scholarly journals GNSS/LiDAR-Based Navigation of an Aerial Robot in Sparse Forests

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4061 ◽  
Author(s):  
Antonio C. B. Chiella ◽  
Henrique N. Machado ◽  
Bruno O. S. Teixeira ◽  
Guilherme A. S. Pereira
Keyword(s):  
Autonomous Navigation ◽  
Unscented Kalman Filter ◽  
Unmanned Vehicles ◽  
Global Navigation Satellite Systems ◽  
Fusion Algorithm ◽  
Forest Environment ◽  
Satellite Systems ◽  
Aerial Robot ◽  
Robust Adaptive ◽  
Global Navigation Satellite

Autonomous navigation of unmanned vehicles in forests is a challenging task. In such environments, due to the canopies of the trees, information from Global Navigation Satellite Systems (GNSS) can be degraded or even unavailable. Also, because of the large number of obstacles, a previous detailed map of the environment is not practical. In this paper, we solve the complete navigation problem of an aerial robot in a sparse forest, where there is enough space for the flight and the GNSS signals can be sporadically detected. For localization, we propose a state estimator that merges information from GNSS, Attitude and Heading Reference Systems (AHRS), and odometry based on Light Detection and Ranging (LiDAR) sensors. In our LiDAR-based odometry solution, the trunks of the trees are used in a feature-based scan matching algorithm to estimate the relative movement of the vehicle. Our method employs a robust adaptive fusion algorithm based on the unscented Kalman filter. For motion control, we adopt a strategy that integrates a vector field, used to impose the main direction of the movement for the robot, with an optimal probabilistic planner, which is responsible for obstacle avoidance. Experiments with a quadrotor equipped with a planar LiDAR in an actual forest environment is used to illustrate the effectiveness of our approach.

scholarly journals Practical Modeling of GNSS for Autonomous Vehicles in Urban Environments

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4236
Author(s):  
Woosik Lee ◽  
Hyojoo Cho ◽  
Seungho Hyeong ◽  
Woojin Chung
Keyword(s):  
Motion Estimation ◽  
Autonomous Vehicles ◽  
Autonomous Navigation ◽  
Urban Environments ◽  
Global Navigation Satellite Systems ◽  
Navigation Satellite ◽  
Key Technology ◽  
Satellite Systems ◽  
Agricultural Robots ◽  
Global Navigation Satellite

Autonomous navigation technology is used in various applications, such as agricultural robots and autonomous vehicles. The key technology for autonomous navigation is ego-motion estimation, which uses various sensors. Wheel encoders and global navigation satellite systems (GNSSs) are widely used in localization for autonomous vehicles, and there are a few quantitative strategies for handling the information obtained through their sensors. In many cases, the modeling of uncertainty and sensor fusion depends on the experience of the researchers. In this study, we address the problem of quantitatively modeling uncertainty in the accumulated GNSS and in wheel encoder data accumulated in anonymous urban environments, collected using vehicles. We also address the problem of utilizing that data in ego-motion estimation. There are seven factors that determine the magnitude of the uncertainty of a GNSS sensor. Because it is impossible to measure each of these factors, in this study, the uncertainty of the GNSS sensor is expressed through three variables, and the exact uncertainty is calculated. Using the proposed method, the uncertainty of the sensor is quantitatively modeled and robust localization is performed in a real environment. The approach is validated through experiments in urban environments.

scholarly journals Performance Evaluation of GPS Auto-Surveying Techniques

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7374
Author(s):  
João Manito ◽  
José Sanguino
Keyword(s):  
Kalman Filter ◽  
Least Squares ◽  
Unscented Kalman Filter ◽  
Weighted Least Squares ◽  
Base Station ◽  
Global Navigation Satellite Systems ◽  
Precise Position ◽  
Satellite Systems ◽  
Global Navigation Satellite ◽  
Position Estimate

With the increase in the widespread use of Global Navigation Satellite Systems (GNSS), increasing numbers of applications require precise position data. Of all the GNSS positioning methods, the most precise are those that are based in differential systems, such as Differential GNSS (DGNSS) and Real-Time Kinematics (RTK). However, for absolute positioning, the precision of these methods is tied to their reference position estimates. With the goal of quickly auto-surveying the position of a base station receiver, four positioning methods are analyzed and compared, namely Least Squares (LS), Weighted Least Squares (WLS), Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF), using only pseudorange measurements, as well as the Hatch Filter and position thresholding. The research results show that the EKF and UKF present much better mean errors than LS and WLS, with an attained precision below 1 m after about 4 h of auto-surveying. The methods that presented the best results are then tested against existing implementations, showing them to be very competitive, especially considering the differences between the used receivers. Finally, these results are used in a DGNSS test, which verifies a significant improvement in the position estimate as the base station position estimate improves.

Astronomical Vessel Position Determination Utilizing the Optical Super Wide Angle Lens Camera

2014 ◽  
Vol 67 (4) ◽  
pp. 633-649 ◽  
Author(s):  
Chong-hui Li ◽  
Yong Zheng ◽  
Chao Zhang ◽  
Yu-Lei Yuan ◽  
Yue-Yong Lian ◽  
...  
Keyword(s):  
Autonomous Navigation ◽  
Estimation Method ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Celestial Navigation ◽  
Wide Angle Lens ◽  
Celestial Bodies ◽  
Determination System ◽  
Fisheye Camera ◽  
Global Navigation Satellite

Celestial navigation is an important type of autonomous navigation technology which could be used as an alternative to Global Navigation Satellite Systems (GNSS) when a vessel is at sea. After several centuries of development, a variety of astronomical vessel position (AVP) determination methods have been invented, but the basic concepts of these methods are all based on angular observations with a device such as a sextant, which has disadvantages including low accuracy, manual operation, and a limited period of observation. This paper proposes a new method that utilises a fisheye camera to image the celestial bodies and horizon simultaneously. Then, we calculate the obliquity of the fisheye camera's principal optical axis according to the image coordinates of the horizon. Next, we calculate the altitude of the celestial bodies according to the image coordinates of the celestial bodies and the obliquity. Finally, the AVP is determined by the altitudes according to the robust estimation method. Experimental results indicate that this method not only could realize automation and miniaturization of the AVP determination system, but could also greatly improve the efficiency of celestial navigation.

scholarly journals THE HANDHELD MOBILE LASER SCANNERS AS A TOOL FOR ACCURATE POSITIONING UNDER FOREST CANOPY

2020 ◽  
Vol XLIII-B1-2020 ◽  
pp. 211-218 ◽  
Author(s):  
J. Chudá ◽  
M. Hunčaga ◽  
J. Tuček ◽  
M. Mokroš
Keyword(s):  
Forest Canopy ◽  
Sustainable Forest Management ◽  
Environmental Data ◽  
Global Navigation Satellite Systems ◽  
Forest Environment ◽  
Positional Accuracy ◽  
Satellite Systems ◽  
Localization And Mapping ◽  
Laser Scanners ◽  
Global Navigation Satellite

Abstract. Nowadays it is important to shift positional accuracy of object measurements under the forest canopy closer to the accuracy standards for land surveys due to the requirements in the field of ecosystem protection, sustainable forest management, property relations, and land register. Simultaneously, it is desirable to use the technology of environmental data acquisition which is not time consuming and cost demanding. Global Navigation Satellite Systems (GNSS) are the most used for positioning today. However, the usefulness and also the accuracy of the measurements with this technology depend on various factors (the strength of the GNSS signal, the geometric position of satellites, the multipath effect etc.). Based on the above mentioned facts, the usability of technology independent of GNSS indicates an ideal solution for positioning under the forest canopy. Several studies have studied the usability of Handheld Mobile Laser Scanners (HMLS) in complex environment. The goal of this paper was to verify a new data collection approach (HMLS with Simultaneous Localization and Mapping (SLAM) technology) for the forest environment practice. The main objective of our study was to reach a precision which complies with the accuracy standards for land surveys. The RMSE of derived positions from point cloud, produced by SLAM devices were 25.3 cm and 28.4 cm, for ZEB REVO and ZEB HORIZON, the handheld mobile laser SLAM scanners used in this study. ZEB HORIZON achieved twice as big accuracy of diameter of breast height (DBH) estimation as ZEB REVO.

scholarly journals GNSS Spoofing Detection Based on Coupled Visual/Inertial/GNSS Navigation System

Sensors ◽  
2021 ◽  
Vol 21 (20) ◽  
pp. 6769
Author(s):  
Nianzu Gu ◽  
Fei Xing ◽  
Zheng You
Keyword(s):  
Optimal Estimation ◽  
Estimation Algorithm ◽  
Unmanned Vehicles ◽  
Global Navigation Satellite Systems ◽  
Navigation Systems ◽  
Chi Square ◽  
Satellite Systems ◽  
Spoofing Detection ◽  
Chi Square Test ◽  
Global Navigation Satellite

Spoofing attacks are one of the severest threats for global navigation satellite systems (GNSSs). This kind of attack can damage the navigation systems of unmanned air vehicles (UAVs) and other unmanned vehicles (UVs), which are highly dependent on GNSSs. A novel method for GNSS spoofing detection based on a coupled visual/inertial/GNSS positioning algorithm is proposed in this paper. Visual inertial odometry (VIO) has high accuracy for state estimation in the short term and is a good supplement for GNSSs. Coupled VIO/GNSS navigation systems are, unfortunately, also vulnerable when the GNSS is subject to spoofing attacks. The method proposed in this article involves monitoring the deviation between the VIO and GNSS under an optimization framework. A modified Chi-square test triggers the spoofing alarm when the detection factors become abnormal. After spoofing detection, the optimal estimation algorithm is modified to prevent it being deceived by the spoofed GNSS data and to enable it to carry on positioning. The performance of the proposed spoofing detection method is evaluated through a real-world visual/inertial/GNSS dataset and a real GNSS spoofing attack experiment. The results indicate that the proposed method works well even when the deviation caused by spoofing is small, which proves the efficiency of the method.

An efficient positioning solution in urban canyons using enhanced extended Kalman particle filter

Sensor Review ◽  
2019 ◽  
Vol 39 (3) ◽  
pp. 407-416
Author(s):  
Qimin Xu ◽  
Rong Jiang
Keyword(s):  
Particle Filter ◽  
Inertial Sensor ◽  
Global Navigation Satellite Systems ◽  
Fusion Algorithm ◽  
Content Type ◽  
Satellite Systems ◽  
Tightly Coupled ◽  
Reduced Inertial Sensor System ◽  
Particle Filter Algorithm ◽  
Global Navigation Satellite

Purpose This paper aims to propose a 3D-map aided tightly coupled positioning solution for land vehicles to reduce the errors caused by non-line-of-sight (NLOS) and multipath interference in urban canyons. Design/methodology/approach First, a simple but efficient 3D-map is created by adding the building height information to the existing 2D-map. Then, through a designed effective satellite selection method, the distinct NLOS pseudo-range measurements can be excluded. Further, an enhanced extended Kalman particle filter algorithm is proposed to fuse the information from dual-constellation Global Navigation Satellite Systems and reduced inertial sensor system. The dependable degree of each selected satellite is adjusted through fuzzy logic to further mitigate the effect of misjudged LOS and multipath. Findings The proposed solution can improve positioning accuracy in urban canyons. The experimental results evaluate the effectiveness of the proposed solution and indicate that the proposed solution outperforms all the compared counterparts. Originality/value The effect of NLOS and multipath is addressed from both the observation level and fusion level. To the authors’ knowledge, mitigating the effect of misjudged LOS and multipath in the fusion algorithm of tightly coupled integration is seldom considered in existing literature.

scholarly journals Drones and global navigation satellite systems: current evidence from polar scientists

2020 ◽  
Vol 7 (3) ◽  
pp. 191494 ◽  
Author(s):  
Iain Sheridan
Keyword(s):  
Strong Relationship ◽  
Specific Pattern ◽  
Unmanned Vehicles ◽  
Global Navigation Satellite Systems ◽  
The Arctic ◽  
Current Evidence ◽  
Navigation Satellite ◽  
Satellite Systems ◽  
Global Navigation ◽  
Global Navigation Satellite

Aerial unmanned vehicles, so-called drones, present a paradigm shift away from the long-term use by scientists of manned aeroplanes and helicopters. This is evident from the number of research articles that focus on data obtained with drones. This article examines the use of aerial drones for scientific research in cryospheric regions, especially Antarctica and the Arctic. Specifically, it aims to provide insights into the choices and performance of global navigation satellite systems (GNSS) use for drones, including augmentation systems. Data on drone GNSS navigation and positioning in the context of scientific polar research have been scarce. Drone survey data obtained from polar scientists in April 2019 is the first representative sample from this close-knit global community across the specialisms of climatology, ecology, geology, geomorphology, geophysics and oceanography. The survey results derived from 16 countries revealed that 14.71% of scientists used GALILEO, 27.94% used GLONASS and 45.59% used GPS. Many used a combination of two or more GNSS. Multiple regression analysis showed that there is no strong relationship between a specific pattern of GNSS augmentation and greater positioning accuracy. Further polar drone studies should assess the effects of phase scintillation on all GNSS, therefore BEIDOU, GALILEO, GLONASS and GPS.

Investigation of Alternative Parameters for Immunity-based UAV Navigation in GNSS-denied Environment

2020 ◽  
Vol 09 (01) ◽  
pp. 65-72
Author(s):  
Mohanad Alnuaimi ◽  
Mario G. Perhinschi
Keyword(s):  
Autonomous Navigation ◽  
Dead Reckoning ◽  
Global Navigation Satellite Systems ◽  
External Information ◽  
Artificial Immune ◽  
Tracking Errors ◽  
Satellite Systems ◽  
Vehicle Position ◽  
Global Navigation Satellite ◽  
Uav Navigation

This paper is focused on analyzing effects of several significant parameters on the performance of an immunity-inspired methodology for autonomous navigation of unmanned air vehicles when measurements from global navigation satellite systems (GNSS) or similar current sources, including external information of opportunity, are not available. An artificial immune system (AIS) provides corrections to a dead reckoning algorithm for adequate estimates of vehicle position and velocity. Parameter effects are assessed and analyzed through simulation in terms of trajectory tracking errors during autonomous flight.

scholarly journals Problems of creating autonomous navigation systems on geophysical fields

2021 ◽  
Vol 310 ◽  
pp. 03008
Author(s):  
Vyacheslav Fateev ◽  
Dmitrii Bobrov ◽  
Murat Murzabekov ◽  
Ruslan Davlatov
Keyword(s):  
Autonomous Navigation ◽  
Global Navigation Satellite Systems ◽  
Navigation Systems ◽  
Integrated Navigation ◽  
Geophysical Fields ◽  
Satellite Systems ◽  
Integrated Navigation System ◽  
New Methods ◽  
The Stability ◽  
Global Navigation Satellite

Global navigation satellite systems, which provide high accuracy of navigation, in certain conditions (in tunnels, in closed rooms, in conditions of interference, etc.) have restrictions on their use. In this regard, in order to ensure “seamless” navigation in any conditions of the situation, it becomes necessary to develop new methods and means to increase the stability of navigation definitions. The article is devoted to the consideration of the problems of creating an integrated navigation system using measurements of the parameters of the Earth’s gravitational and magnetic fields. Requirements for meters of parameters of geophysical fields and navigation charts are considered, a number of new navigation meters, new methods and means of preparing navigation charts are proposed. The ways of development of relativistic geodesy and the possibility of using the achievements of gravitational-wave astronomy in gravimetry are considered.

scholarly journals Accuracy Benchmark of Galileo and EGNOS for Inland Waterways

2020 ◽  
Author(s):  
G Yayla ◽  
S Van Baelen ◽  
G Peeters
Keyword(s):  
Sensor Fusion ◽  
Autonomous Navigation ◽  
Global Navigation Satellite Systems ◽  
Navigation Systems ◽  
Inland Waterways ◽  
Satellite Systems ◽  
Coordinate Measurement ◽  
Measurement Units ◽  
Satellite Navigation Systems ◽  
Global Navigation Satellite

While Global Navigation Satellite Systems (GNSS) serve as a fundamental positioning technology for autonomous ships in Inland Waterways (IWW), in order to compensate for unexpected signal outages from constellations due to structures such as bridges and high buildings, it is not uncommon to use a sensor fusion setup with GNSS and Inertial Measurement Units (IMU)/Inertial Navigation Systems (INS). However, the accuracy of this fusion relies on the accuracy of the main localization technology itself. In Europe, Galileo and the European Geostationary Navigation Overlay Service (EGNOS) are two satellite navigation systems under civil control and they provide European users with independent access to a reliable positioning satellite signal, claiming better accuracy than what is offered by other accessible systems. Therefore, considering the potential utilization of these systems for autonomous navigation, in this paper, we discuss the results of a case study for benchmarking the accuracy of Galileo and EGNOS in IWW. We used a Coordinate Measurement Machine (CMM) and a sub-cm Real-Time Kinematic (RTK) service which is available in Flanders to quantify the benchmark reference. The results with and without sensor fusion show that Galileo has a better horizontal accuracy profile than standalone Global Positioning System (GPS), and its augmentation with EGNOS is likely to provide European IWW users more accurate positioning levels in the future.

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