environments. Unfortunately, urban areas contain the signal reflection, known as multipath and non-line-of-sight (NLOS) effects. In addition, the lake of line-of-sight (LOS) satellites caused by the blockage of skyscrapers also severely degrades the accuracy and availability of the GPS positioning. To solve these problems, a solution that interoperated several Global Navigation Satellite Systems (GNSSs) is proposed. However, the actual difficulty of satellite positioning in urban area is the distorted satellite distribution. This paper proposes a GPS with 3D map ray tracing positioning method to conquer the difficulty. The proposed method takes the advantage of the non-LOS (NLOS) and uses it as an additional measurement. Significantly, these measurements are sourced from the satellites that should be blocked. Thus, the dilution of precision (DOP) can be greatly improved. To verify the performance of the proposed method, real data is collected at Tokyo urban area. This paper compares the performance of GPS/GLONASS and the proposed GPS with 3D map ray tracing methods. The results reveals the proposed method is capable of identifying which side of street the pedestrian stands and the GPS+GLONASS method is not.

IEEE 802.11 RSSI 기반 무인비행로봇 실내측위를 위한 AP 선택 기법

Abstract: As required performance of UAV (Unmanned Aerial Vehicle) becomes more complex and complicated, required positioning accuracy is becoming more and more higher. GPS is a reliable world wide positioning providing system. Therefore, UAV generally acquires position information from GPS. But when GPS is not available such as too weak signal or too less GPS satellites environments, UAV needs alternative positioning system such as network positioning system. RSSI (Received Signal Strength Indicator) based positioning, which is one method of network positioning technologies, determines its position using RSSI measurements containing distance information from AP (Access Point)s. In that method, a selected AP's configuration has strong and tight relationship with its positioning errors. In this paper, for, we additionally account AP's configuration information by adopting DOP (Dilution of Precision) into AP selection procedures and provide more accurate RSSI based positioning results.Keywords: indoor positioning, DOP, RSSI

Locata Network Design and Reliability Analysis for Harbour Positioning

To meet the accuracy, integrity, continuity and availability required for many navigation applications the Locata technology can provide an alternative to satellite-based navigation in difficult Global Navigation Satellite System (GNSS) signal environments, especially for applications in port areas and in constricted waterways. Unlike GNSS constellations, a LocataNet – a local constellation of LocataLites – can be designed specifically for different environments to avoid signal blockages, interference or poor geometry. By using Locata technology, the optimal performance within particular areas can always be guaranteed. This paper demonstrates the influence of LocataNet configuration on the reliability and integrity of the Locata positioning system. The performance of the Locata system is investigated using the Receiver Autonomous Integrity Monitoring (RAIM) concept. Fault Detection and Exclusion (FDE) algorithm performance is validated through the computation of the Dilution of Precision (DOP), the Horizontal Protection Level (HPL) and the correlation coefficient between two failure modes that can indicate the quality of fault identification. The experimental analysis shows that a good configuration of LocataLites will enhance the accuracy and reliability of the navigation system.

Global Positioning System (GPS) Positioning Errors During Ionospheric Scintillation Event

As technology advancement progresses throughout the years in this modern age, every technology has its part to play in that the world is moving towards a brighter future. GPS (Global Positioning System) has diverse application in current globalized world, its application has pervasive benefits not only to navigation and positioning, it is pivotal in industries like logistics, shipping, financial services and agriculture. Since the decision to shut down the Selectivity Availability (SA) by former U.S. President, Bill Clinton, ionospheric effect is now the primary concern of error contributing factors in GPS. Ionospheric scintillation induces rapid fluctuations in the phase and the amplitude of received Global Navigation Satellite System (GNSS) signals. These rapid fluctuations or scintillation potentially introduce cycle slips, degrade range measurements, and if severe enough lead to loss of lock in phase and code. Global Ionospheric Scintillation Model (GISM) was used to compute amplitude scintillation parameter for each GPS satellite visible from Melaka, Malaysia (Latitude 20 14’ N, Longitude 1020 16’ E) as its location has strong equatorial scintillation behavior. The output data from GISM was then used to calculate the positioning error where it is depends on the Dilution of Precision (DOP) and User Equivalent Range Error (UERE). There are two schemes that were used. First, the positioning error was calculated for all the visible satellites with better DOP but worse UERE due to scintillation event. Secondly, the positioning error was calculated for those satellites that have amplitude scintillation index, S4 < 0.7 which leads to worse DOP with better UERE. Comparison of results from the both schemes was then made.

Analytical quality assessment of iteratively reweighted least-squares (IRLS) method

The iteratively reweighted least-squares (IRLS) technique has been widely employed in geodetic and geophysical literature. The reliability measures are important diagnostic tools for inferring the strength of the model validation. An exact analytical method is adopted to obtain insights on how much iterative reweighting can affect the quality indicators. Theoretical analyses and numerical results show that, when the downweighting procedure is performed, (1) the precision, all kinds of dilution of precision (DOP) metrics and the minimal detectable bias (MDB) will become larger; (2) the variations of the bias-to-noise ratio (BNR) are involved, and (3) all these results coincide with those obtained by the first-order approximation method.

GNSS Multipath and Jamming Mitigation Using High-Mask-Angle Antennas and Multiple Constellations

Multipath and jamming interference affects the accuracy, availability, and continuity of global navigation satellite systems. The U.S. Global Positioning System and the Russian Global'naya Navigatsionnaya Sputnikovaya Sistema (GLONASS) are being joined by the European Galileo and the Chinese BeiDou. An increasing number of satellites in multiple constellations enable users to use high-mask-angle antennas (HMAAs) to mitigate interference signals coming from a low-elevation angle. This paper studies the optimal antenna mask angle that maximizes the suppression of interference but still maintains the performance of a single constellation with a low-mask-angle antenna. This paper first proves a novel lower bound on the expectation of dilution of precision (DOP) and derives closed-form formulas that relate the lower bound to the antenna mask angle and the number of satellites. Then, through extensive simulations, a variety of optimal mask angles are obtained with respect to different constellation settings, different DOP metrics, and different assumptions of range accuracy. The numerical results highly agree with our theory. Both of them show that two constellations can match the performance of one constellation with a 5 $^{\circ}$ –14 $^{\circ} $ higher mask, and three constellations can match the performance of one constellation with an 11 $^{\circ}$ –23 $^{\circ} $ higher mask, depending on the DOP metric and the range error model used. The numerical results also show that using HMAAs is more beneficial to users interested in positioning accuracy than to users interested in time transfer accuracy.

GPS 전파교란원 위치 추정을 위한 TDOA/AOA 복합 기법 설계

For a localization system, the TDOA (Time Difference of Arrival) measurement and AOA (Angle of Arrival) measurement are often used for estimating target’s positions. Although it is known that the accuracy of TDOA based localization is superior to that of AOA based one, it may have a poor vertical accuracy in bad geometrical conditions. This paper, therefore, proposes a localization algorithm in which the vertical position is estimated by AOA measurements and the horizontal one is estimated by TDOA measurement in order to achieve high 3D-location accuracy. And this algorithm is applied to a GPS jammer localization systems because it has a large value of the DOP (Dilution of Precision) when the jammer is located far away from the system. Simulation results demonstrate that the proposed hybrid TDOA/AOA location algorithm gives much higher location accuracy than TDOA or AOA only location.

Geometrical distortion integrated performance index for vision-based navigation system

This paper proposes weighted dilution of precision (WDOP) as an indicator of the accuracy of position and attitude in vision-based navigation. WDOP accurately represents the tendencies of navigational errors. It is obtained by weighted least squares. The weight is determined by the deployment of feature points and the geometrical distortion of the vision sensor. The performance of WDOP was verified by simulation. The values of the dilution of precision (DOP) and WDOP were computed and analyzed by comparison with the navigational errors. Additionally, a correlation test was used to determine how well they reflect the trends of the navigational errors. Simulation results showed that WDOP was strongly correlated with navigational errors, which makes it a parameter that can be used to determine the quality of a vision-based navigation system. The proposed WDOP can be used as a practical indicator of navigation performance.

SMP2-based Architecture for Navigation Satellite System Simulation

The Performance Simulation for the Global Navigation Satellite System (GNSS), which can be used in the performance simulation and evaluation analysis of the Service Volume Segment of the GNSS is a part of the critical algorithm test and system index analysis for the GNSS. In this article, the requirements and features of the GNSS are analyzed firstly, and the method of performance simulation for the GNSS is studied. Then, the system operation architecture and model integration architecture based on compassable simulation based on Simulation Model Portability (SMP2) is proposed. The system architecture consists of model design, development, integrating, executing and analysis, and can be used in simulation for diffe rent types of analyses such as those on visibility, coverage, geometry, Dilution of Precision (DOP), Navigation System Performance (NSP), and the availability and continuity of the Navigation System. Finally, the regional performance of the GALILEO Navigation Satellite System in China is analyzed based on the architecture and method, which can fit the features and satisfy the requirements of GN SS simulation.

Assessment Models and Rules of GNSS Interoperability

Global Navigation Satellite System (GNSS) interoperability could make use of the information from different navigation satellite systems. To estimate GNSS interoperability at the system level, an innovative assessment algorithm was presented in this paper. First of all, three assessment parameters, namely, Dilution Of Precision (DOP), Navigation Satellite System Precision (NSSP) and Navigation Satellite System Integrity (NSSI) were introduced. Secondly, availability and continuity of the assessment parameters were adopted to quantify the GNSS performance. A further step was then taken to focus on the assessment rule for GNSS performance by employing the weighted sum of availability and continuity. Simulation results demonstrate that GNSS performance could be improved significantly by interoperability.

Digital Surface Models for GNSS Mission Planning in Critical Environments

AbstractGlobal Navigation Satellite System (GNSS) surveys performed in critical environments (e.g., urban canyons, mountainous areas, or areas of dense vegetation) usually suffer from a lack of satellite coverage as a result of obstacles such as buildings and vegetation. GNSS mission-planning software provides an estimate of satellite visibility and dilution-of-precision (DOP) values along a planned trajectory to establish the best time frame over which to perform the survey. However, such an estimate is not reliable in a complex scenario because the surrounding environmental morphology is not considered. This paper introduces a new method to improve the prediction of GNSS satellite visibility. This method involves computing GNSS satellites position by means of the orbital parameters, as well as using three-dimensional digital surface models (DSMs) to develop a more reliable mission plan. The time evolution of key parameters describing the GNSS constellation is computed by means of a visibility georeferen...

AP 상대위치 정보를 고려한 향상된 WLAN RSSI 기반 실내 측위 알고리즘

With the development of mobile internet, requirements of positioning accuracy for the LBS (Location Based Service) are becoming more and more higher. The LBS is based on the position of each mobile device. So, it requires a proper acquisition of accurate user's indoor position. Thus indoor positioning technology and its accuracy is crucial for various LBS. In general, RSSI (Received Signal Strength Indicator) measurements are used to obtain the position information of mobile unit under WLAN environment. However, indoor positioning error increases as multiple AP's configurations are becoming more complex. To overcome this problem, an enhanced indoor localization method by AP (Access Point) selection criteria adopting DOP (Dilution of Precision) is proposed.

육상교통환경 위성항법 성능 예측을 위한 Sky-View-Factor 기반 Dilution of Precision 분석

위성항법의 가시성, Dilution of Precision (DOP), 신호대잡음비 등과 같은 위치결정 성능지표는 개활지 환경과 같이 항법위성의 가시성이 좋은 지역에서 그 활용도가 높으며, 육상교통환경의 경우 그 활용도가 낮다. 본 논문은 육상교통환경에서 위성항법 신호를 활용하여 위치결정을 수행하는 경우 활용도가 높은 성능지표로 Sky View based DOP (SVDOP)을 제안한다. SVDOP은 Sky-View Factor(SVF)를 응용하여 개발되었으며, 기존의 SVF의 문제점을 극복할 수 있다. Sky-View 영상을 활용하여 특징점을 선택하고 이를 활용하여 DOP를 계산할 수 있다. 제안된 방법을 이용하는 경우 SVF 사용보다 육상교통환경에서 위치결정 성능 예측에 용이함을 확인할 수 있다. The conventional indexes for describing the GNSS positioning performance such as satellite visibility, dilution of precision (DOP) and signal to noise ratio is very useful in open sky, however, they are not useful in the land road environment. In this paper new index is suggested for describing the GNSS positioning performance for the road environment. The new index is called Sky View based DOP (SVDOP). SVDOP is derived referring the Sky-View-Factor (SVF). The usefulness is analyzed by comparing the SVDOP and SVF in land road environment after the singularity points are selected and SVDOP is calculated.

Weighted DOP With Consideration on Elevation-Dependent Range Errors of GNSS Satellites

This paper proposes the weighted dilution of precision (WDOP) with consideration of the satellite elevation angle in order to improve the performance of dilution of precision (DOP), which is a standard tool to quantify the positional precision of the Global Navigation Satellite System (GNSS). The WDOP is calculated by assigning different weights to visible GNSS satellites depending on their elevation angles. In order to demonstrate the effectiveness of WDOP, the conventional DOP and WDOP were mathematically analyzed and a comparative analysis was conducted using actual Global Positioning System data. Results showed that WDOP represents the position error trends more accurate than the conventional DOP, particularly when low-elevation measurements were used for positioning calculation. Therefore, the WDOP could be a promising replacement of DOP as a tool for representing and quantifying errors in GNSS positioning.

위성항법시스템기반의 위치오차에 관한 연구

본 논문은 위성항법시스템을 이용한 정밀 단독측위에 관한 연구이다. 위성항법시스템이 가지고 있는 내재적인 문제점인 장애물 등 여러 가지 환경 요인으로 인해 신호를 수신할 수 없는 경우 음영지역과 위치오차 증가 등에 관한 연구논문이다. 논문에서는 다양한 수신기의 성능 분석과 대도로 중앙, 대도로 측면, 주택가, 고층 건물 주변의 골목길 등 다양한 환경에 따른 위성수와 DOP(Dilution of Precision) 변화 그리고 위치오차의 변화 등을 분석하였다. 그리고 환경 변화에 따른 위치오차 발생 범위와 오차 원인을 파악하여, 위성항법시스템의 신뢰성과 안정성을 높이는데 그 목적이 있다.

DOP prediction over Egypt from SP3 file for long-term

An important error source in satellite surveying deals with the geometry of the visible satellite constellation at the time of observation. This is similar to the situation in traditional surveys, where the geometry of the network of observed ground stations affects the accuracies of computed positions. Dilution of precision (DOP) is an indicator of the quality of the geometry of the visible satellite constellation. The value of DOP is very important during observation sessions, because many projects have special requirements regarding the positioning accuracy. These special requirements will force the surveyor to hold the survey mission until the value of dilution of precision at the time of observation meets the project’s requirements. This means that the GPS mission planning is an essential task before any GPS survey. The task of this paper is related to The GPS mission planning which the values of dilution of precisions and number of visible satellites should be predicted for the observation points, this task should determine the best observation periods which meet the project requirements. This paper explore the process of DOP prediction for long term by using Standard Product 3 (SP3) file and attempt to mathematically or statistically bound the navigation error. In this paper the actual orbital period of GPS satellite was defined and the DOP contour map over Egypt was constructed. By using these contour maps one can predict the DOP by knowing the city name.

New method of GPS orbit determination from GCPS network for the purpose of DOP calculations

The accuracy of GPS measurement satisfies the requirements of some applications, but many applications require an improvement of GPS measurement accuracy. For precise positioning by GPS, it is necessary to perform GPS mission planning. The GPS mission planning is a pre-survey task in which the values of Dilution Of Precision (DOP) should be predicted for the observation points, this task should determine the best observation periods which meet the project requirements. The main purpose of this work is to study a rather simple but still fairly accurate algorithm to determine the artificial satellite orbits for the purpose of DOP calculation. The orbit determination algorithm proposed in this paper is implemented by using several reference stations and calculated the orbits by new algorithm; inverse GPS. Inverse GPS means that reference stations are considered as satellites and satellite as receiver. This new algorithm used to calculate the satellite orbit which is mainly used to calculate the DOP. A comparison is done between the estimated PDOP by using satellite coordinates from new method and from the SP3 (Standard Product # 3) file.

Novel Method for Wind Estimation Using Automatic Dependent Surveillance-Broadcast

TWOmethods to acquire near real-time wind information can be distinguished [1–5]. The first method uses wind observations made by aircraft systems that are relayed to the ground. The second uses secondary surveillance radar (SSR) position and speed data, possibly extendedwith downlink airborne parameters (DAPs).When DAPs are unavailable, the SSR’s position and speed data can be used to estimate wind from aircraft that completed a turn [3,4]. This paper presents a novel method to estimate wind using Automatic Dependent Surveillance-Broadcast (ADS-B) over a larger area. ADS-B-equipped aircraft broadcast their position, ground speed, track angle, and other aircraft information [6,7]. Although registers for data in the air reference frame exist, data analysis showed these are left unused by most aircraft. For wind estimation purposes, ADS-B provides velocity vector information measured using a global satellite navigation system. This information can also be derived from SSR position data. However, the latter are expected to be, in most cases, less accurate and have a lower update rate. Previous methods were based on a single aircraft and therefore required multiple measurements of that aircraft at different headings. The proposed approach is new as it circumvents this limitation by assuming that aircraft at the same altitude travel, on average, at the same true airspeed (TAS) in all directions. The remainder of this note is organized as follows. Section II discusses the theoretical model and the application of dilution of precision (DOP) and Kalman filtering techniques to integrate noisy wind estimates into a time-varying wind profile for a larger area. Section III discusses the results of simulations to assess the effect of the actual wind speed and airspeed differences between aircraft. Section IV gives the results of a comparative analysis of wind estimates made using actual ADS-B datawith forecasts of the Global Forecast System (GFS). II. Wind Estimation Algorithm

Generalised DOPs with Consideration of the Influence Function of Signal-in-Space Errors

Integrated navigation using multiple Global Navigation Satellite Systems (GNSS) is beneficial to increase the number of observable satellites, alleviate the effects of systematic errors and improve the accuracy of positioning, navigation and timing (PNT). When multiple constellations and multiple frequency measurements are employed, the functional and stochastic models as well as the estimation principle for PNT may be different. Therefore, the commonly used definition of “dilution of precision (DOP)” based on the least squares (LS) estimation and unified functional and stochastic models will be not applicable anymore. In this paper, three types of generalised DOPs are defined. The first type of generalised DOP is based on the error influence function (IF) of pseudo-ranges that reflects the geometry strength of the measurements, error magnitude and the estimation risk criteria. When the least squares estimation is used, the first type of generalised DOP is identical to the one commonly used. In order to define the first type of generalised DOP, an IF of signal–in-space (SIS) errors on the parameter estimates of PNT is derived. The second type of generalised DOP is defined based on the functional model with additional systematic parameters induced by the compatibility and interoperability problems among different GNSS systems. The third type of generalised DOP is defined based on Bayesian estimation in which the a priori information of the model parameters is taken into account. This is suitable for evaluating the precision of kinematic positioning or navigation. Different types of generalised DOPs are suitable for different PNT scenarios and an example for the calculation of these DOPs for multi-GNSS systems including GPS, GLONASS, Compass and Galileo is given. New observation equations of Compass and GLONASS that may contain additional parameters for interoperability are specifically investigated. It shows that if the interoperability of multi-GNSS is not fulfilled, the increased number of satellites will not significantly reduce the generalised DOP value. Furthermore, the outlying measurements will not change the original DOP, but will change the first type of generalised DOP which includes a robust error IF. A priori information of the model parameters will also reduce the DOP.