New 3D-Mapping-Aided Approach for User Integrity Monitoring in Urban Environments using a Nonparametric Positioning Errors Modeling

2017 ◽  
Author(s):  
N. Kbayer ◽  
M. Sahmoudi
Keyword(s):  
Urban Environments ◽  
3D Mapping ◽  
Integrity Monitoring ◽  
Positioning Errors

scholarly journals Positioning and integrity monitoring using the new DFMC SBAS service in the road transport

2020 ◽  
Author(s):  
Kan Wang ◽  
Ahmed El-Mowafy
Keyword(s):  
Urban Areas ◽  
Road Transport ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
Performance Standard ◽  
Civil Aviation ◽  
Dual Frequency ◽  
Test Bed ◽  
Integrity Monitoring ◽  
Positioning Errors

<p>Australia and New Zealand has initiated a two-year test-bed in 2017 for the new generation of Satellite-Based Augmentation System (SBAS). In addition to the legacy L1 service, the test-bed broadcasts SBAS messages through L5 to support the dual-frequency multi-constellation (DFMC) service for GPS and Galileo. Furthermore, PPP corrections were also sent via L1 and L5 to support the PPP service for dual-frequency GPS users and GPS/Galileo users, respectively.</p><p>The positioning and integrity monitoring process are currently defined for the aeronautical DFMC SBAS service in [1]. For land applications in road transport, users may encounter problems in complicated measurement environments like urban areas, e.g., more complicated multipath effects and frequent filter initializations of the carrier-smoothed code observations. In this study, a new weighting model related to the elevation angles, the signal-to-noise ratios (SNRs) and the filter smoothing time is developed. The weighting coefficients adjusting the impacts of these factors are studied for the open-sky, the suburban and the urban scenarios. Applying the corresponding weighting models, the overbounding cumulative distribution functions (CDFs) of the weighted noise/biases are searched and proposed for these scenarios.</p><p>Using real data collected under different measurement scenarios mentioned above, the DFMC SBAS positioning errors and protection levels are computed in the horizontal direction based on the proposed weighting models and the proposed overbounding CDFs. The results are compared with the case applying only the traditional elevation-dependent weighting model. While the positioning accuracy and protection levels did not change much for the open-sky scenario, the RMS of the positioning errors and the average protection levels are found to be reduced in both the suburban and urban scenarios. </p><p>[1] EUROCAE (2019) Minimum operational performance standard for Galileo/global positioning system/satellite-based augmentation system airborne equipment. The European Organisation for civil aviation equipment, ED-259, February 2019</p>

scholarly journals Integrity Monitoring for Horizontal RTK Positioning: New Weighting Model and Overbounding CDF in Open-Sky and Suburban Scenarios

2020 ◽  
Vol 12 (7) ◽  
pp. 1173 ◽  
Author(s):  
Kan Wang ◽  
Ahmed El-Mowafy ◽  
Chris Rizos ◽  
Jinling Wang
Keyword(s):  
Ambiguity Resolution ◽  
Elevation Angle ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
Correlated Errors ◽  
Short Baseline ◽  
Integrity Monitoring ◽  
Misleading Information ◽  
Spatially Correlated ◽  
Positioning Errors

Integrity monitoring is an essential task for ensuring the safety of positioning services. Under a selected probability of hazardous misleading information, the protection levels (PLs) are computed according to a considered threat model to bound the positioning errors. A warning message is sent to users when the PL exceeds a pre-set alert limit (AL). In the short-baseline real-time relative kinematic positioning, the spatially correlated errors, such as the the orbital errors and the atmospheric delays are significantly reduced. However, the remaining atmospheric residuals and the multipath that are not considered in the observation model could directly bias the positioning results. In this contribution, these biases are analysed with the focus put on the multipath effects in different measurement environments. A new observation weighting model considering both the elevation angle and the signal-to-noise ratios is developed and their impacts on the positional results are investigated. The coefficients of the proposed weighting model are determined for the open-sky and the suburban scenarios with the positional benefits maximised. Next, the overbounding excess-mass cumulative distribution functions (EMCs) are searched on the between-receiver level for the weighted phase and code observations in these two scenarios. Based on the mean and standard deviations of these EMCs, horizontal protection levels (HPLs) are computed for the ambiguity-fixed solutions of real experiments. The HPLs are compared with the horizontal positioning errors (HPEs) and the horizontal ALs (HALs). Using the sequential exclusion algorithm developed for the ambiguity resolution in this contribution, the full ambiguity resolution can be achieved in around 100% and 95% of the time for the open-sky and the suburban scenarios, respectively. The corresponding HPLs of the ambiguity-fixed solutions are at the sub-dm to dm-level for both scenarios, and all the valid ambiguity-fixed HPLs are below a HAL of 0.5 m. For the suburban scenario with more complicated multipath environments, the HPLs increase by considering extra biases to account for multipath under a certain elevation threshold. In complicated multipath environments, when this elevation threshold is set to 30 degrees, the availability of the ambiguity-fixed solutions could decrease to below 50% for applications requiring HAL as low as 0.1 m.

Towards Efficient and Robust LiDAR-based 3D Mapping in Urban Environments

2020 ◽  
Author(s):  
Ruike Ren ◽  
Hao Fu ◽  
Xiaochang Hu ◽  
Hanzhang Xue ◽  
Xiaohui Li ◽  
...  
Keyword(s):  
Urban Environments ◽  
3D Mapping

A Computation Effective Range-Based 3D Mapping Aided GNSS with NLOS Correction Method

2020 ◽  
Vol 73 (6) ◽  
pp. 1202-1222 ◽  
Author(s):  
Hoi-Fung Ng ◽  
Guohao Zhang ◽  
Li-Ta Hsu
Keyword(s):  
Ray Tracing ◽  
Urban Areas ◽  
Low Cost ◽  
Three Dimensional ◽  
Correction Method ◽  
Satellite System ◽  
Urban Environments ◽  
3D Mapping ◽  
Gnss Positioning ◽  
Positioning Method

Global navigation satellite system (GNSS) positioning in dense urban areas remains a challenge due to the signal reflection by buildings, namely multipath and non-line-of-sight (NLOS) reception. These effects degrade the performance of low-cost GNSS receivers such as in those smartphones. An effective three-dimensional (3D) mapping aided GNSS positioning method is proposed to correct the NLOS error. Instead of applying ray-tracing simulation, the signal reflection points are detected based on a skyplot with the surrounding building boundaries. The measurements of the direct and reflected signals can thus be simulated and further used to determine the user's position based on the measurement likelihood between real measurements. Verified with real experiments, the proposed algorithm is able to reduce the computational load greatly while maintaining a positioning accuracy within 10 metres of error in dense urban environments, compared with the conventional method of ray-tracing based NLOS corrected positioning.

scholarly journals Integrity Analysis for GPS-Based Navigation of UAVs in Urban Environment

Robotics ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 66
Author(s):  
Oguz Kagan Isik ◽  
Juhyeon Hong ◽  
Ivan Petrunin ◽  
Antonios Tsourdos
Keyword(s):  
Urban Environment ◽  
Urban Areas ◽  
Environmental Parameters ◽  
Urban Environments ◽  
Rate Of Change ◽  
Global Navigation Satellite Systems ◽  
Integrity Monitoring ◽  
Satellite Systems ◽  
Joint Consideration ◽  
Global Navigation Satellite

The increasing use of Unmanned Aerial Vehicles (UAVs) in safety-critical missions in both civilian and military areas demands accurate and reliable navigation, where one of the key sources of navigation information is presented by Global Navigation Satellite Systems (GNSS). In challenging conditions, for example, in urban areas, the accuracy of GNSS-based navigation may degrade significantly due to user-satellite geometry and obscuration issues without being noticed by the user. Therefore, considering the essentially dynamic rate of change in this type of environment, integrity monitoring is of critical importance for understanding the level of trust we have in positioning and timing data. In this paper, the dilution of precision (DOP) coefficients under nominal and challenging conditions were investigated for the purpose of integrity monitoring in urban environments. By analyzing positioning information in a simulated urban environment using a software-based GNSS receiver, the integrity monitoring approach based on joint consideration of GNSS observables and environmental parameters has been proposed. It was shown that DOP coefficients, when considered together with a number of visible satellites and cut-off elevations specific to the urban environment carry valuable integrity information that is difficult to get using existing integrity monitoring approaches. This has allowed generating indirect integrity measures based on cut-off elevation and satellite visibility that can be used for UAV path planning and guidance in urban environments.

Evaluation for Vehicle Positioning in Urban Environment Using QZSS Enhancement Function

2012 ◽  
Vol 24 (5) ◽  
pp. 894-901
Author(s):  
Mitsunori Kitamura ◽  
◽  
Taro Suzuki ◽  
Yoshiharu Amano ◽  
Takumi Hashizume ◽  
...  
Keyword(s):  
Urban Environment ◽  
Performance Enhancement ◽  
Elevation Angle ◽  
Satellite System ◽  
High Elevation ◽  
Urban Environments ◽  
Gps Positioning ◽  
Positioning Errors ◽  
Evaluation Test ◽  
Gps Accuracy

In this paper, we have evaluated the performance and availability enhancement of Quasi-Zenith Satellite System (QZSS) in urban environments. In urban environments, QZSS can be expected to be fairly effective because of the high elevation angle of satellite and enhancement functions. Therefore, we conducted performance and availability enhancement evaluation tests to verify thus. In performance enhancement evaluation test, in order to evaluate the improvement of GPS accuracy by L1 Submeter-class Augmentation with Integrity Function (L1-SAIF) broadcasted by QZSS satellite, we compared the positioning errors of only GPS positioning and L1-SAIF positioning in open sky environment. In availability enhancement evaluation test, we performed the static and kinematic observation test. In static observation test, in order to evaluate the improvement of GPS accuracy by availability enhancement, we observed GPS and QZSS statically in narrow-sky environment. And we compared the positioning errors of only GPS positioning and positioning using availability enhancement. In kinematic observation test, in order to evaluate the availability of QZSS based on the visibility of QZSS satellite in urban environment, we observed QZSS and SBAS from moving vehicle. And we compared the visibility of QZSS and SBAS satellites. From these evaluation tests, it was confirmed that the performance and availability enhancement of QZSS have high availability and effectiveness.

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