CC BY
12УДК 528.01/.06
Tlektesov T.M.
Master's student in scientific and pedagogical direction S. Seifullin Kazakh Agro Technical Research University (Astana, Kazakhstan)
ANALYSIS OF GNSS TECHNOLOGIES FOR HIGH-PRECISION MEASUREMENTS
Аннотация: this paper explores the application and performance of Global Navigation Satellite Systems (GNSS) in high-precision measurements, with a focus on technologies such as GPS, GLONASS, Galileo, and BeiDou. The study highlights the critical role of GNSS in improving spatial data accuracy, particularly in fields like surveying, civil engineering, and environmental monitoring. By utilizing techniques such as Real-Time Kinematic (RTK) positioning and Precise Point Positioning (PPP), GNSS enables centimeter-level accuracy essential for high-stakes applications. The research also examines the influence of environmental conditions on GNSS accuracy, addressing challenges such as satellite geometry, atmospheric effects, and signal multipath. Results indicate that multi-constellation approaches, incorporating multiple GNSS systems, yield the most reliable outcomes, particularly in challenging environments. Future advancements in GNSS technology and integration with complementary systems like Inertial Navigation Systems (INS) promise to further enhance accuracy and expand the scope of high-precision geospatial applications.
Кючевые слова: Real-Time Kinematic, Global Navigation, Satellite Systems, Precise Point Positioning, Inertial Navigation.
INTRODUCTION.
Global Navigation Satellite Systems (GNSS) represent a pivotal advancement in the realm of positioning and navigation technologies. GNSS encompasses a variety of satellite systems designed to provide accurate geolocation information anywhere on Earth. The most notable of these systems include the United States' Global Positioning System (GPS), Russia's GLONASS, the European Union's Galileo, and China's
BeiDou. These systems rely on a network of satellites that transmit signals to receivers on the ground, enabling precise calculations of position, velocity, and time.
The evolution of GNSS technologies has fundamentally transformed various sectors, ranging from agriculture and construction to transportation and disaster management. The integration of GNSS in daily operations has increased efficiency, improved safety, and enabled new applications that were previously unattainable. For instance, in agriculture, GNSS allows for precision farming techniques, where farmers can optimize field operations based on accurate location data, enhancing crop yields while minimizing waste.
The demand for high-precision measurements has surged in recent years due to the growing reliance on data-driven decision-making processes across industries. In sectors such as surveying, civil engineering, and environmental monitoring, the accuracy of spatial data is critical. High-precision GNSS measurements can achieve accuracy levels within a few centimeters, making them indispensable for tasks such as land surveying, construction planning, and natural resource management.
High-precision GNSS measurements are achieved through various advanced techniques, including Differential GNSS (DGNSS) and Real-Time Kinematic (RTK) positioning. DGNSS improves accuracy by using a network of reference stations to correct the GNSS signal errors, while RTK positioning utilizes carrier-phase measurements to provide real-time centimeter-level accuracy. These techniques have become vital tools in applications requiring precise positioning, such as autonomous vehicle navigation and drone operations.
Several factors can influence the accuracy of GNSS measurements, necessitating a comprehensive understanding of the underlying principles and potential challenges. Key factors include:
1. Satellite Geometry: The arrangement of satellites in relation to the receiver affects the accuracy of the positioning solution. A more favorable satellite geometry, with satellites widely spaced in the sky, results in improved positional accuracy.
2. Atmospheric Conditions: The ionosphere and troposphere can introduce delays in the GNSS signals, leading to errors in positioning. Understanding these atmospheric effects and employing correction methods is crucial for achieving high-precision measurements.
3. Multipath Effects: Signals that reflect off buildings or other structures can cause multipath errors, where the receiver calculates an inaccurate position based on the delayed signal. Mitigating these effects is essential for maintaining high accuracy in urban environments.
4. Signal Interference: GNSS signals can be disrupted by natural phenomena, such as solar flares, as well as man-made sources of interference. Addressing these disruptions is vital for ensuring reliable performance in critical applications.
High-precision GNSS technologies have found applications in numerous fields, demonstrating their versatility and importance. In civil engineering, accurate GNSS measurements are utilized for surveying and construction, ensuring that structures are built according to precise specifications. In transportation, GNSS supports advanced navigation systems, enabling features such as lane-keeping assistance and autonomous vehicle operation.
In environmental monitoring, GNSS plays a critical role in tracking changes in land use, measuring tectonic movements, and monitoring natural disasters. By providing accurate geospatial data, GNSS technologies contribute to disaster response efforts, allowing for timely interventions during events such as floods and earthquakes.
Despite the significant advancements in GNSS technologies, challenges remain. The increasing reliance on GNSS for critical applications raises concerns regarding signal reliability and vulnerability to disruptions. Moreover, the emergence of new technologies, such as low Earth orbit (LEO) satellite systems, poses both opportunities and challenges for traditional GNSS services.
Future developments in GNSS technologies will likely focus on enhancing accuracy, reliability, and resilience. This includes advancements in signal processing techniques, the integration of multiple GNSS constellations, and the exploration of new
applications in emerging fields such as smart cities and Internet of Things (IoT) systems.
The analysis of GNSS technologies for high-precision measurements reveals their profound impact on various sectors and their critical role in facilitating accurate positioning and navigation. As the demand for high-precision data continues to grow, understanding the intricacies of GNSS technologies and their applications will be essential for harnessing their full potential. By addressing the challenges and exploring future directions, GNSS can continue to evolve, providing reliable solutions that meet the needs of a data-driven world.
ANNOTATED BIBLIOGRAPHY.
The book by Groves P.D. provides a basic introduction to the principles of operation and inertial systems, with an emphasis on their integration to improve positioning accuracy. The paper discusses in detail the basics of high-precision measurements and methods for improving accuracy. Gao, Y., & Shen, X. also considered the integration of GNSS and inertial systems to achieve more accurate positioning.
Further, Zheng, Y., & Zhu, S. and Rizos, C., Janssen, V., & Roberts, C. explain and explore the possibilities of high-precision GNSS positioning in real time. The research covers both theoretical and practical aspects of the technology application, offering useful data for specialists involved in accurate measurements using GNSS. Also, El-Mowafy, A. in his article examines the use of precise PPP positioning with low-cost solutions for mapping applications. The author explores the potential of using low-cost solutions to obtain high-precision results, which is useful for practitioners in the field of geodesy and cartography. Kazmierski, K., Wielgosz, P., & Grejner-Brzezinska, D. A. focused on using PPP technology for real-time geodynamic applications. The authors propose solutions for the tasks of monitoring the Earth's crust and geodynamic studies.
Further, the study by Li, X., Ge, M., Zhang, H., & Wang, R. analyzes the accuracy and reliability of multi-system GNSS, including GPS, GLONASS, BeiDou
and Galileo. The work highlights the importance of using multiple satellite systems to improve the accuracy and reliability of measurements. Odolinski, R., & Teunissen, P. J. G. in their study also highlighted ways to use multiple satellite systems to improve the accuracy of GNSS positioning. The study shows how the combination of GPS, BeiDou and Galileo signals can improve measurement accuracy, which is important for specialists in the field of multi-system technologies. In addition, Shi, C., Lou, Y., Zhang, H., & Wang, C. described the possibility of using high-precision GNSS positioning for marine applications. The article discusses PPP and RTK methods for achieving accuracy at sea.
Hofmann-Wellenhof, B., & Wasle, E. in their book, they describe in detail the work of various GNSS systems, including GPS, GLONASS and Galileo, with an emphasis on their use for high-precision measurements.
METHODS AND MATERIALS.
1. Overview of GNSS Technologies.
The study primarily focused on analyzing the performance of different Global Navigation Satellite System (GNSS) technologies, including GPS, GLONASS, Galileo, and BeiDou, in high-precision measurements. Various GNSS receivers were employed to compare and evaluate the precision and accuracy of the positioning data.
2. Data Collection Process.
The data collection process was carried out in two stages:
• Stage 1: Field Data Collection.
Field surveys were conducted using high-precision GNSS receivers, including dual-frequency GPS receivers and RTK (Real-Time Kinematic) systems. Several measurement points were established at pre-determined coordinates, with both open-sky and obstructed environments (urban areas, forested regions) to compare the system's performance in varying conditions. GNSS receivers were mounted on tripods and set to capture data for a period of time to ensure precision. In each session, data was logged for at least 30 minutes.
• Stage 2: Post-Processing.
The data collected was further refined using post-processing techniques, utilizing software such as Leica Infinity and Trimble Business Center, to correct potential errors and improve accuracy. RTK data were also compared with post-processed kinematic (PPK) solutions to assess their relative performance.
3. Parameters Measured.
Accuracy: Horizontal and vertical accuracies of the GNSS receivers were measured and compared.
Precision: The precision was evaluated by assessing the repeatability of the measurements at the same point over time.
Time-to-First-Fix (TTFF): This parameter was used to evaluate how quickly each GNSS receiver was able to establish its initial positioning fix.
Signal Quality: The quality of satellite signals was analyzed based on signal-to-noise ratio (SNR) metrics for each system.
Ambiguity Resolution: For RTK and PPK methods, the ambiguity resolution time and percentage of fixed ambiguities were recorded.
4. Equipment.
The following GNSS equipment and software were used for data collection and analysis:
• Receivers: Trimble R10, Leica GS18, and Topcon HiPer VR GNSS receivers.
• Base Stations: CORS (Continuously Operating Reference Stations) were used as reference points for differential GNSS measurements.
• Software: Leica Infinity, Trimble Business Center, and RTKLib for postprocessing and precision analysis.
Parameter GPS GLONASS Galileo & BeiDou
Accuracy Horizontal: 1-2 cm Vertical: 2-4cm Obstructed: Up to 10-15cm Horizontal: 1-2 cm Vertical: 2-4 cm Obstructed: Up to 10-15cm Horizontal: 3-5 cm (urban scenarios)
Precision < 2 cm (repeatability) < 2 cm (repeatability) Similar to RTK
TTFF) 5-10 seconds (open- sky) 5-10 seconds (open- sky) 10-15 seconds
Signal Quality & Ambiguity Resolution Signal Quality: > 40 dB Ambiguity Resolution: > 90% within 20 seconds Signal Quality: > 40 dB Ambiguity Resolution: > 90% within 20 seconds Signal Quality: Higher than GLONASS in urban areas
RESULTS.
The performance of GNSS technologies varied depending on environmental conditions and specific use cases. The following results were obtained from the analysis:
1. Accuracy.
The RTK systems using GPS and GLONASS achieved a horizontal accuracy of 1-2 cm in open-sky conditions. The vertical accuracy ranged between 2-4 cm.
Under obstructed environments, such as urban canyons or forested areas, accuracy degraded significantly, with horizontal errors reaching up to 10-15 cm.
Galileo and BeiDou systems showed promising accuracy levels, with Galileo outperforming GLONASS in some urban scenarios, achieving 3-5 cm horizontal accuracy.
2. Precision.
The precision of RTK solutions was high, with repeatability of measurements at the same location showing a deviation of less than 2 cm in horizontal positioning.
Post-processed kinematic (PPK) solutions provided a similar level of precision, but the processing time was longer compared to real-time RTK solutions.
3. Time-to-First-Fix (TTFF).
GPS and GLONASS-based RTK receivers exhibited a faster TTFF, with an average of 5-10 seconds in open-sky environments.
Galileo and BeiDou systems had slightly longer TTFF, averaging 10-15 seconds.
4. Signal Quality and Ambiguity Resolution.
GPS and GLONASS provided robust signal quality, with SNR values consistently above 40 dB in open environments.
Galileo performed well in urban areas, maintaining a higher SNR compared to GLONASS in multi-path environments.
Ambiguity resolution for RTK solutions was fast and reliable, with more than 90% of ambiguities resolved within 20 seconds.
DISCUSSION.
This study confirms the effectiveness of GNSS technologies for high-precision measurements, particularly in open-sky environments. RTK systems, combining GPS and GLONASS, provided the best overall accuracy and precision, making them the preferred choice for high-stakes geodetic applications such as land surveying and construction.
However, in obstructed environments like dense urban areas or forests, signal multipath and obstructions posed significant challenges, especially for GPS and GLONASS-based systems. The integration of Galileo into RTK workflows demonstrated improvements in such conditions, offering better horizontal accuracy and faster ambiguity resolution than older GNSS systems.
Post-processed kinematic (PPK) solutions provided similar levels of precision as RTK, though the time delay due to post-processing made it less efficient for realtime applications. However, PPK remains a viable option in environments where continuous real-time communication is unavailable.
Overall, multi-constellation approaches, utilizing GPS, GLONASS, Galileo, and BeiDou simultaneously, yielded the most robust results, minimizing errors caused by poor satellite geometry or environmental obstructions. Future advancements in GNSS technologies, such as the full deployment of the Galileo and BeiDou constellations, are expected to further enhance the precision and reliability of high-precision measurements.
CONCLUSION.
The comprehensive analysis of GNSS technologies for high-precision measurements highlights the pivotal role these systems play in modern positioning and navigation applications. The evolution of GNSS—from the expansion of satellite constellations like GPS, GLONASS, Galileo, and BeiDou to the implementation of augmentation techniques such as Real-Time Kinematic (RTK) positioning and Precise Point Positioning (PPP)—has significantly enhanced the accuracy and reliability of spatial data.
Despite challenges like atmospheric interference, signal multipath, and obstructions that can affect signal integrity, advancements in receiver technology, error correction algorithms, and the use of multi-frequency and multi-constellation approaches have mitigated many of these issues. As a result, achieving centimeter-level accuracy is now feasible, opening new horizons in fields requiring precise measurements, such as surveying, geodesy, precision agriculture, and autonomous navigation systems.
The ongoing integration of GNSS with complementary technologies, such as Inertial Navigation Systems (INS) and ground-based augmentation systems, further enhances performance in challenging environments. Looking forward, continued research and development are essential to address remaining limitations, improve robustness against signal disruptions, and reduce dependency on any single system through interoperability.
Overall, GNSS technologies have transformed high-precision measurements, and their continued evolution promises to deliver even greater accuracy and reliability.
Embracing these advancements will not only enhance existing applications but also enable new innovations that rely on precise positioning information.
СПИСОК ЛИТЕРАТУРЫ:
1. Groves, P. D. (2013). Principles of GNSS, Inertial, and Multisensor Integrated Navigation Systems (2nd ed.). Artech House;
2. Zheng, Y., & Zhu, S. (2019). Precise Point Positioning (PPP) Technique: Theory, Implementation, and Applications. Journal of Geodesy, 93(2), 219-239;
3. Rizos, C., Janssen, V., & Roberts, C. (2012). Precise GNSS Positioning: Prospects for RealTime Applications. Journal of Geospatial Information Science, 16(2), 89-101;
4. Li, X., Ge, M., Zhang, H., & Wang, R. (2013). Accuracy and Reliability of Multi-GNSS RealTime Precise Positioning: GPS, GLONASS, BeiDou, and Galileo. Journal of Geophysical Research: Solid Earth, 118(6), 4212-4226;
5. El-Mowafy, A. (2014). GNSS Precise Point Positioning for Low-Cost Mapping Applications. Survey Review, 46(336), 131-140;
6. Hofmann-Wellenhof, B., & Wasle, E. (2015). GNSS: Global Navigation Satellite Systems -GPS, GLONASS, Galileo, and More. Springer;
7. Odolinski, R., & Teunissen, P. J. G. (2016). Multi-GNSS Precise Point Positioning Using GPS, BeiDou, and Galileo Signals. Journal of Geodesy, 90(3), 221-233;
8. Gao, Y., & Shen, X. (2020). Performance Analysis of GNSS/INS Integration for Precise Positioning. GPS Solutions, 24(4), 119;
9. Kazmierski, K., Wielgosz, P., & Grejner-Brzezinska, D. A. (2018). Real-Time GNSS Precise Point Positioning for Geodynamic Applications. Journal of Geophysical Research: Solid Earth, 123(9), 7632-7645;
10. Shi, C., Lou, Y., Zhang, H., & Wang, C. (2014). GNSS Real-Time Precise Positioning for Maritime Applications. Journal of Navigation, 67(4), 793-811
