Low-cost GNSS Receivers Research Articles

On the applicability of low-cost GNSS antennas to precise surveying applications

Abstract This study addresses the scientific question of the applicability of low-cost antennas to the most precise GNSS applications. First of all, we inspect the implications of the availability and quality of low-cost antenna PCC models for precise positioning. From this point of view, we analyze the selected performance indicators of multi-constellation positioning with the representative set of low-cost mass-market GNSS receiver antennas. The processing strategy was based on the relative positioning model, considered the most reliable and precise one. To isolate the antenna-related errors from atmospheric propagation ones, we conducted an experiment based on an ultra-short baseline. As the main indications of low-cost antenna performance, we considered distance and height residuals, defined as the difference between benchmarks and the retrieved from GNSS measurements. We found that the low-cost antenna's PCV effect may significantly affect the final results. On the other hand, the results obtained using certain configurations of low-cost antennas were characterized by only slightly higher standard deviations and discrepancies with respect to benchmark values than those obtained with surveying or geodetic equipment. We identify several sets of low-cost antennas where distance residuals do not exceed 4 mm and height residuals do not exceed 6 mm, which shows the low-cost antenna performance comparable to those achieved using high-grade antennas. On this basis, we conclude that selected low-cost antennas can meet the requirements of high-precision surveying applications.

Evaluating antenna phase center variation effects on tropospheric delay retrieval using a low-cost dual-frequency GNSS receiver

Abstract This study examines the impact of Phase Center Variation (PCV) corrections on Zenith Wet Delay (ZWD) accuracy using a low-cost U-blox ZED-F9P receiver paired with three different antenna configurations: the high-grade TRM57971 antenna, the moderate-grade AS-ANT3BCAL antenna, and the low-cost ANN-MB-00 antenna. Among the three antennas evaluated, the low-cost antenna exhibited the largest PCV magnitude and a pronounced elevation angle dependence. In contrast, the other two antennas demonstrated lower levels of PCV variation. Without PCV corrections, the low-cost antenna showed significant ZWD biases compared to reference values. Applying PCV corrections significantly improved its accuracy, reducing bias and RMS by 88% and 79%, respectively. Moderate- and high-grade antennas experienced minimal improvement with correction. All antennas exhibited remarkable day-to-day repeatability in their residual patterns, despite variations observed in the RMS of phase residuals. This observed repeatability is likely attributable to the presence of unmodeled multipath contributions. The variations in RMS, in turn, can be primarily ascribed to inherent differences in multipath resistance among the antenna designs. This study highlights the critical role of PCV corrections for accurate ZWD estimation with low-cost GNSS receivers. Future research should prioritize the acquisition of manufacturer-provided calibration data for low-cost antennas to streamline and enhance the accuracy of PCV correction applications. Moreover, efforts should be directed toward developing innovative solutions, such as low-cost, multipath-resistant antennas or advanced signal processing algorithms, to mitigate the impact of multipath errors. By addressing these areas, low-cost GNSS solutions can become more reliable and cost-effective tools for tropospheric delay estimation.

Estimation of Surface Water Level in Coal Mining Subsidence Area with GNSS RTK and GNSS-IR

Ground subsidence caused by underground coalmining result in the formation of ponding water on the ground surface. Monitoring the surface water level is crucial for studying the hydrologic cycle in mining areas. In this paper, we propose a combined technique using Global Navigation Satellite System Real-Time Kinematic (GNSS RTK) and GNSS Interferometric Reflectometry (GNSS-IR) to estimate the surface water level in areas of ground subsidence caused by underground coal mining. GNSS RTK is used to measure the geodetic height of the GNSS antenna, which is then converted into the normal height using the local height anomaly model. GNSS-IR is employed to estimate the height from the water surface to the GNSS antenna (or, the reflector height). To enhance the accuracy of the reflector height estimation, a weighted average model has been developed. This model is based on the coefficient of determination of the signal fitted by the Lomb-Scargle spectrogram and can be utilized to combine the reflector height estimations derived from multiple GNSS system and band reflection signals. By subtracting the GNSS-IR reflector height from the GNSS RTK-based normal height, the proposed method-based surface water level estimation can be obtained. In an experimental campaign, a low-cost GNSS receiver was utilized for the collection of dual-frequency observations over a period of 60 days. The collected GNSS observations were used to test the method presented in this paper. The experimental campaign demonstrates a good agreement between the surface water level estimations derived from the method presented in this paper and the reference observations.

Development of Cost-Effective GPS Receiver for Ionospheric Scintillation Monitoring Aided with IoT System

One of the applications of GPS receiver is to detect and measure the irregularities in satellites communication. Many of the studies conducted the research to analyses the transmission data through ionosphere layers. One of the subjects of the research is scintillation. One of the ionosphere scintillation parameters used for measuring the irregularities is amplitude scintillation (S4). However, the survey-grade or GISTM receiver, which is expensive, was commonly used to monitor the parameter. The other alternative is to used common geodetic GPS receiver that capable of collecting the parameters. This study used ZED-F9P with ANN-MB antenna and Raspberry Pi as the prototype to operate. The data collected during the autumnal equinox showed a pattern of strong ionospheric scintillation effects in the post-midnight hours. The study demonstrates the feasibility of using low-cost GNSS receivers for ionospheric monitoring, which has important implications for various applications such as navigation, communication, and space weather monitoring.

The effect of ambiguity resolution on the precision of the GPS/Galileo PPP using a u-blox ZED-F9P low-cost GNSS receiver

Thanks to the increasing number of low-cost dual-frequency GNSS receivers available on the market, the usability of these receivers for geodetic applications is increasing. Recently, PRIDE Lab at GNSS Research Center of Wuhan University has started to produce GNSS observable-specific phase biases for all-frequency. This enables precise point positioning with ambiguity resolution (PPP-AR) not only for conventional frequencies but also for other arbitrary frequencies. In this work, static and kinematic PPP-AR precision of the u-blox ZED-F9P low-cost GNSS receiver are investigated by comparing it with a geodetic-grade GNSS receiver using GPS-only, Galileo-only, and GPS + Galileo combinations for nearly two months period. Wide-lane (WL) and Narrow-lane (NL) AR fixing rates, cycle slips, code multipath, and frequency availability are also investigated for both receivers. In the positioning domain, GPS-only, Galileo-only, and GPS + Galileo PPP positioning precision using float ambiguities is significantly improved after AR for both receivers. GPS + Galileo PPP provides the best precision comparing with the other PPP solutions for both receivers using float and fix ambiguities. For static GPS + Galileo PPP-AR, the standard deviation of north, east, and up components are computed as 2.7/1.7/3.2 mm and 2.2/2.3/5.4 mm for the geodetic receiver and the u-blox receiver, respectively. The results also reveal that kinematic PPP-AR for the u-blox receiver is not as reliable as the geodetic-grade receiver yet suggesting potential for improvement in future iterations.

Low-cost dual-antenna GNSS-based heading and pitch angles estimation considering baseline length constraint

This contribution presents a vehicular heading and pitch angles estimation method based on the dual-antenna GNSS scheme, the baseline length is investigated as a priori nonlinear constraint to improve the estimation accuracy. The coordinates of the formed moving baseline are estimated first, the baseline length is exploited to enhance the ambiguity resolution process, and then its corresponding attitude angles are determined. The capability and reliability of the proposed algorithm are assessed by a real car-borne experiment with off-the-shelf, low-cost GNSS receivers. The driving trajectory contains both stationary periods and dynamic situations under the open sky and dense community environments. The experimental results show that, compared to the classical method that does not consider the baseline length constraint, the accuracy improvements of the proposed method on attitude angles range from 16.7% to 84.0% in different observation conditions, and the attitude errors of ambiguity fixed solutions are dominantly less than 5°.

Multi-frequency smartphone positioning performance evaluation: insights into A-GNSS PPP-B2b services and beyond

In August 2023, Xiaomi unveiled the Redmi K60 Ultra, the first multi-frequency smartphone integrated with BeiDou-3 Navigation Satellite System Precise Point Positioning (PPP-B2b) services and employing PPP technology as the primary positioning method. The positioning enhancement service is provided by the Assisted Global Navigation Satellite System (A-GNSS) location platform developed by the China Academy of Information and Communications Technology. The signaling interaction between the server and the users strictly adheres to the Third Generation of Mobile Communications Technology Partnership Project Long-Term Evolution Positioning Protocol and the Open Mobile Alliance Secure User Plane Location framework. To comprehensively evaluate the Redmi K60 Ultra’s capabilities, this study designed six distinct experimental scenarios and conducted comprehensive research on multi-frequency and multi-GNSS observation noise, Time to First Fix (TTFF), as well as the performance of both GNSS-based and network-based positioning. Experimental results indicate that the GNSS chipset within the Redmi K60 Ultra has achieved a leading position in the consumer market concerning supported satellite constellations, frequencies, and observation accuracy, and is comparable to some low-cost GNSS receivers. A-GNSS positioning can reduce the TTFF from 30 to under 5 s, representing an improvement of over 85% in the cold start speed compared to a standalone GNSS mode. The positioning results show that the A-GNSS PPP-B2b service can achieve positioning performance with RMS errors of less than 1.5 m, 2.5 m, and 4 m in open-sky, realistic, and challenging urban environments. Compared to GNSS-based positioning, cellular network-based Observed Time Difference of Arrival (OTDOA) positioning achieves an accuracy ranging from tens to hundreds of meters in various experimental scenarios and currently functions primarily as coarse location determination. Additionally, this study explores the potential of the Three-Dimensional Mapping-Aided (3DMA) GNSS algorithm in detecting Non-Line-of-Sight signals and enhancing positioning performance. The results indicate that 3DMA PPP, as compared to conventional PPP, can significantly accelerate PPP convergence and improve positioning accuracy by over 30%. Consequently, 3D city models can be utilized as future assistance data for the A-GNSS location platform.

Performance of a Low-Cost GNSS Receiver Using MADOCA Corrections with Precise Point Positioning (PPP) Mode in Thailand

Performance of a Low-Cost GNSS Receiver Using MADOCA Corrections with Precise Point Positioning (PPP) Mode in Thailand

GNSS-Based Narrow-Angle UV Camera Targeting: Case Study of a Low-Cost MAD Robot.

One of the key challenges in Multi-Spectral Automatic Diagnostic (MAD) robot design is the precise targeting of narrow-angle cameras on a specific part of the equipment. The paper shows that a low-cost MAD robot, whose navigation system is based on open-source ArduRover firmware and a pair of low-cost Ublox F9P GNSS receivers, can inspect the 8 × 4 degree ultraviolet camera bounding the targeting error within 0.5 degrees. To achieve this result, we propose a new targeting procedure that can be implemented without any modifications in ArduRover firmware and outperforms more expensive solutions based on LiDAR SLAM and UWB. This paper will be interesting to the developers of robotic systems for power equipment inspection because it proposes a simple and effective solution for MAD robots' camera targeting and provides the first quantitative analysis of the GNSS reception conditions during power equipment inspection. This analysis is based on the experimental results collected during the inspection of the overhead power transmission lines and equipment inspections on the open switchgear of different power plants. Moreover, it includes not only satellite, dilution of precision, and positioning/heading estimation accuracy but also the direct measurements of angular errors that could be achieved on operating power plants using GNSS-only camera targeting.

Evaluation of the single-frequency variometric approach based on low-cost GNSS observations and different satellite combinations for detecting short-term dynamic behaviors

This study presents the capability of the single-frequency (SF) variometric approach (VA) technique with low-cost GNSS observations to detect short-term dynamic behaviors. Harmonic oscillations with amplitudes between 5 and 20 mm and frequencies between 0.3 and 5.0 Hz were generated employing a single-axis shake table to investigate the performance of the SF-VA technique in the structural health monitoring (SHM) system. Besides, a Mw 6.9 Kobe, 1995 earthquake simulation was generated using the shake table to analyze the SF-VA performance for the earthquake early warning (EEW) system. A low-cost u-blox ZED-F9P GNSS receiver and ANN-MB-00 patch antenna were used to collect GNSS observations at a 20 Hz sampling rate during the experiments. The observations were processed using the MATLAB-based open-source PPPH-VA software in real-time (RT) mode, considering eight different satellite combinations. The capability of the SF-VA technique to detect horizontal dynamic behaviors in RT mode was investigated in the frequency and time domains, accepting the displacements from the linear variable differential transformer sensor as a reference. The results in the frequency domain demonstrate that the SF-VA technique with low-cost GNSS observations can successfully detect the peak frequency value of short-term harmonic oscillations up to 5 Hz. Moreover, time domain findings emphasize that the short-time dynamic oscillations can be determined with the SF-VA technique with an accuracy ranging from 0.8 to 6.4 mm. Earthquake simulation experiment results demonstrate that the strong ground motions caused by mega earthquakes can be determined at mm-level by the SF-VA method. The results of both experiments show that multi-GNSS observations contribute to the SF-VA technique considerably. Overall, the findings reveal that the SHM and EEW systems can be operated with low-cost GNSS receivers, and the natural frequency of the man-made structures and accurate displacement values of seismic waveforms can be determined in RT with the SF-VA technique.

On the real-time tropospheric delay estimates using low-cost GNSS receivers and antennas

On the real-time tropospheric delay estimates using low-cost GNSS receivers and antennas

THE APPLICABILITY OF LOW-COST MULTI-FREQUENCY MULTI-GNSS RECEIVERS FOR GEODETIC CONTROL SURVEYING

Abstract. In geodetic surveys, survey-grade receivers are conventionally used due to their accuracy. However, expensive survey-grade receivers deter users from performing geodetic surveys utilizing the technology. Considerably, multi-system and multi-frequency low-cost GNSS receivers are available today, which can already provide good positioning accuracy output. This paper evaluates the performance of low-cost GNSS receivers in single-point positioning, relative positioning, and network solutions compared to survey-grade GNSS receivers. The study used a survey-grade antenna to test the u-blox C099-F9P evaluation kit equipped with the ZED-F9P module, a low-cost GNSS receiver. Simultaneously, the survey-grade GNSS receiver utilizes the same antenna using a GPS splitter to ensure simultaneous observation. Based on the results, the low-cost GNSS receiver is comparable to the survey-grade GNSS receiver for single and relative positioning. For single-point positioning, the low-cost GNSS receiver achieved 1- and 1.5-meter accuracy in horizontal and vertical components at a 95% confidence level, respectively. In relative positioning, it achieved an accuracy of 1 millimeter on average at a 95% confidence level. The network solution utilizes four (4) Active Geodetic Stations of the National Mapping and Resource Information Authority within the National Capital Region, used as reference stations. The low-cost GNSS receiver achieved an average accuracy of 8 millimeters. In summary, the ublox C099-F9P low-cost GNSS receiver achieved better than 1:100,000 or first-order survey accuracy stipulated in DAO 2007-29 surveying standards. Results show that the u-blox C099-F9P is possible for geodetic and other land surveying applications, even for high-accuracy requirements surveys.

Assessment of the Real-Time and Rapid Precise Point Positioning Performance Using Geodetic and Low-Cost GNSS Receivers

Assessment of the Real-Time and Rapid Precise Point Positioning Performance Using Geodetic and Low-Cost GNSS Receivers

Demonstrating the Potential of Low-Cost GNSS Receiver for tidal monitoring, storms, and flood detecting: example of 2022 Noru Storm in Thua Thien Hue province, Vietnam

Extreme hydrological events such as tsunamis, high tides, or storm surges seriously threaten coastal communities. These events result in flooding, property damage, loss of life, and long-term economic and social impacts. Therefore, monitoring and detecting extreme hydrological events significantly affect coastal areas in disaster response efforts. However, the cost of installing and maintaining these stations can be a significant challenge for developing countries. The objective of this study is to use a low-cost GNSS receiver to monitor tides and detect extreme coastal hydrological phenomena by analyzing changes in water level, using analysis of the signal-to-noise ratio (SNR) data. Data used in this study were collected from a GNSS station located in the Tam Giang Lagoon area, Thua Thien Hue, Vietnam, from September to October 2022. The water level based on GNSS-R is compared with the sensor's measured water level, with the Pearson correlation coefficient reaching 0.96 and RMSE of 0.08m. Continuous Wavelet Transform analysis demonstrated the relationship between water levels and extreme hydrological events. The results show that distinct signatures in the data correspond to the Noru typhoon from September 27-29, 2022, and the inundation from October 14-19, 2022, in Thua Thien Hue. This information is the basis for forecasting and early warning of extreme events and informing disaster response and management efforts.

Intercomparison of multi-GNSS signals characteristics acquired by a low-cost receiver connected to various low-cost antennas

With the increasing number of low-cost GNSS antennas available on the market, there is a lack of comprehensive analysis and intercomparison of their performance. Moreover, multi-GNSS observation noises are not well recognized for low-cost receivers. This study characterizes the quality of GNSS signals acquired by low-cost GNSS receivers equipped with eight types of antennas in terms of signal acquisition, multipath error and receiver noise. The differences between various types of low-cost antennas are non-negligible, with helical antennas underperforming in every respect. Compared with a geodetic-grade station, GPS and Galileo signals acquired by low-cost receivers are typically weaker by 3–9 dB-Hz. While the L1, E1 and E5b signals are well-tracked, only 72% and 86% of L2 signals are acquired for GPS and GLONASS, respectively. The signal noise for pseudoranges varies from 0.12 m for Galileo E5b to over 0.30 m for GLONASS L1 and L2, whereas for carrier-phase observations it oscillates around 1 mm for both GPS and Galileo frequencies, but exceeds 3 mm for both GLONASS frequencies. Antenna phase center offsets (PCOs) vary significantly between frequencies and constellations, and do not agree between two antennas of the same type by up to 25 mm in the vertical component. After a field calibration a of low-cost antenna and consistent application of PCOs, the horizontal and vertical accuracy is improved to a few millimeter and a few centimeter level for the multi-GNSS processing with double-differenced and undifferenced approach, respectively. Last but not least, we demonstrate that PPP-AR is possible also with low-cost GNSS receivers and antennas, and improves the precision and convergence time. The results prove that selection of low-cost antenna for a low-cost GNSS receiver is of great importance in precise positioning applications.

Statistical Comparison of Geodetic Baseline for Topographic–Geodetic Purposes Using a Low-Cost GNSS Receiver and Electromagnetic Distance Measurement

Statistical Comparison of Geodetic Baseline for Topographic–Geodetic Purposes Using a Low-Cost GNSS Receiver and Electromagnetic Distance Measurement

Shipborne ZTD Retrieval With a Low-Cost GNSS Receiver

Shipborne ZTD Retrieval With a Low-Cost GNSS Receiver

Performance Evaluation of Low-Cost Dual-Frequency GNSS Receivers for Precise Positioning in Senegal: Issues and Challenges

Performance Evaluation of Low-Cost Dual-Frequency GNSS Receivers for Precise Positioning in Senegal: Issues and Challenges

Assessment of the performance of the TOPGNSS and ANN-MB antennas for ionospheric measurements using low-cost u-blox GNSS receivers

Low-cost GNSS receivers have recently been gaining reliability as good candidates for ionospheric studies. In line with these gains are genuine concerns about improving the performance of these receivers. In this work, we present a comprehensive investigation of the performances of two antennas (the u-blox ANN-MB and the TOPGNSS TOP-106) used on a low-cost GNSS receiver known as the u-blox ZED-F9P. The two antennas were installed on two identical and co-located u-blox receivers. Data used from both receivers cover the period from January to June 2022. Results from the study indicate that the signal strengths are dominantly greater for the receiver with the TOPGNSS antenna than for the receiver with the ANN-MB antenna, implying that the TOPGNSS antenna is better than the ANN-MB antenna in terms of providing greater signal strengths. Summarily, the TOPGNSS antenna also performed better in minimizing the occurrence of cycle slips on phase TEC measurements. There are no conspicuous differences between the variances (computed as 5-min standard deviations) of phase TEC measurements for the two antennas, except for a period around May–June when the TOPGNSS gave a better performance in terms of minimizing the variances in phase TEC. Remarkably, the ANN-MB antenna gave a better performance than the TOPGNSS antenna in terms of minimizing the variances in pseudorange TEC for some satellite observations. For precise horizontal (North and East) positioning, the receiver with the TOPGNSS antenna gave better results, while the receiver with the ANN-MB antenna gave better vertical (Up) positioning. The errors for the receivers of both antennas are typically within about 5 m (the monthly mean was usually smaller than 1 m) in the horizontal direction and within about 10 m (the monthly mean was usually smaller than 4 m) in the vertical direction.

A ROBUST AUTONOMOUS VEHICULAR NAVIGATION SYSTEM USING RIMU-BASED INS/GNSS INTEGRATED SCHEME

Abstract. The application of the INS/GNSS integrated system is widespread in vehicle navigation. However, in certain complex urban areas, achieving accurate positioning for autonomous vehicles at level 3 and beyond presents a challenge. Moreover, ensuring the continuous availability of the navigation system is crucial for maintaining vehicle safety under all circumstances. Consequently, the specifications of the Inertial Measurement Unit (IMU), which have a direct correlation with cost, dominate the performance of the navigation system in environments where GNSS signals are denied or challenging. To implement level 3 autonomous vehicles, a strategy based on redundant IMUs (RIMU) is employed to not only enhance accuracy and availability but reduce the overall cost of the navigation system. This research mainly focuses on the development of a robust autonomous vehicular navigation system by designing an integrated algorithm for the low-cost RIMU and GNSS receiver within the INS/GNSS integration scheme. The positioning performance is analyzed by using a reference system and a benchmark system in the open sky, GNSS challenging, and GNSS outage scenarios.