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Journal of Global Positioning Systems Vol. 17, No. 2, 2021 |
Cover |
Journal of Global Positioning Systems
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JGPS Team Structure, Copyright and Table of Contents |
JGPS Team Structure, Copyright
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1. On long-baseline relative positioning with BDS-2/BDS-3/GPS data |
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Xiaoting Kei, Huizhong Zhu, Jingfa Zhang and Yangyang Lu
BeiDou global navigation satellite system
(BDS-3) reached the global coverage in June 2020.
To study the performance of the precise relative
positioning using the BDS-3 alone and the
improvement due to adding BDS-3 satellites to
BDS-2 and GPS, this paper analysed the data of
033-039d provided by the MGEX in 2021. The
fusion of BDS-2, BDS-3 and GPS data was
conducted for static and dynamic high-precision
long-baseline solution experiments. The influence of
the individual BDS-2 / BDS-3 / GPS and by adding
BDS-3 satellites to BDS-2 and GPS on precise
relative positioning convergence speed and
positioning accuracy were analyzed, respectively.
The experimental results show that the current BDS-3
positioning performance (convergence speed and
positioning accuracy) is similar to GPS, and the
BDS-3 satellites effectively improve the positioning
convergence speed upon BDS-2 and GPS. In the
static positioning processing mode, with the aid of
the BDS-3 satellites, the RMS (Root-Mean-Square)
of the positioning errors using GPS only and the
combination of BDS-2 and GPS was increased only
by 20 % in the up direction, and for the BDS-2
system alone, the positioning accuracies in the E, N
and U components were increased by 60%, 71% and
65%, respectively. In the dynamic positioning
processing mode, after the addition of BDS-3
satellites, the positioning accuracies using GPS and
GPS+BDS-2 in the E, N and U components were
improved by about 15 %, 23 % and 23 %,
respectively, and the BDS-2 positioning accuracies were improved by about 46 %, 38 % and 36 % in the
E, N and U components, respectively.
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2. Multi-GNSS RTK positioning with integer ambiguity resolution: From double-differenced to single differenced |
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Xiaolong Mi, Baocheng Zhang and Yunbin Yuan
The development of global navigation satellite
systems (GNSS), especially BeiDou navigation
satellite system with global coverage (BDS-3), has
brought benefits for high-precision positioning.
Real-time kinematic (RTK) positioning based on
double-differenced (DD) observations has been
widely used in high-precision positioning as common
errors are eliminated. However, the biases at the
receiver-end, which can be dynamically constrained,
are also eliminated during the DD process. Therefore,
it makes sense to turn RTK from DD to
single-differenced (SD) as the advantages of dynamic
constraints of the receiver biases can be exploited. In
this contribution, we first present RTK models based
on DD observations suitable for short, medium and
long baselines. Then, based on SD observations, the
full-rank RTK models are constructed with the
S-system theory. Using observations from GPS,
BDS-3 and Galileo, we first demonstrate the
short-term stability of receiver-related biases. The SD
RTK positioning performance with the stability of
those receiver-related biases regarding integer
ambiguity resolution success rate and positioning
accuracy are analyzed. With those biases, RTK can achieve high performance, and this is more
advantageous in multi-GNSS scenarios.
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3. Research on the UWB High Precision Indoor Positioning Method with the Heterogeneous Information Constraints |
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Nan Guo, Wei Jiang, Jing Li, Fei Liu and Jie Dong
There are many obstacles in the UWB
indoor positioning, such as installation location
limitation of base stations, non-line-of-sight and so
forward. In this paper, the high-precision indoor
positioning model was discussed, and then the UWB
indoor positioning method was given based on the
heterogeneous data constraints, such as PDR, map
and vision. Three indoor positioning models, the
kinematic adaptive robust EKF UWB model based on
the gain matrix, the UWB/PDR/Map coupled model,
and the UWB/Vision fusion model were built and
assessed, respectively. Afterward, the precision and
the potential application scenarios of the three models
were discussed via the practical tests. The test results
showed that, with our method, the overall positioning
accuracy reached around ¡À0.2 m under the conditions
of the full or partial UWB signal coverage, available
or interrupted line-of-sight, or undergoing other
situational challenges such as the sparse texture and
the continuous variation of the light strength.
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4. A Comparative Analysis on Inter-frequency Data Quality of Quad-constellation GNSS on a Smartphone |
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Yanjie Li and Changsheng Cai
This paper comprehensively analyzes
the inter-frequency data quality of the
quad-constellation Global Navigation Satellite
System (GNSS) of GPS, GLONASS, BDS and
Galileo on a smartphone. A series of indices, i.e. the
number of visible satellites, data integrity rate,
multipath, carrier-to-noise ratio (C/No), cycle-slip
ratio and observation residuals, are employed to
evaluate the data quality with a comparison between
different constellations and frequencies. Experiments
were conducted using the firstly released
dual-frequency smartphone of Xiaomi Mi8. The
results show that the GPS and BDS exhibit the best
tracking performance in an open-sky environment
with an average of 7 observed satellites at each epoch,
which is 3 or 4 satellites more than the Galileo and
GLONASS. In addition, the GPS data integrity rate is
higher than the other constellations by about
20%-25%. The GPS suffers a multipath effect two
times larger than the Galileo on the L1/E1
frequencies, but they are almost equal on the L5/E5a
frequencies. For all four constellations, the C/No is
mostly concentrated at 20-35 dB-Hz. Further, the
C/No on the L1/E1 frequencies increases by 3-4
dB-Hz over the L5/E5a frequencies. The GLONASS
observations exhibit the most serious cycle slip
occurrence rate at a ratio of 100, which is
significantly larger than the other constellations.
Regarding the residuals, the phase RMS residuals for
all four constellations are at a few millimeters,
whereas the pseudorange residuals of GLONASS are the most prominent with an RMS of over 6 m, which
is 3-4 times larger than the other constellations. The
precise point positioning (PPP) results show that the
convergence time and positioning accuracy can be
effectively improved by adding GPS and Galileo data
at L5/E5a.
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5. Analysis of real-time multi-GNSS satellite products of Wuhan University for rapid response of precise positioning |
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Qi Zhang, Ran Zeng, Shaoming Xin and Xing Zhou
When users need to quickly process GNSS
data, they often need the satellite orbit and clock
products with the minimum latency and the highest
precision, and it is a good solution to receive the
real-time satellite RTCM SSR correction stream to
recover the precise satellite orbit and clock products
in real time and then store them in an offline
repository for rapid response of precise positioning.
In this paper, the real-time multi-GNSS orbit and
clock RTCM SSR correction stream broadcast by
SSRC00WHU0 mountpoint of Wuhan University is
used to recover precise satellite orbit and clock
products in real time. First, the seven-day orbit files
and clock files were obtained and stored locally, and
compared with the final MGEX precise satellite orbit
and clock products. The results show that the
real-time orbit and clock products of GPS and
Galileo satellites have the best accuracy, followed by
GLONASS satellites and BDS satellites. The
real-time orbit products can reach the accuracy level
of 5 cm for GPS satellites, 8 cm for Galileo satellites,
15 cm for GLONASS satellites and 16 cm for BDS-3
satellites, and the real-time clock products can reach
the accuracy level of 0.43 ns for GPS satellites, 0.44
ns for Galileo satellites, 0.91 ns for GLONASS
satellites and 3.14 ns for BDS satellites. Then, the
observation data of 20 IGS stations randomly
distributed around the world from DOY 150 to 156 in
2021 were processed by static precise point
positioning (PPP) mode using the recovered real-time
products. The results show that the average positioning accuracy can reach 1.57 cm, 0.76 cm and
1.67 cm in east, north and up direction for static PPP,
respectively. Finally, using the recovered real-time
products and the final products, the GPS observation
data collected in aviation were processed in pseudo
real-time in a kinematic mode. The results show that
the RMSs of positioning errors are 8.5 cm, 2.4 cm
and 16.5 cm in the east, north and up direction,
respectively. In addition, one-day multi-GNSS
observation data at 20 IGS stations were processed in
a kinematic PPP mode, and the results show that the
average positioning accuracy is 3.11 cm, 2.04 cm and
4.94 cm in east, north and up directions.
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6. A Survey of Simultaneous Localization and Mapping with an Envision in 6G Wireless Networks |
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Baichuan Huang, Jun Zhao, Sheng Luo and Jingbin Liu
Simultaneous Localization and Mapping
(SLAM) achieves the purpose of simultaneous
positioning and map construction based on
self-perception. The paper makes an overview in
SLAM including Lidar SLAM, visual SLAM, and
their fusion. For Lidar or visual SLAM, the survey
illustrates the basic type and product of sensors, open
source system in sort and history, deep learning
embedded, the challenge and future. Additionally,
visual inertial odometry is supplemented. For Lidar
and visual fused SLAM, the paper highlights the
multi-sensors calibration, the fusion in hardware, data,
task layer. The open question and an envision in 6G
wieless networks with SLAM end the paper. The
contributions of this paper can be summarized as
follows: the paper provides a high quality and
full-scale overview in SLAM. It's very friendly for
new researchers to hold the development of SLAM
and learn it very obviously. Also, the paper can be
considered as dictionary for experienced researchers
to search and find new interested orientation.
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ABSTRACTS OF PHD DISSERTATIONS |
7. Generic Interferometric Synthetic Aperture Radar Atmospheric Correction Model and Its Application to Co- and Post-Seismic Motions |
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Chen Yu, Newcastle University, UK
The Interferometric Synthetic Aperture Radar
(InSAR) technique has experienced a tremendous
development during the past 10 years that enables
research for mapping the Earth¡¯s surface movements
at larger scales and with smaller amplitudes than ever
before. Apart from already in orbit satellites such as
Sentinel-1A/B, Gaofen-3 and ALOS-2, many more
have been scheduled for the period from 2018 to 2025
(e.g., Sentinel-1C/D, Gaofen-3B/C, RADARSAT
Constellation). One of the most critical challenges
when utilizing these data, hampering all techniques
that require microwaves passing through the Earth¡¯s
atmosphere, is to mitigate their atmospheric effects
due to the spatial and temporal variations of water
vapour. This effect may dominate over large scales
and completely mask the actual displacement due to
tectonic or volcanic deformation. Accordingly, the aim
of this thesis is to provide a generic atmospheric
correction model through an operational highresolution numerical weather model, the Global
Positioning System (GPS), and/or their combination,
with particular application to co- and post-seismic
studies.
Previous attempts that used observations from GPS
and Numerical Weather Models (NWMs) are limited
by (i) the availability (and distribution) of GPS
stations; (ii) the time difference between NWM and
radar observations; and (iii) the difficulties in quantifying their performance. To overcome these
limitations, we have developed the Iterative
Tropospheric Decomposition (ITD) model to reduce
the coupling effects of the troposphere turbulence and
stratification and hence achieve similar performances
over flat and mountainous terrains. High-resolution
European Centre for Medium-Range Weather
Forecasts (ECMWF) and GPS-derived tropospheric
delays were properly integrated by investigating the
GPS network geometry and topography variations.
These led to a generic atmospheric correction model
(GACOS) with a range of notable features: (i) global
coverage, (ii) all-weather, all-time usability, (iii)
available with a maximum of two-day latency, and (iv)
indicators available to assess the model¡¯s performance
and feasibility.
The generic atmospheric correction model enables
the investigation of the small magnitude co-seismic
deformation of the 2017 Mw-6.4 Nyingchi earthquake
from InSAR observations in spite of substantial
atmospheric contamination. It can also minimize the
temporal correlations of InSAR atmospheric delays so
that reliable velocity maps over large spatial extents
can be achieved. Its application to the post-seismic
motion following the 2016 Kaikoura earthquake shows
a success to recover the time-dependent afterslip
distribution, which in turn evidences the deep inactive
subduction slip mechanism. This procedure can be
used to map surface deformation in other scenarios including volcanic eruptions, tectonic rifting, cracking,
and city subsidence.
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8. Integer Ambiguity Resolution for Smartphone based multi-GNSS data |
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Guangcai Li, Wuhan University
Smartphones are integrated with consumer-grade
GNSS chips and inertial sensors, providing an effective
research platform for tapping the potential of
miniaturized, low-cost sensors for high-precision
positioning. However, for the GNSS observations of
smartphones, phase biases generated by the low-cost
GNSS chips and severe multipath errors introduced by
the embedded antenna, resulting in unresolved carrier
phase ambiguity.
To solve these problems, this dissertation conducts
an in-depth study on the key technologies of GNSS
ambiguity resolution and other high-precision
positioning for smartphones. The error characteristics
of smartphone GNSS observations were analyzed, the
carrier phase bias estimation method and multipath
mitigation method were proposed, and the smartphone
GNSS centimeter-level ambiguity-fixed solutions were
obtained. Based on this, we further explored methods
such as synchronous integration of smartphone GNSS
with the accelerometer, and obtained higher precision
and higher resolution positioning results. As a result,
the feasibility of centimeter-level high-precision
positioning using consumer-grade GNSS chips,
antennas and inertial sensors embedded in smartphones
was demonstrated. Meanwhile, these works can provide
theoretical methods and technical support for highprecision positioning using miniaturized, low-cost GNSS and inertial sensors.
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9. An investigation on short-term prediction of serve weather events based on GNSS-derived atmospheric information |
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Haobo Li, China University of Mining and Technology
In recent years, the increasing frequency of
natural disasters caused by various types of severe
weather events (SWEs) has resulted in more and
more damage and losses to properties and livelihoods.
These phenomena highlight a pressing need to
understand the intrinsic nature of these events and
develop reliable and robust methods for the
nowcasting and very short-range forecasting (VSRF)
of SWEs, thus to prevent and mitigate the influences
brought by all kinds of natural disasters. Facing with
the high demand of the VSRF of SWEs, it is
necessary to obtain and use various kinds of
meteorological data with high accuracy and high
spatiotemporal resolution in an effective way.
Atmospheric water vapor (WV), which is recognized
as an essential climate variable, greatly affects the
atmosphere stability, the hydrological and energy
cycles, and the formation of cloud and rainfall. As
one of the most active components in the atmosphere,
the evolution of WV has significant implications for
determining the intensity, time and extent of potential
SWEs. Therefore, to refine the service for the
monitoring and detection of SWEs, it is of great
importance to obtain the amount of WV contained in
the atmosphere and capture its movements. However,the rapid change and dynamic characteristics of WV
make it an extremely difficult task to obtain its
accurate and timely spatiotemporal distributions in
the troposphere using traditional observing
techniques such as radiosonde, water vapor
radiometers, and etc. With the rapid deployment and
development for nearly four decades, the Global
Navigation Satellite Systems (GNSS) has been
widely used in the remote sensing of atmospheric
variables, e.g., zenith total delay (ZTD) and
precipitable water vapor (PWV). This is mainly due
to the high accuracy, high spatiotemporal resolution
and all-weather capability of GNSS observations.
Hence, the availability of atmospheric information
retrieved from GNSS has opened new avenues and
new possibilities for GNSS meteorological
applications of the detection of SWEs
This dissertation focuses on the retrieval of
GNSS-derived atmospheric products with high
accuracy and high spatiotemporal resolution, and
then apply them to the nowcasting and VSRF of
SWEs. The research include: the retrieval of
atmospheric products from ground-based GNSS radio
signals and their accuracy evaluation, the feature
analysis of atmospheric variables and their responses to SWEs, short-term prediction of SWEs using
threshold-based models, anomaly-based models and
back propagation neural network (BPNN) algorithm. .
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Back Cover |
Journal of Global Positioning Systems
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