Enabling robust and accurate navigation for UAVs using real-time GNSS precise point positioning and IMU integration

ABSTRACTAccurate navigation is required in many Unmanned Aerial Vehicle (UAV) applications. In recent years, GNSS Precise Point Positioning (PPP) has been recognised as an efficient approach for providing precise positioning services. In contrast to the widely used Real-Time Kinematic (RTK), PPP is independent of reference stations, which greatly broadens its scope of application. However, the accuracy and reliability of PPP can be significantly decreased by poor GNSS satellite geometry and outage. In response, a real-time four-constellation GNSS PPP is applied to improve the geometry in this work, and PPP is tightly coupled with an Inertial Measurement Unit (IMU) to smooth the position and velocity output, thus improving the robustness of the navigation solution. Experimental flight tests are carried out using a UAV in an open-sky area, and GNSS-challenged environments are simulated. The results show that the four-constellation GNSS PPP/IMU integration reduces the Root-Mean-Square (RMS) Three-Dimensional (3D) positioning and velocity error by 76.4% and 67.1%, respectively, in open sky with respect to the one-GNSS PPP. Under scenarios where GNSS measurements are insufficient, the coupled system can still provide continuous solutions. Moreover, the coupled PPP/IMU system can also maintain the convergence of PPP during GNSS-challenged periods and can greatly shorten the re-convergence period of PPP when the UAV returns to the open sky.

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GNSS-Warp Software for Real-Time Precise Point Positioning

Artificial Satellites ◽

10.1515/arsa-2015-0005 ◽

2015 ◽

Vol 50 (2) ◽

pp. 59-76 ◽

Cited By ~ 10

Author(s):

Hadaś Tomasz

Keyword(s):

Real Time ◽

Precise Point Positioning ◽

Static Mode ◽

Time Service ◽

The Real ◽

North East ◽

Satellite Geometry ◽

Point Positioning ◽

Performance Validation ◽

Mode A

Abstract On April 1, 2013 IGS launched the real-time service providing products for Precise Point Positioning (PPP). The availability of real-time makes PPP a very powerful technique to process GNSS signals in real-time and opens a new PPP applications opportunities. There are still, however, some limitations of PPP, especially in the kinematic mode. A significant change in satellite geometry is required to efficiently de-correlate troposphere delay, receiver clock offset, and receiver height. In order to challenge PPP limitations, the GNSS-WARP (Wroclaw Algorithms for Real-time Positioning) software has been developed from scratch at Wroclaw University of Environmental and Life Science in Poland. This paper presents the GNSS-WARP software itself and some results of GNSS data analysis using PPP and PPP-RTK (Real-Time Kinematic) technique. The results of static and kinematic processing in GPS only and GPS + GLONASS mode with final and real-time products are presented. Software performance validation in postprocessing mode confirmed that the software can be considered as a state-ofthe- art software and used for further studies on PPP algorithm development. The real-time positioning test made it possible to assess the quality of real-time coordinates, which is a few millimeters for North, East, Up in static mode, a below decimeter in kinematic mode. The accuracy and precision of height estimates in kinematic mode were improved by constraining the solution with an external, near real-time troposphere model. The software also allows estimation of real-time ZTD, however, the obtained precision of 11.2 mm means that further improvements in the software, real-time products or processing strategy are required.

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Precise Point Positioning using Multi-Constellation GNSS Observations for Kinematic Applications

Journal of Applied Geodesy ◽

10.1515/jag-2014-0021 ◽

2015 ◽

Vol 9 (1) ◽

Cited By ~ 12

Author(s):

Mahmoud Abd Rabbou ◽

Ahmed El-Rabbany

Keyword(s):

Urban Areas ◽

Precise Point Positioning ◽

Global Navigation Satellite Systems ◽

Test Scenario ◽

Satellite Systems ◽

Satellite Geometry ◽

Point Positioning ◽

Kinematic Ppp ◽

Gnss Measurements ◽

Global Navigation Satellite

AbstractTraditional precise point positioning (PPP) is commonly based on un-differenced ionosphere-free linear combination of Global Positioning System (GPS) observations. Unfortunately, for kinematic applications, GPS often experiences poor satellite visibility or weak satellite geometry in urban areas. To overcome this limitation, we developed a PPP model, which combines the observations of three global navigation satellite systems (GNSS), namely GPS, GLONASS and Galileo. Both un-differenced and between-satellite single-difference (BSSD) ionosphere-free linear combinations of pseudorange and carrier phase GNSS measurements are processed. The performance of the combined GNSS PPP solution is compared with the GPS-only PPP solution using a real test scenario in downtown Kingston, Ontario. Inter-system biases between GPS and the other two systems are also studied and obtained as a byproduct of the PPP solution. It is shown that the addition of GLONASS observations improves the kinematic PPP solution accuracy in comparison with that of GPS-only solution. However, the contribution of adding Galileo observations is not significant due to the limited number of Galileo satellites launched up to date. In addition, BSSD solution is found to be superior to that of traditional un-differenced model.

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Precise point positioning with GPS and Galileo broadcast ephemerides

GPS Solutions ◽

10.1007/s10291-021-01111-4 ◽

2021 ◽

Vol 25 (2) ◽

Author(s):

Luca Carlin ◽

André Hauschild ◽

Oliver Montenbruck

Keyword(s):

Precise Point Positioning ◽

Three Dimensional ◽

Test Results ◽

Process Noise ◽

Functional Models ◽

Ambiguity Estimation ◽

Point Positioning ◽

And Performance ◽

Range Error ◽

Space Range

AbstractFor more than 20 years, precise point positioning (PPP) has been a well-established technique for carrier phase-based navigation. Traditionally, it relies on precise orbit and clock products to achieve accuracies in the order of centimeters. With the modernization of legacy GNSS constellations and the introduction of new systems such as Galileo, a continued reduction in the signal-in-space range error (SISRE) can be observed. Supported by this fact, we analyze the feasibility and performance of PPP with broadcast ephemerides and observations of Galileo and GPS. Two different functional models for compensation of SISREs are assessed: process noise in the ambiguity states and the explicit estimation of a SISRE state for each channel. Tests performed with permanent reference stations show that the position can be estimated in kinematic conditions with an average three-dimensional (3D) root mean square (RMS) error of 29 cm for Galileo and 63 cm for GPS. Dual-constellation solutions can further improve the accuracy to 25 cm. Compared to standard algorithms without SISRE compensation, the proposed PPP approaches offer a 40% performance improvement for Galileo and 70% for GPS when working with broadcast ephemerides. An additional test with observations taken on a boat ride yielded 3D RMS accuracy of 39 cm for Galileo, 41 cm for GPS, and 27 cm for dual-constellation processing compared to a real-time kinematic reference solution. Compared to the use of process noise in the phase ambiguity estimation, the explicit estimation of SISRE states yields a slightly improved robustness and accuracy at the expense of increased algorithmic complexity. Overall, the test results demonstrate that the application of broadcast ephemerides in a PPP model is feasible with modern GNSS constellations and able to reach accuracies in the order of few decimeters when using proper SISRE compensation techniques.

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Simulation case study of deformations and landslides using real-time GNSS precise point positioning technique

Geomatics Natural Hazards and Risk ◽

10.1080/19475705.2015.1137243 ◽

2016 ◽

Vol 7 (6) ◽

pp. 1856-1873 ◽

Cited By ~ 6

Author(s):

Raquel M. Capilla ◽

José Luis Berné ◽

Angel Martín ◽

Raul Rodrigo

Keyword(s):

Real Time ◽

Precise Point Positioning ◽

Positioning Technique ◽

Point Positioning

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Precise Point Positioning Using the Regional BeiDou Navigation Satellite Constellation

Journal of Navigation ◽

10.1017/s0373463313000842 ◽

2014 ◽

Vol 67 (3) ◽

pp. 523-537 ◽

Cited By ~ 7

Author(s):

Aigong Xu ◽

Zongqiu Xu ◽

Xinchao Xu ◽

Huizhong Zhu ◽

Xin Sui ◽

...

Keyword(s):

Real Time ◽

Precise Point Positioning ◽

Satellite System ◽

Convergence Time ◽

Asia Pacific ◽

Satellite Orbits ◽

Navigation Satellite ◽

Asia Pacific Region ◽

Point Positioning

On 27 December 2012 it was announced officially that the Chinese Navigation Satellite System BeiDou (BDS) was able to provide operational services over the Asia-Pacific region. The quality of BDS observations was confirmed as comparable with those of GPS, and relative positioning in static and kinematic modes were also demonstrated to be very promising. As Precise Point Positioning (PPP) technology is widely recognized as a method of precise positioning service, especially in real-time, in this contribution we concentrate on the PPP performance using BDS data only. BDS PPP in static, kinematic and simulated real-time kinematic mode is carried out for a regional network with six stations equipped with GPS- and BDS-capable receivers, using precise satellite orbits and clocks estimated from a global BDS tracking network. To validate the derived positions and trajectories, they are compared to the daily PPP solution using GPS data. The assessment confirms that the performance of BDS PPP is very comparable with GPS in terms of both convergence time and accuracy.

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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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Enhancing real-time precise point positioning time and frequency transfer with receiver clock modeling

GPS Solutions ◽

10.1007/s10291-018-0814-y ◽

2018 ◽

Vol 23 (1) ◽

Cited By ~ 14

Author(s):

Yulong Ge ◽

Feng Zhou ◽

Tianjun Liu ◽

WeiJin Qin ◽

Shengli Wang ◽

...

Keyword(s):

Real Time ◽

Precise Point Positioning ◽

Receiver Clock ◽

Frequency Transfer ◽

Point Positioning ◽

Positioning Time

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Performance Analysis of Static Precise Point Positioning Using Open-Source GAMP

Artificial Satellites ◽

10.2478/arsa-2020-0004 ◽

2020 ◽

Vol 55 (2) ◽

pp. 41-60

Author(s):

Jabir Shabbir Malik

Keyword(s):

Performance Analysis ◽

Open Source ◽

Observational Data ◽

Precise Point Positioning ◽

Three Dimensional ◽

Satellite System ◽

International Gnss Service ◽

Positioning Accuracy ◽

Position Accuracy ◽

Point Positioning

AbstractIn addition to Global Positioning System (GPS) constellation, the number of Global Navigation Satellite System (GLONASS) satellites is increasing; it is now possible to evaluate and analyze the position accuracy with both the GPS and GLONASS constellation. In this article, statistical analysis of static precise point positioning (PPP) using GPS-only, GLONASS-only, and combined GPS/GLONASS modes is evaluated. Observational data of 10 whole days from 10 International GNSS Service (IGS) stations are used for analysis. Position accuracy in east, north, up components, and carrier phase/code residuals is analyzed. Multi-GNSS PPP open-source package is used for the PPP performance analysis. The analysis also provides the GNSS researchers the understanding of the observational data processing algorithm. Calculation statistics reveal that standard deviation (STD) of horizontal component is 3.83, 13.80, and 3.33 cm for GPS-only, GLONASS-only, and combined GPS/GLONASS PPP solutions, respectively. Combined GPS/GLONASS PPP achieves better positioning accuracy in horizontal and three-dimensional (3D) accuracy compared with GPS-only and GLONASS-only PPP solutions. The results of the calculation show that combined GPS/GLONASS PPP improves, on an average, horizontal accuracy by 12.11% and 60.33% and 3D positioning accuracy by 10.39% and 66.78% compared with GPS-only and GLONASS-only solutions, respectively. In addition, the results also demonstrate that GPS-only solutions show an improvement of 54.23% and 62.54% compared with GLONASS-only PPP mode in horizontal and 3D components, respectively. Moreover, residuals of GLONASS ionosphere-free code observations are larger than the GPS code residuals. However, phase residuals of GPS and GLONASS phase observations are of the same magnitude.

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GPS AND GLONASS COMBINED STATIC PRECISE POINT POSITIONING (PPP)

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xli-b1-483-2016 ◽

2016 ◽

Vol XLI-B1 ◽

pp. 483-488 ◽

Cited By ~ 1

Author(s):

D. Pandey ◽

R. Dwivedi ◽

O. Dikshit ◽

A. K. Singh

Keyword(s):

Precise Point Positioning ◽

Rapid Development ◽

Three Dimensional ◽

Global Navigation Satellite Systems ◽

Open Pit ◽

Positioning Accuracy ◽

Dilution Of Precision ◽

Satellite Visibility ◽

Point Positioning ◽

Gps Observations

With the rapid development of multi-constellation Global Navigation Satellite Systems (GNSSs), satellite navigation is undergoing drastic changes. Presently, more than 70 satellites are already available and nearly 120 more satellites will be available in the coming years after the achievement of complete constellation for all four systems- GPS, GLONASS, Galileo and BeiDou. The significant improvement in terms of satellite visibility, spatial geometry, dilution of precision and accuracy demands the utilization of combining multi-GNSS for Precise Point Positioning (PPP), especially in constrained environments. Currently, PPP is performed based on the processing of only GPS observations. Static and kinematic PPP solutions based on the processing of only GPS observations is limited by the satellite visibility, which is often insufficient for the mountainous and open pit mines areas. One of the easiest options available to enhance the positioning reliability is to integrate GPS and GLONASS observations. This research investigates the efficacy of combining GPS and GLONASS observations for achieving static PPP solution and its sensitivity to different processing methodology. Two static PPP solutions, namely standalone GPS and combined GPS-GLONASS solutions are compared. The datasets are processed using the open source GNSS processing environment <i>gLAB</i> 2.2.7 as well as <i>magicGNSS</i> software package. The results reveal that the addition of GLONASS observations improves the static positioning accuracy in comparison with the standalone GPS point positioning. Further, results show that there is an improvement in the three dimensional positioning accuracy. It is also shown that the addition of GLONASS constellation improves the total number of visible satellites by more than 60% which leads to the improvement of satellite geometry represented by Position Dilution of Precision (PDOP) by more than 30%.

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