Václav Navrátil

Czech Technical University in Prague

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Josef Krška

Czech Technical University in Prague

F. Vejražka

Czech Technical University in Prague

Marco Leone

Otto-von-Guericke University Magdeburg

Zoltán Koppányi

The Ohio State University

Graeme E. Smith

Johns Hopkins University Applied Physics Laboratory

Charles Toth

The Ohio State University

J. Landon Garry

Johns Hopkins University Applied Physics Laboratory

Dorota A. Grejner‐Brzezinska

The Ohio State University

Andrew O’Brien

Indiana University – Purdue University Indianapolis

Haowei Xu

Massachusetts Institute of Technology

Cooperative Institutions

Czech Technical University in Prague

The Ohio State University

Brno University of Technology

Johns Hopkins University Applied Physics Laboratory

California Institute of Technology

Ohio University

Universidade Federal do Paraná

VSB - Technical University of Ostrava

University of Defence

Technical museum in Brno

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Distributed Nonlinear Least-Squares Solver for Practical Network Determination

NAVIGATION Journal of the Institute of Navigation (2024)

Josef Krška Václav Navrátil

Abstract

An integral step in an ultra-wideband localization network installation is determining the positions of the fixed infrastructure nodes, the anchors. This process is time-consuming and usually requires specialized equipment. Additionally, it is difficult to achieve scalability, as any change or addition in the network requires a redetermination of the affected anchors. One can automate this process by utilizing the distance-measuring capabilities of the network infrastructure and employing a distributed position estimation algorithm, such as the consensus subgradient (CSG) algorithm. Yet, the CSG suffers from scalability issues due to high problem dimensionality and data-sharing bottlenecks in practical applications. Consequently, implementation in embedded devices is difficult. In this article, we propose a modification of this algorithm, the neighborhood CSG, which aims toward embedded implementation by local reduction of the problem dimensions without hindering the precision of the original CSG algorithm or its convergence rate.

Solver

Least-squares function approximation

10.33012/navi.658

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Citations (0)

GEOREFERENCING IN GNSS-CHALLENGED ENVIRONMENT: INTEGRATING UWB AND IMU TECHNOLOGIES

The international archives of the photogrammetry, remote sensing and spatial information sciences/International archives of the photogrammetry, remote sensing and spatial information sciences (2017)

Charles Toth Zoltán Koppányi Václav Navrátil Dorota A. Grejner‐Brzezinska

Abstract. Acquiring geospatial data in GNSS compromised environments remains a problem in mapping and positioning in general. Urban canyons, heavily vegetated areas, indoor environments represent different levels of GNSS signal availability from weak to no signal reception. Even outdoors, with multiple GNSS systems, with an ever-increasing number of satellites, there are many situations with limited or no access to GNSS signals. Independent navigation sensors, such as IMU can provide high-data rate information but their initial accuracy degrades quickly, as the measurement data drift over time unless positioning fixes are provided from another source. At The Ohio State University’s Satellite Positioning and Inertial Navigation (SPIN) Laboratory, as one feasible solution, Ultra- Wideband (UWB) radio units are used to aid positioning and navigating in GNSS compromised environments, including indoor and outdoor scenarios. Here we report about experiences obtained with georeferencing a pushcart based sensor system under canopied areas. The positioning system is based on UWB and IMU sensor integration, and provides sensor platform orientation for an electromagnetic inference (EMI) sensor. Performance evaluation results are provided for various test scenarios, confirming acceptable results for applications where high accuracy is not required.

GNSS augmentation

10.5194/isprs-archives-xlii-1-w1-175-2017

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Citations (2)

Comparing the steady-state procedures based on epsilon-algorithm and sensitivity analysis

Josef Dobeš David Černý F. Vejražka Václav Navrátil

Although many programs have built-in various methods for finding the steady state nowadays, their actual implementations are often quite unsatisfactory regarding algorithm efficiency and reliability. We improved and checked procedures built on both e-algorithm and sensitivity analysis in time domain. First of all, it was clearly demonstrated that increasing demands on the overall numerical accuracy do not lead to an excessive number of necessary integration steps and therefore LU factorizations correspondingly. This feature is especially significant for the suggested procedure based on the e-algorithm. Furthermore, the practical experiments confirmed that a proposed arrangement of the extrapolation method is greatly insensitive to its order, which is even more important because a program user is unable to estimate the appropriate order for complicated circuits well. The properties of the methods are demonstrated using rectifier, C-class amplifier, and LNA for which exceptional attention was given to checking the insensitivity of the extrapolation to its order.

Feature (linguistics)

Implementation

10.1109/icecs.2015.7440388

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Citations (2)

Analysis of the Common-Mode Radiation from Differential Signalling on Printed Circuit Boards

Marco Leone Václav Navrátil

Common-mode signal

Mode (computer interface)

10.23919/emc.2003.10806268

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Position estimate using radio signals from terrestrial sources

Václav Navrátil Rostislav Karásek F. Vejražka

The satellite navigation is supposed to be used in applications that need coordinates generally. However we can meet a plenty of satellite signal reception problems in a real environment, often called as difficult conditions. The difficult conditions hinder reliable positioning with required accuracy, often in applications that are important for saving or securing the safety of human lives (work of rescue teams, protection of people in large warehouses, safety of lone forest workers, etc.). The main reason for this is the weakness of the received satellite signals. In addition to that, the weak signals are also highly vulnerable by interference, spoofing or jamming, even with the low-power and often generated by low-cost devices. In spite of this, radio systems complementing and making the backup of the satellite positioning are searched. There are terrestrial radio systems using high-power signals with properties which are suitable for the positioning purposes. The most important property in conjunction with the sufficiently high power is a very sharp and possibly unambiguous correlation function. Besides the signals of systems used primarily for the navigation (such as eLORAN, e.g.) signals of some systems primarily dedicated to communication have the acceptable properties mentioned above. They are usually called Signals of Opportunity. As an example let us mention signals of the DVB-T, LTE, Wi-Fi, etc. In the field of indoor navigation signal strength fingerprinting is frequently used. However, for much larger open areas this approach is not the best one, because it requires a kind of a site survey to be done. In case of outdoor applications, the use of different principles has to be considered. The methods based on signal power and angles of arrival measurements have been found unsuitable because they may be misleading even in a lightly obstructed area. Range estimation using packet round trip delay (similar concept to the DME ranging used in aviation) is not possible because most of the systems do not have a stable response delay. However, some systems with synchronous transmitters (or base stations) can be used by the way of hyperbolic navigation concept. Luckily many of the systems with high transmitted power, such as TV broadcast or cellular data systems downlink have the precise transmission timing incorporated. This contribution describes utilizing the OFDM Signal of Opportunity for the positioning purposes. The proposed method is based on the peak search in an estimated radio communication channel model. The time differences of arrivals of signals from individual transmitter pairs can be measured in this way. At least two independent measurements must be used for the final two-dimensional position estimate by the iterative LevenbergMarquardt algorithm. With three independent measurements the 3D positioning is available. Because the measured differences do not have generally to share the common timescale (only the measurement pairs have to), combining of more independent systems together is possible by nature of our approach. The validity of the above mentioned theoretical concept is demonstrated and verified by means of an experiment on real captured DVB-T (OFDM modulated) signals. Moreover, an analysis of transmitter geometry influence on the positioning accuracy is also shown and the graphical output for the real scenario is provided. Considering these results, future goals and improvement possibilities are formulated.

Spoofing attack

SIGNAL (programming language)

10.1109/plans.2016.7479775

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Chained wireless synchronization algorithm for UWB-TDOA positioning

Václav Navrátil Josef Krška F. Vejražka V. Korecek

The Time Difference of Arrival is a popular method for UWB-based positioning, since it allows high position update rate even for multiple users. However, it requires the network infrastructure (anchors) to be synchronized, preferably with sub-nanosecond accuracy. Herein, an approach for synchronizing multiple anchors in a wireless, line-of-sight manner is described. This method is able to deal with UWB modules equipped with inexpensive drift-prone oscillators, as such impairments are estimated and compensated. By applying the proposed approach the influence of generally variable environment (e.g. temperature) on timing and positioning performance is reduced. Moreover, the presented algorithm is suitable for straightforward chaining of the line-of sight-segments in order to allow synchronization of distant anchors that cannot be synchronized with the master anchor directly.

Synchronizing

Chaining

Position (finance)

Line (geometry)

10.1109/plans.2018.8373376

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Citations (8)