Algorithms for Sparse Network-based RTK GPS Positioning and Performance Assessment

The average inter-station distances in most established network Real Time Kinematic (RTK) systems are constrained to around 50 km. A sparse network RTK system with an average inter-station distance of up to 300 km would have many appealing advantages over a conventional one, including a significant reduction in the development and maintenance costs. The first part of this paper introduces the key approaches for sparse network RTK positioning technology. These include long-range reference baseline ambiguity resolution and real-time kinematic ambiguity resolution for the rover receivers. The proposed method for long-range kinematic ambiguity resolution can overcome the network weaknesses through three procedures: application of the interpolated corrections from the sparse network only to wide-lane combination; searching the ambiguities of wide-lane combination; and searching L1 ambiguities with wide-lane combination and ionosphere-free observables. To test these techniques, a network including ten reference stations was created from the Ordnance Survey's Network (OS NetTM) that covers the whole territory of the United Kingdom (UK). The average baseline length of this sparse network is about 300 km. To assess the positioning performance, nine rover stations situated inside and outside the network were also selected from the OS Net™. Finally, the accuracy of interpolated corrections, the positioning accuracy and the initialization time required for precise positioning were estimated and analysed. From the observed performance of each rover receiver, and the accuracy of interpolated network corrections, it can be concluded that it is feasible to use a sparse reference station network with an average inter-station distance up to 300 km for achieving similar performance to traditional network RTK positioning. The proposed approach can provide more cost-efficient use of network RTK (NRTK) positioning for engineering and environmental applications that are currently being delivered by traditional network RTK positioning technology.

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Performance Assessment of a Long Range Reference Station Ambiguity Resolution Algorithm for Network RTK GPS Positioning

Survey Review ◽

10.1179/003962610x12572516251600 ◽

2010 ◽

Vol 42 (316) ◽

pp. 132-145 ◽

Cited By ~ 5

Author(s):

Weiming Tang ◽

Xiaolin Meng ◽

Chuang Shi ◽

Jingnan Liu

Keyword(s):

Performance Assessment ◽

Long Range ◽

Ambiguity Resolution ◽

Reference Station ◽

Gps Positioning ◽

Network Rtk ◽

Resolution Algorithm ◽

Rtk Gps

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Accuracy Assessment of the Network Real-Time Kinematic Techniques for Geodetic and Plane Coordinates

ASM Science Journal ◽

10.32802/asmscj.2021.617 ◽

2021 ◽

Vol 16 ◽

pp. 1-15

Author(s):

Ami Hassan Md Din ◽

Nur Adawiyyah Maziyyah Abu Bakar ◽

Nur Adilla Zulkifli ◽

Muhammad Asyran Che Amat ◽

Mohammad Hanif Hamden

Keyword(s):

Real Time ◽

Accuracy Assessment ◽

Reference Station ◽

Baseline Length ◽

Virtual Reference ◽

Accuracy Measurement ◽

Geodetic Coordinates ◽

Real Time Kinematic ◽

Gnss Network ◽

High Accuracy Measurement

Virtual Reference Station (VRS), Master-Auxiliary Corrections (MAX) and Individualised Master-Auxiliary Corrections (IMAX) are among the Network Real-Time Kinematic (NRTK) techniques supported by Malaysia Real-Time Kinematic GNSS Network (MyRTKnet) in rendering network-based solution to users. However, different network corrections have different limitations due to different manufacturers hence offering varieties output. Therefore, this study was conducted to assess the accuracy of VRS, MAX and IMAX for geodetic and plane coordinates. Three (3) techniques were implemented to observe points at Universiti Teknologi Malaysia (UTM) and cadastral lot in Johor Bahru. The results were analysed based on assessment with known values and baseline lengths. The findings showed that the accuracy of all techniques ranged from 0.16 to 3.61 cm (horizontal) and 2.86 to 6.20 cm (vertical) for geodetic coordinates. For plane coordinates, the values varied from 0.3 to 4.22 cm (horizontal) and 2.1 to 8.26 cm (vertical). IMAX provided the worst accuracy compared to others due to incompatibility of Radio Technical Commission for Maritime Services (RTCM) format. Moreover, the accuracy decreases as the baseline length between rover and reference station increases. In conclusion, VRS and MAX yielded acceptable accuracy and can be safely chosen rather than IMAX. Furthermore, the baseline length for applications involving high accuracy measurement should also be considered.

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High-Accuracy Real-Time Kinematic Positioning with Multiple Rover Receivers Sharing Common Clock

Remote Sensing ◽

10.3390/rs13040823 ◽

2021 ◽

Vol 13 (4) ◽

pp. 823

Author(s):

Lin Zhao ◽

Jiachang Jiang ◽

Liang Li ◽

Chun Jia ◽

Jianhua Cheng

Keyword(s):

Real Time ◽

Ambiguity Resolution ◽

Temporal Stability ◽

Estimation Method ◽

Satellite System ◽

Integer Ambiguity ◽

Dual Frequency ◽

Kinematic Positioning ◽

Real Time Kinematic ◽

Satellite Visibility

Since the traditional real-time kinematic positioning method is limited by the reduced satellite visibility from the deprived navigational environments, we, therefore, propose an improved RTK method with multiple rover receivers sharing a common clock. The proposed method can enhance observational redundancy by blending the observations from each rover receiver together so that the model strength will be improved. Integer ambiguity resolution of the proposed method is challenged in the presence of several inter-receiver biases (IRB). The IRB including inter-receiver code bias (IRCB) and inter-receiver phase bias (IRPB) is calibrated by the pre-estimation method because of their temporal stability. Multiple BeiDou Navigation Satellite System (BDS) dual-frequency datasets are collected to test the proposed method. The experimental results have shown that the IRCB and IRPB under the common clock mode are sufficiently stable for the ambiguity resolution. Compared with the traditional method, the ambiguity resolution success rate and positioning accuracy of the proposed method can be improved by 19.5% and 46.4% in the restricted satellite visibility environments.

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Examining the Accuracy of Network RTK and Long Base RTK Methods with Repetitive Measurements

Journal of Sensors ◽

10.1155/2019/3572605 ◽

2019 ◽

Vol 2019 ◽

pp. 1-12 ◽

Cited By ~ 3

Author(s):

Tamer Baybura ◽

İbrahim Tiryakioğlu ◽

Mehmet Ali Uğur ◽

Halil İbrahim Solak ◽

Şeyma Şafak

Keyword(s):

Real Time ◽

Precise Point Positioning ◽

High Accuracy ◽

Base Station ◽

Network Rtk ◽

Real Time Kinematic ◽

Study Results ◽

Point Positioning

Real-time kinematic (RTK) technique is important for mapping applications requiring short measure time, the distance between rover and base station, and high accuracy. There are several RTK methods used today such as the traditional RTK, long base RTK (LBRTK), network RTK (NRTK), and precise point positioning RTK (PPP-RTK). NRTK and LBRTK are popular with the advantage of the distance, the time, and accuracy. In the present study, the NRTK and LBRTK measurements were compared in terms of accuracy and distance in a test network with 6 sites that was established between 5 and 60 km. Repetitive NRTK and LBRTK measurements were performed on 6 different days in 2015-2017-2018 and additionally 4 campaigns of repetitive static measurements were carried out in this test network. The results of NRTK and LBRTK methods were examined and compared with all relevant aspects by considering the results of the static measurements as real coordinates. The study results showed that the LBRTK and NRTK methods yielded similar results at base lengths up to 40 km with the differences less than 3 cm horizontally and 4 cm vertically.

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Real-Time Kinematic Precise Orbit Determination for LEO Satellites Using Zero-Differenced Ambiguity Resolution

Remote Sensing ◽

10.3390/rs11232815 ◽

2019 ◽

Vol 11 (23) ◽

pp. 2815 ◽

Cited By ~ 1

Author(s):

Xingxing Li ◽

Jiaqi Wu ◽

Keke Zhang ◽

Xin Li ◽

Yun Xiong ◽

...

Keyword(s):

Real Time ◽

Ambiguity Resolution ◽

Orbit Determination ◽

Precise Orbit Determination ◽

The Real ◽

Precise Orbit ◽

Ambiguity Fixing ◽

Real Time Kinematic ◽

Leo Satellites ◽

Fixed Solution

The rapid growing number of earth observation missions and commercial low-earth-orbit (LEO) constellation plans have provided a strong motivation to get accurate LEO satellite position and velocity information in real time. This paper is devoted to improve the real-time kinematic LEO orbits through fixing the zero-differenced (ZD) ambiguities of onboard Global Navigation Satellite System (GNSS) phase observations. In the proposed method, the real-time uncalibrated phase delays (UPDs) are estimated epoch-by-epoch via a global-distributed network to support the ZD ambiguity resolution (AR) for LEO satellites. By separating the UPDs, the ambiguities of onboard ZD GPS phase measurements recover their integer nature. Then, wide-lane (WL) and narrow-lane (NL) AR are performed epoch-by-epoch and the real-time ambiguity–fixed orbits are thus obtained. To validate the proposed method, a real-time kinematic precise orbit determination (POD), for both Sentinel-3A and Swarm-A satellites, was carried out with ambiguity–fixed and ambiguity–float solutions, respectively. The ambiguity fixing results indicate that, for both Sentinel-3A and Swarm-A, over 90% ZD ambiguities could be properly fixed with the time to first fix (TTFF) around 25–30 min. For the assessment of LEO orbits, the differences with post-processed reduced dynamic orbits and satellite laser ranging (SLR) residuals are investigated. Compared with the ambiguity–float solution, the 3D orbit difference root mean square (RMS) values reduce from 7.15 to 5.23 cm for Sentinel-3A, and from 5.29 to 4.01 cm for Swarm-A with the help of ZD AR. The SLR residuals also show notable improvements for an ambiguity–fixed solution; the standard deviation values of Sentinel-3A and Swarm-A are 4.01 and 2.78 cm, with improvements of over 20% compared with the ambiguity–float solution. In addition, the phase residuals of ambiguity–fixed solution are 0.5–1.0 mm larger than those of the ambiguity–float solution; the possible reason is that the ambiguity fixing separate integer ambiguities from unmodeled errors used to be absorbed in float ambiguities.

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Carrier Phase GPS Navigation to the North Pole

Journal of Navigation ◽

10.1017/s037346339800808x ◽

1999 ◽

Vol 52 (1) ◽

pp. 80-89 ◽

Cited By ~ 2

Author(s):

T. Moore ◽

G. W. Roberts

Keyword(s):

Ambiguity Resolution ◽

Carrier Phase ◽

Integer Ambiguity Resolution ◽

North Pole ◽

Integer Ambiguity ◽

Reference Station ◽

Baseline Length ◽

Cycle Slips ◽

The North ◽

Long Baseline

Over the last few years, on-the-fly integer ambiguity resolution for GPS has proven to be successful over short baselines (<20 km). However, the remaining challenge has been to extend the length of the baseline between the reference station and the mobile receiver, whilst still maintaining the capability of on-the-fly resolution and true carrier-based kinematic positioning. The goal has been to achieve centimetric level positioning at ranges of over 500 km. New techniques have been developed at the University of Nottingham to allow very long baseline integer ambiguity resolution, on-the-fly. A major problem with the use of carrier phase data is that posed by cycle slips. A technique for detecting and correcting cycle slips has been developed, and its use is discussed in this paper. The new technique has been proven through a series of trials, one of which included two flights to the North Pole, performing centimetric level positioning all the way to the pole. For many years, the GD Aero-Systems Course of the Air Warfare Centre based at RAF Cranwell executed a series of equipment flight trials to the North Pole, called the ARIES Flights. In May 1996, the authors were fortunate to take part in both flights, via Iceland and Greenland, to the North Pole. Based on reference stations at Thule Air Base, integer ambiguity resolution was accomplished, on-the-fly, and centimetric level navigation maintained throughout the flights. Earlier trials detailed in the paper demonstrate that the technique can resolve integer ambiguities on-the-fly within a few seconds over a baseline length of approximately 134 km, resulting in an accuracy of 12 cm. The majority of the residual error source for this being the ionosphere.

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Atmospheric Effects on RTK Network in Florida

Boletim de Ciências Geodésicas ◽

10.1590/s1982-21702015000300048 ◽

2015 ◽

Vol 21 (4) ◽

pp. 814-831 ◽

Cited By ~ 1

Author(s):

M. Berber ◽

N. Arslan

Keyword(s):

Real Time ◽

Atmospheric Effects ◽

Network Rtk ◽

Real Time Kinematic ◽

Almost All ◽

Better Than

Commonly used real time kinematic (RTK) network (RTK Network) techniques, i.e., MAX, I-MAX, FKP and VRS, are tested by taking monthly measurements for a year in Florida. Additionally, RTCM message versions 2 and 3 are used with I-MAX and VRS measurements. The results revealed that mostly, horizontal coordinates vary a few centimeters and generally changes in vertical coordinates are less than two decimeters. In terms of horizontal coordinates, the best results are produced by I-MAX3 method and FKP yielded the worst results. In terms of vertical coordinates, almost all results look alike; however, the best results are produced by VRS3 method. It appears that I-MAX3 performed better than I-MAX2 and VRS3 performed better than VRS2. Yet, MAX did not stand out among other techniques.

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Performance of GPS Precise Time and Frequency Transfer with Integer Ambiguity Resolution

Measurement Science and Technology ◽

10.1088/1361-6501/ac3a30 ◽

2021 ◽

Author(s):

Pengfei Zhang ◽

Rui Tu ◽

Xiaochun Lu ◽

Yuping Gao ◽

Lihong Fan

Keyword(s):

Real Time ◽

Ambiguity Resolution ◽

Integer Ambiguity Resolution ◽

Integer Ambiguity ◽

Convergence Time ◽

Processing Modes ◽

Wide Lane ◽

Frequency Transfer ◽

Fixed Solution ◽

Precise Time

Abstract The global positioning system (GPS) carrier-phase (CP) technique is a widely used spatial tool for remote precise time and frequency transfer. However, the performance of traditional GPS time and frequency transfer has been limeted because the ambiguity paramter is still the float solution. This study focuses on the performance of GPS precise time and frequency transfer with integer ambiguity resolution and discusses the corresponding mathematical model. Fractional-cycle bias (FCB) products were estimated by using an ionosphere-free combination. The results show that the satellite wide-lane (WL) FCB products are stable, with a standard deviation (STD) of 0.006 cycles. The narrow-lane (NL) FCB products were estimated over 15 min with the STD of 0.020 cycles. More than 98% of the WL and NL residuals are smaller than 0.25 cycles, which helps to fix the ambiguity into integers during the time and frequency transfer. Subsequently, the performances of the time transfers with integer ambiguity resolution at two time links between international laboratories were assessed in real-time and post-processing modes and compared. The results show that fixing the ambiguity into an integer in the real-time mode significantly decreases the convergence time compared with the traditional float approach. The improvement is ~49.5%. The frequency stability of the fixed solution is notably better than that of the float solution. Improvements of 48.15% and 27.9% were determined for the IENG–USN8 and WAB2–USN8 time links, respectively.

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