Recent advances and perspectives in GNSS PPP-RTK

Hou, Pengyu; Zha, Jiuping; Li, Teng; Zhang, Baocheng

doi:10.1088/1361-6501/acb78c

Cited by 17 publications

(5 citation statements)

References 139 publications

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“…This grid has a square configuration, each side measuring 60 m in length, with a 4 m interval between control points. The coordinates for each control point were determined using Real-Time Kinematic (RTK) positioning [28], achieving an elevation accuracy of up to 0.05 m. The control point grid collection approach for all 13 laser footprints was consistent with the pattern shown in Figure 2b for footprint 305904555.671. Figure 2c depicts the collection of control point data using RTK.…”

Section: Gf-7 Laser Altimeter Pointing Calibration Area and Datamentioning

confidence: 96%

Fine Calibration Method for Laser Altimeter Pointing and Ranging Based on Dense Control Points

Xu,

Mo,

Wang

et al. 2024

Remote Sensing

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Satellite laser altimetry technology, a novel space remote sensing technique, actively acquires high-precision elevation information about the Earth’s surface. However, the accuracy of laser altimetry can be compromised by alterations in the satellite-ground environment, thermal dynamics, and cosmic radiation. These factors may induce subtle variations in the installation and internal structure of the spaceborne laser altimeter on the satellite platform, diminishing measurement precision. In-orbit calibration is thus essential to enhancing the precision of laser altimetry. Through collaborative calculations between satellite and ground stations, we can derive correction parameters for laser pointing and ranging, substantially improving the accuracy of satellite laser altimetry. This paper introduces a sophisticated calibration method for laser altimeter pointing and ranging that utilizes dense control points. The approach interpolates discrete ground control point data into continuous simulated terrain using empirical Bayesian kriging, subsequently categorizing the data for either pointing or ranging calibration according to their respective functions. Following this, a series of calibration experiments are conducted, prioritizing “pointing” followed by “ranging” and continuing until the variation in the ranging calibration results falls below a predefined threshold. We employed experimental data from ground control points (GCPs) in Xinjiang and Inner Mongolia, China, to calibrate the GaoFen-7 (GF-7) satellite Beam 2 laser altimeter as per the outlined method. The calibration outcomes were then benchmarked against those gleaned from infrared laser detector calibration, revealing disparities of 1.12 s in the pointing angle and 2 cm in the ranging correction value. Post validation with ground control points, the measurement accuracy was refined to 0.15 m. The experiments confirm that the proposed calibration method offers accuracy comparable to that of infrared laser detector calibration and can facilitate the updating of 1:10,000 topographic maps utilizing stereo optical imagery. Furthermore, this method is more cost-effective and demands fewer personnel for ground control point collection, enhancing resource efficiency compared to traditional infrared laser detector calibration. The proposed approach surpasses terrain-matching limitations when calibrating laser ranging parameters and presents a viable solution for achieving frequent and high-precision in-orbit calibration of laser altimetry satellites.

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Section: Gf-7 Laser Altimeter Pointing Calibration Area and Datamentioning

confidence: 96%

Fine Calibration Method for Laser Altimeter Pointing and Ranging Based on Dense Control Points

Xu,

Mo,

Wang

et al. 2024

Remote Sensing

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“…The single-difference clock difference and ambiguity will absorb the pseudorange and carrier phase hardware delay, which allows us to further simplify equation (3) as follows [17]:…”

Section: Gnss-rtsd Time Synchronizationmentioning

confidence: 99%

Evaluation of receiver calibration based on clock-steering for time–frequency transfer

Guo,

Chen,

Gong

et al. 2023

Meas. Sci. Technol.

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Calibrating the Global Navigation Satellite System (GNSS) time-frequency transfer system is crucial for accurate GNSS time-frequency transfer. The most commonly used relative calibration method relies on the common-clock to eliminate clock differences. However, it cannot eliminate the changes in clock signal reference point delay (REFDLY). The changes in REFDLY during calibration could not be ignored, especially for ordinary users in an unstable environment. To address this issue, we use the GNSS real-time single-difference (GNSS-RTSD) time synchronization calibration based on clock-steering, which can detect the change in REFDLY. According to this method, the clock differences and REFDLY are eliminated simultaneously. We installed two GNSS antennas on the roof of the Xinghu Building of Wuhan University and designed a clock synchronization terminal to evaluate the performance of this method. The data were collected on Day Of Year (DOY) 152~156, 167~171, 222~226, 231~235, 244, 258, 260, and 262 in 2022. In accordance with the calibration results, the standard deviation better than 100ps, and the stability reaches 10^{-15}@10000s. Also, the time variance better than 60ps, and the uncertainty u_{CAL} better than 0.5 ns. Compared to the common-clock calibration, one of the most significant benefits is the elimination of REFDLY, which leads to decreased uncertainty and better stability over both the short-term and long-term.

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“…or centimeter level, its characteristics are high sample and high accuracy, which has been applied to many fields such as earthquake early warning, landslide monitoring, weather monitoring, etc [1,2]. It has been shown that positioning accuracy and convergence time can be significantly improved by fixing the carrier phase ambiguity in the process of PPP [3].…”

Section: Introductionmentioning

confidence: 99%

PPP-AR reference satellite selection based on the observation quality factors

Li,

Huang,

Wang

et al. 2024

Meas. Sci. Technol.

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In this contribution, we propose a multi-indicators comprehensive evaluation method of the Global Navigation Satellite System (GNSS) based on entropy weight-grey correlation analysis for reference satellite selection of PPP-AR. The comprehensive evaluation includes the observations index selection, the index normalization, the calculation of index entropy weight and the grey correlation analysis. The position dilution of precision (PDOP), carrier-to-noise density ratio (C/N0) and pseudorange multipath indicators are selected to construct a multi-indicator matrix, normalize the above indicators, and then calculate the entropy weight of each evaluation indicator to determine the indicator weights. Meanwhile, after selecting the optimal indicator set, the matrix is constructed to find the grey correlation coefficient and finally the grey correlation degree. According to the above method, the quality ranking of satellite observations for each epoch can be obtained, and the observation value with the highest ranking is used as the reference satellite during the PPP-AR. One-week observations from 243 MGEX stations are selected to conduct GPS-only, Galileo-only and BDS-3-only kinematic PPP-AR, the reference satellite selection method using the highest-elevation and the proposed method is applied, respectively. The results show that, compared with the traditional method, the positioning accuracies, convergence time and ambiguity fixed rates all can be improved using the proposed method. The positioning accuracies of GPS can be improved by about 10.81%, 5.10%, 2.95% and 5.54% in the east(E), north(N), up(U) and three-dimensional(3D) directions, respectively; 7.94%, 5.11%, 5.04% and 6.02% for Galileo; and 14.94%, 5.80%, 3.98% and 8.81% for BDS-3. The average improvements of convergence time in the east, north and up directions are 4.67%, 2% and 4% for GPS, BDS-3 and Galileo, respectively. The ambiguity fixed rates are improved by 7.31%, 6.89% and 1.45% for GPS, BDS-3 and Galileo between the 80%-100% range, respectively.

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Recent advances and perspectives in GNSS PPP-RTK

Cited by 17 publications

References 139 publications

Fine Calibration Method for Laser Altimeter Pointing and Ranging Based on Dense Control Points

Fine Calibration Method for Laser Altimeter Pointing and Ranging Based on Dense Control Points

Evaluation of receiver calibration based on clock-steering for time–frequency transfer

PPP-AR reference satellite selection based on the observation quality factors

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