scholarly journals Evaluation of a Low Cost Hand Held Unit with GNSS Raw Data Capability and Comparison with an Android Smartphone

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4185 ◽  
Author(s):  
Gérard Lachapelle ◽  
Paul Gratton ◽  
Jamie Horrelt ◽  
Erica Lemieux ◽  
Ali Broumandan
Keyword(s):  
Carrier Phase ◽  
Low Cost ◽  
High Sensitivity ◽  
Measurement Noise ◽  
Single Frequency ◽  
Raw Data ◽  
Phase Measurements ◽  
Position Accuracy ◽  
Wide Range ◽  
Free Position

A newly available portable unit with GNSS raw data recording capability is assessed to determine static and kinematic position accuracy in various environments. This unit is the GPSMap 66, introduced by Garmin in early September. It is all-weather and robust for field use, and comes with a helix antenna. The high sensitivity chipset is capable of acquiring and tracking signals in highly attenuated environments. It can track single frequency GPS, GPS + GLONASS or GPS + Galileo and record code, Doppler and carrier phase data every second in the RINEX format. The evaluation presented herein focusses on GPS and Galileo. Static and kinematic test results obtained under a wide range of realistic field conditions are reported. Differential GNSS methods and Precise Point Positioning (PPP) are used to assess absolute position accuracy in ITRF coordinates, which is sufficiently close to the GPS and Galileo reference frame for the current purpose. Under low multipath conditions, measurements are found to be sufficiently accurate to provide single epoch, bias free position accuracy of a few metres. Accuracy is a function of signal attenuation and multipath conditions. The use of an external geodetic antenna significantly reduces measurement noise and multipath in high multipath environments. Carrier phase measurements, available more or less continuously under open sky conditions, significantly improve performance in differential mode. Accuracy in vehicular mode using code and carrier phase differential RTK solution is at the level of a few to several dm. Tests were conducted in parallel with a Huawei P10 Android 8.0 smartphone. The code measurement noise of this unit was found to be significantly higher than that of the GPSMap 66, a major reason being its lower performance PIFA antenna; carrier phase was only available for short time intervals, significantly degrading differential position accuracy performance.

scholarly journals Robust INS/SFPPP-BDS tightly coupled navigation algorithm with adaptive cycle slip compensation model

2019 ◽  
Vol 13 ◽  
pp. 174830181983304
Author(s):  
Hangshuai Ma ◽  
Rong Wang ◽  
Zhi Xiong ◽  
Jianye Liu ◽  
Chuanyi Li
Keyword(s):  
Navigation System ◽  
Carrier Phase ◽  
Low Cost ◽  
Integrated System ◽  
Single Frequency ◽  
Cycle Slip ◽  
Phase Measurements ◽  
Satellite Navigation System ◽  
Tightly Coupled ◽  
Robust Adaptive

The application of Beidou Satellite Navigation System (BDS) is developing rapidly. To satisfy the increasing demand for positioning performance, single-frequency precise point positioning (SFPPP) has been a focus in recent years. By introducing the SFPPP technique into the INS/BDS integrated system, higher navigation accuracy can be obtained. Cycle slip, which is caused by signal blockage during the measurement of the carrier phase, is a challenge for SFPPP application. In the INS/SFPPP-BDS integrated system, cycle slip can cause serious bias in BDS carrier phase measurements. In this paper, a new INS/SFBDS-PPP tightly coupled navigation system and a robust adaptive filtering method are proposed. Using a low-cost single-frequency receiver integrated with INS, an observation model was built based on the pseudo range and carrier phase by PPP preprocessing. The cycle slip was introduced into the state vector to improve the estimation precision. The test statistics, comprising the innovation and its covariance, were used to estimate the time at which cycle slip occurred and its amplitude to compensate for its effect on the observation. Finally, the proposed system model and algorithm are validated by simulation.

scholarly journals High accuracy positioning with low-cost single-frequency GPS system in multipath environments

2021 ◽  
Author(s):  
Abdulla Al-Naqbi
Keyword(s):  
Low Cost ◽  
Low Frequency ◽  
Ionospheric Delay ◽  
Measurement Noise ◽  
Single Frequency ◽  
International Gnss Service ◽  
Phase Measurements ◽  
Differential Positioning ◽  
The Difference ◽  
Gps System

Positioning using low-cost, single-frequency GPS receivers provides an economical solution, but these receivers are subject to biases leading to degradation of the accuracy required. Factors contributing to degradation in the accuracy of low-cost systems are ionospheric delay, multipath, and measurement noise. Unless carefully addressed, these errors distort the ambiguity resolution process, and result in less accurate positioning solutions. However, with the modern hardware improvements, measurement noise is now almost neglibible. Ionospheric delay has been dramatically reduced with the availablity of global or local ionospheric maps produced by various organizations (e.g., International GNSS Service (IGS), and National Oceanic and Atmospheric Administraion (NOAA). The major remaining constraint and challenging problem is multipath. This is because mulitpath is environmentally dependant, difficult to model mathematically, and cannot be reduced through differential positioning. The research proposes a new approach to identify multipath-contaminated L1 measurements. The approach is based on wavelet analysis using Daubechies family wavelets. First, the difference between the code and carrier phase measurements was estimated, leaving essentially twice the ionospheric delay, multipath and system noise. The ionospheric delay is largely removed by using high resolution ionospheric delay maps produced by NOAA. The remaining residuals contain mainly low-frequency multipath, if existed, and high-frequency part of the residual component described above. The L1 measurements obtaines from the staellites with lowest multipath were used to compute the final positions using Trimble Total Control (TTC) and Bernese scientific processing software packages. The AC12 single-frequency GPS receiver was extensively tested in static and kinematic modes. Accuracies within 5 cm was demostrated for baselines up to 65 km under various multipath environments.

scholarly journals Performance Comparison among Multi-GNSS Single Frequency Precise Point Positioning Techniques

2019 ◽  
Vol 18 (32) ◽  
pp. 80-99
Author(s):  
Anna Innac ◽  
Antonio Angrisano ◽  
Salvatore Gaglione ◽  
Mario Vultaggio ◽  
Nicola Crocetto
Keyword(s):  
Carrier Phase ◽  
Precise Point Positioning ◽  
A Priori ◽  
Performance Comparison ◽  
Single Frequency ◽  
Integer Number ◽  
Phase Measurements ◽  
Processing Strategies ◽  
Wide Range ◽  
Point Positioning

Precise Point Positioning (PPP) is a technique able to compute high accuracy positioning anywhere using a single GNSS receiver and without the need for corrections from reference stations. A wide range of possible PPP algorithms, using different correction models and processing strategies, exist for both post-processing and real-time applications. PPP relies on accurate satellite and clock data, with the use of precise carrier-phase measurements. Single Frequency-PPP (SF-PPP) is currently under investigation by the scientific community, owing to its cheap implementation with respect to classical differential positioning and multi-frequency un-differenced techniques. Unfortunately, the carrier-phase observable is ambiguous by an a priori unknown integer number of cycles, called ambiguity, which is difficult to resolve with SF receivers. The aim of this paper was to study the opportunity provided by the use of a multi-GNSS constellation applied to two widespread SF-PPP models, based on different carrier-phase and code observable combinations. The algorithms were tested using static data collection carried out in an open-sky scenario. The results show decimeter level accuracy on the horizontal and vertical components of the position.

scholarly journals High accuracy positioning with low-cost single-frequency GPS system in multipath environments

2021 ◽  
Author(s):  
Abdulla Al-Naqbi
Keyword(s):  
Low Cost ◽  
Low Frequency ◽  
Ionospheric Delay ◽  
Measurement Noise ◽  
Single Frequency ◽  
International Gnss Service ◽  
Phase Measurements ◽  
Differential Positioning ◽  
The Difference ◽  
Gps System

Positioning using low-cost, single-frequency GPS receivers provides an economical solution, but these receivers are subject to biases leading to degradation of the accuracy required. Factors contributing to degradation in the accuracy of low-cost systems are ionospheric delay, multipath, and measurement noise. Unless carefully addressed, these errors distort the ambiguity resolution process, and result in less accurate positioning solutions. However, with the modern hardware improvements, measurement noise is now almost neglibible. Ionospheric delay has been dramatically reduced with the availablity of global or local ionospheric maps produced by various organizations (e.g., International GNSS Service (IGS), and National Oceanic and Atmospheric Administraion (NOAA). The major remaining constraint and challenging problem is multipath. This is because mulitpath is environmentally dependant, difficult to model mathematically, and cannot be reduced through differential positioning. The research proposes a new approach to identify multipath-contaminated L1 measurements. The approach is based on wavelet analysis using Daubechies family wavelets. First, the difference between the code and carrier phase measurements was estimated, leaving essentially twice the ionospheric delay, multipath and system noise. The ionospheric delay is largely removed by using high resolution ionospheric delay maps produced by NOAA. The remaining residuals contain mainly low-frequency multipath, if existed, and high-frequency part of the residual component described above. The L1 measurements obtaines from the staellites with lowest multipath were used to compute the final positions using Trimble Total Control (TTC) and Bernese scientific processing software packages. The AC12 single-frequency GPS receiver was extensively tested in static and kinematic modes. Accuracies within 5 cm was demostrated for baselines up to 65 km under various multipath environments.

scholarly journals A Low-Cost, High-Precision Vehicle Navigation System for Deep Urban Multipath Environment Using TDCP Measurements

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3254 ◽  
Author(s):  
Jungbeom Kim ◽  
Minhuck Park ◽  
Yonghwan Bae ◽  
O-Jong Kim ◽  
Donguk Kim ◽  
...  
Keyword(s):  
High Precision ◽  
Navigation System ◽  
Carrier Phase ◽  
Low Cost ◽  
Integer Ambiguity ◽  
Single Frequency ◽  
Vehicle Navigation ◽  
Phase Measurements ◽  
Vehicle Navigation System ◽  
Multipath Errors

In this study, we developed a low-cost, high-precision vehicle navigation system for deep urban multipath environments using time-differenced carrier phase (TDCP) measurements. Although many studies are being conducted to navigate autonomous vehicles using the global positioning system (GPS), it is difficult to obtain accurate navigation solutions due to multipath errors in urban environments. Low-cost GPS receivers that determine the solution based on pseudorange measurements are vulnerable to multipath errors. We used carrier phase measurements that are more robust for multipath errors. Without correction information from reference stations, the limited information of a low-cost, single-frequency receiver makes it difficult to quickly and accurately determine integer ambiguity of carrier phase measurements. We used TDCP measurements to eliminate the need to determine integer ambiguity that is time-invariant and we combined TDCP-based GPS with an inertial navigation system to overcome deep urban multipath environments. Furthermore, we considered a cycle slip algorithm for its accuracy and a multi-constellation navigation system for its availability. The results of dynamic field tests in a deep urban area indicated that it could achieve horizontal accuracy of at the submeter level.

scholarly journals Improving DGNSS Performance through the Use of Network RTK Corrections

2021 ◽  
Vol 13 (9) ◽  
pp. 1621
Author(s):  
Duojie Weng ◽  
Shengyue Ji ◽  
Yangwei Lu ◽  
Wu Chen ◽  
Zhihua Li
Keyword(s):  
Carrier Phase ◽  
Local Area ◽  
Satellite System ◽  
High Accuracy ◽  
Single Frequency ◽  
Baseline Length ◽  
Low Latitude ◽  
Phase Measurements ◽  
Network Rtk ◽  
Global Navigation Satellite

The differential global navigation satellite system (DGNSS) is an enhancement system that is widely used to improve the accuracy of single-frequency receivers. However, distance-dependent errors are not considered in conventional DGNSS, and DGNSS accuracy decreases when baseline length increases. In network real-time kinematic (RTK) positioning, distance-dependent errors are accurately modelled to enable ambiguity resolution on the user side, and standard Radio Technical Commission for Maritime Services (RTCM) formats have also been developed to describe the spatial characteristics of distance-dependent errors. However, the network RTK service was mainly developed for carrier-phase measurements on professional user receivers. The purpose of this study was to modify the local-area DGNSS through the use of network RTK corrections. Distance-dependent errors can be reduced, and accuracy for a longer baseline length can be improved. The results in the low-latitude areas showed that the accuracy of the modified DGNSS could be improved by more than 50% for a 17.9 km baseline during solar active years. The method in this paper extends the use of available network RTK corrections with high accuracy to normal local-area DGNSS applications.

Reducing multipath effect of low-cost GNSS receivers for monitoring by considering temporal correlations

2020 ◽  
Vol 14 (2) ◽  
pp. 167-175
Author(s):  
Li Zhang ◽  
Volker Schwieger
Keyword(s):  
Low Cost ◽  
Ground Plane ◽  
Single Frequency ◽  
Spatial Correlations ◽  
Raw Data ◽  
Multipath Effect ◽  
Temporal Correlations ◽  
Multipath Effects ◽  
Gnss Receivers ◽  
Multipath Signals

AbstractThe investigations on low-cost single frequency GNSS receivers at the Institute of Engineering Geodesy (IIGS) show that u-blox GNSS receivers combined with low-cost antennas and self-constructed L1-optimized choke rings can reach an accuracy which almost meets the requirements of geodetic applications (see Zhang and Schwieger [25]). However, the quality (accuracy and reliability) of low-cost GNSS receiver data should still be improved, particularly in environments with obstructions. The multipath effects are a major error source for the short baselines. The ground plate or the choke ring ground plane can reduce the multipath signals from the horizontal reflector (e. g. ground). However, the shieldings cannot reduce the multipath signals from the vertical reflectors (e. g. walls).Because multipath effects are spatially and temporally correlated, an algorithm is developed for reducing the multipath effect by considering the spatial correlations of the adjoined stations (see Zhang and Schwieger [24]). In this paper, an algorithm based on the temporal correlations will be introduced. The developed algorithm is based on the periodic behavior of the estimated coordinates and not on carrier phase raw data, which is easy to use. Because, for the users, coordinates are more accessible than the raw data. The multipath effect can cause periodic oscillations but the periods change over time. Besides this, the multipath effect’s influence on the coordinates is a mixture of different multipath signals from different satellites and different reflectors. These two properties will be used to reduce the multipath effect. The algorithm runs in two steps and iteratively. Test measurements were carried out in a multipath intensive environment; the accuracies of the measurements are improved by about 50 % and the results can be delivered in near-real-time (in ca. 30 minutes), therefore the algorithm is suitable for structural health monitoring applications.

scholarly journals Real-time GNSS precise point positioning for low-cost smart devices

GPS Solutions ◽  
2021 ◽  
Vol 25 (2) ◽  
Author(s):  
Liang Wang ◽  
Zishen Li ◽  
Ningbo Wang ◽  
Zhiyu Wang
Keyword(s):  
Carrier Phase ◽  
Measurement Errors ◽  
Precise Point Positioning ◽  
Low Cost ◽  
Smart Devices ◽  
Dual Frequency ◽  
Static Mode ◽  
Phase Measurements ◽  
Positioning Errors ◽  
Point Positioning

AbstractGlobal Navigation Satellite System raw measurements from Android smart devices make accurate positioning possible with advanced techniques, e.g., precise point positioning (PPP). To achieve the sub-meter-level positioning accuracy with low-cost smart devices, the PPP algorithm developed for geodetic receivers is adapted and an approach named Smart-PPP is proposed in this contribution. In Smart-PPP, the uncombined PPP model is applied for the unified processing of single- and dual-frequency measurements from tracked satellites. The receiver clock terms are parameterized independently for the code and carrier phase measurements of each tracking signal for handling the inconsistency between the code and carrier phases measured by smart devices. The ionospheric pseudo-observations are adopted to provide absolute constraints on the estimation of slant ionospheric delays and to strengthen the uncombined PPP model. A modified stochastic model is employed to weight code and carrier phase measurements by considering the high correlation between the measurement errors and the signal strengths for smart devices. Additionally, an application software based on the Android platform is developed for realizing Smart-PPP in smart devices. The positioning performance of Smart-PPP is validated in both static and kinematic cases. Results show that the positioning errors of Smart-PPP solutions can converge to below 1.0 m within a few minutes in static mode and the converged solutions can achieve an accuracy of about 0.2 m of root mean square (RMS) both for the east, north and up components. For the kinematic test, the RMS values of Smart-PPP positioning errors are 0.65, 0.54 and 1.09 m in the east, north and up components, respectively. Static and kinematic tests both show that the Smart-PPP solutions outperform the internal results provided by the experimental smart devices.

Gas Sensing Properties of TiO2 and SnO2 Nanopowders Obtained through Gel Combustion

2006 ◽  
Vol 45 ◽  
pp. 1828-1833
Author(s):  
Fabio A. Deorsola ◽  
P. Mossino ◽  
Ignazio Amato ◽  
Bruno DeBenedetti ◽  
A. Bonavita ◽  
...  
Keyword(s):  
Response Time ◽  
Metal Oxides ◽  
Gas Sensing ◽  
Low Cost ◽  
High Sensitivity ◽  
Fast Response ◽  
High Specific Surface Area ◽  
Research Field ◽  
Wide Range ◽  
Gel Combustion

Nanostructured semiconductor metal oxides have played a central role in the gas sensing research field, because of their high sensitivity, selectivity and low response time. Among all the processes, developed for the synthesis of nanostructured metal oxides, gel combustion seems to be the most promising route due to low-cost precursors and simplicity of the process. It combines chemical gelation and combustion, involving the formation of a gel from an acqueous solution and an exothermic redox reaction, yielding to very porous and softly agglomerated nanopowders. In this work, nanostructured tin oxide, SnO2, and titanium oxide, TiO2, have been synthesized through gel combustion. Powders showed nanometric particle size and high specific surface area. The so-obtained TiO2 and SnO2 nanopowders have been used as sensitive element of resistive λ sensor and ethanol sensor respectively, realized depositing films of nanopowders dispersed in water onto alumina substrates provided with Pt contacts and heater. TiO2-based sensors showed at high temperature good response, fast response time, linearity in a wide range of O2 concentration and long-term stability. SnO2-based sensors have shown high sensitivity to low concentrations of ethanol at moderate temperature.

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