The Importance of Human Motion for Simulation Testing of GNSS
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The Importance of Human Motion for Simulation Testing of GNSS Kimon Voutsis, Paul D Groves, University College London, United Kingdom Mark Holbrow, Colin Ford, Spirent Communications plc, United Kingdom BIOGRAPHY ABSTRACT Kimon Voutsis is a PhD student of the Space Geodesy and Human motion is generally considered benign to the Navigation Laboratory (SGNL) at University College performance of global navigation satellite system (GNSS) London (UCL). He is interested in positioning sensors and and other positioning sensors. This study proves that this is navigation systems, human biomechanics and routing not the case, even for typical human behaviour involving models. The aim of his current research is the development GNSS user equipment, e.g. in smartphones. Using of a pedestrian motion model intended for testing the recorded human motion, it is shown that phase-lock loops performance of positioning sensors in a simulation (PLLs) in GNSS receivers are sensitive to jerk dynamics environment. He holds a first-class Bachelor (Hons) in induced by user motion, resulting in carrier cycle slips. Geography from Harokopio University of Athens, Greece and an MSc in Geographic Information Science from UCL. To test the effects of human dynamics on GNSS carrier He has worked for three years in technical analysis and tracking, real human motion profiles were captured. These developing GIS software solutions for the transport profiles comprised typical types of movements using a industry. ([email protected]) mobile phone, e.g. holding, answering and texting, different types of activities, e.g. walking or jogging, as well Dr Paul Groves is a Lecturer (academic faculty member) at as different phone locations on the human body, e.g. in a UCL, where he leads a program of research into robust hand, pocket, backpack and on an arm band. The data were positioning and navigation within SGNL. He joined in captured outdoors using an Xsens MTi-G MEMS (Micro- 2009, after 12 years of navigation systems research at Electronic Mechanical Systems) Inertial Measurement DERA and QinetiQ. He is interested in all aspects of Unit (IMU) aided by a Global Positioning System (GPS) navigation and positioning, including multi-sensor receiver with a 100Hz output rate. Then the captured integrated navigation, improving GNSS performance motion (MoCap) was processed and input into a simulated under challenging reception conditions, and novel PLL in Matlab with different tracking loop bandwidths positioning techniques. He is an author of more than 60 (BL_CA) and carrier power-to-noise density ratios (C/N0). technical publications, including the book Principles of GNSS, Inertial and Multi-Sensor Integrated Navigation The results show that pedestrian gestures and type of Systems, now in its second edition. He is a Fellow of the activity, e.g. walking or jogging, affect the performance of Royal Institute of Navigation and holds a bachelor’s degree the simulated PLL more adversely than the location of the and doctorate in physics from the University of Oxford. phone on the human body. Also, to track pedestrian motion encompassing these gestures, activities and receiver Mark Holbrow has worked with Spirent Communications locations, a minimum of 15Hz tracking bandwidth is (formerly STC, Nortel and Global Simulation Systems) for required. Consequently, receiver manufacturers should 20 years. Key responsibilities throughout that period have exercise caution before reducing tracking bandwidths to been in the design and development, and now the compensate for the reduction in C/N0 resulting from GNSS management and direction, of Spirent’s extensive range of antenna design, human body masking and the effects of GNSS RF Simulation and Inertial Test Systems. He holds buildings, trees and other environmental features. an MEng in Communications, Information and Electronic Engineering from University Of Plymouth, Devon, This paper also proposes and describes a pedestrian motion England. model (PMM) that simulates the GNSS antenna trajectory in 3D, when it is held by or attached to a pedestrian. The Colin Ford is Staff Software Engineer at Spirent PMM will be validated using real MoCap scenarios and Communications plc. will enable Spirent to increase their product offering in the area of simulation-based testing of positioning sensors for pedestrian applications by generating human motion profiles which affect realistically the performance of GNSS user equipment. !"#$% $#&'(! !" 1. INTRODUCTION the present study and Section 6 discusses the future work which will be carried out to complete the project. Providing a truth reference model is key to testing positioning devices’ performance both in field trials and 2. BACKGROUND simulation environments, especially for pedestrian applications where the great variability of human motion This Section outlines the underlying thematic areas of this induces additional challenges. Human activities and the study, namely human motion capture and modelling, as context where they take place, involve many different well as carrier tracking loops in GNSS receivers. These types of motion, e.g. walking, running, side-stepping, topics encompass the concepts and tools that will help to ascending/descending stairs etc., and encompass particular address the problem statement of this paper, i.e. how motion quantities, such as position, attitude, linear or human motion can affect the performance of GNSS angular velocity, acceleration and jerk (acceleration rate of receivers in terms of inducing artificial cycle slips in carrier change). These specific motion characteristics in turn may, phase-tracking loops. or may not, have an impact on GNSS sensors’ performance, e.g. those inside smartphones, by inducing 2.1 Human motion: capture and modelling phase cycle-slips and false frequency locks in the carrier phase and frequency tracking functions of the GNSS Human motion can be captured by a range of different receiver [1][2][3]. Therefore, to design a truth reference sensors or their combinations. For clinical applications, model for testing positioning devices for pedestrians, it is optoelectronic systems using active or passive markers are essential to study the motion characteristics of human standard [4], or IMUs, which typically encompass a triad motion within a given context and how it affects the of accelerometers and gyros. IMUs are self-sufficient performance of GNSS receivers. This study will support devices in terms of providing a position and attitude the development of an application where a user can drive a solution without the need of any other external sources of PMM to recreate realistically the effects of human motion information, e.g. radio signals. IMUs’ range of applications on GNSS receivers. spans from everyday use, e.g. inside car navigation systems or smartphones, to special military applications, e.g. Human motion is generally considered benign to the ballistic missiles. In [5], the authors assess how suitable performance of GNSS and other positioning sensors. This inertial sensors are for the study and analysis of human study proves that this is not the case, even for ‘day-to-day’ motion, concluding that they have the potential to be pedestrian behaviour involving GNSS user equipment. employed in clinical applications involving walking. Due Using recorded human motion, it is shown that phase-lock to the wide range of applications that employ IMUs (as part loops (PLLs) in GNSS receivers are sensitive to jerk of Inertial Navigation Systems) with different performance dynamics induced by human motion, resulting in carrier requirements, IMU performance grades may be cycle slips. The receiver performance for pedestrian categorised into consumer or automotive, tactical, navigation therefore depends on where the antenna is intermediate, aviation, and marine grades, as detailed in placed and the type of activity, e.g. walking or jogging. [1]. According to this categorisation, the Xsens MTi-G Human motion is also subject to great variability IMU used in this study, is on the boundary between depending on individual characteristics, e.g. gender, health consumer and tactical grades, although there is no uniform status [2]. Therefore, appropriate modelling of human definition of these categories among authors. motion is critical for testing its effects on GNSS receivers. This study proposes a method of modelling human motion, An essential part of using IMU sensors for human MoCap using a human biomechanical model (HBM), also called is the static bias calibration of the constituent inertial “humanoid”, “anthropoid”, or “human skeleton” by other sensors. The Xsens MTi-G IMU/GPS allows calibration of authors, which will be driven by a pedestrian routing model the static bias of the accelerometers, by performing (PRM) in order to simulate the 3D trajectory of a GNSS manoeuvres prior starting the MoCap. A typical pre- antenna, held by or attached to a pedestrian. The output of calibrated MEMS IMU, such as the Xsens MTi-G, is the proposed PMM will be compared in the future with subjected to 0.02 m/s2 accelerometer static bias (1σ) and 1 human MoCap data to ensure that both have the same effect deg/s gyro static bias (1σ) [6]. on GNSS carrier tracking loops. Another important aspect of human MoCap, using an This paper is organised as follows. Section 2 introduces IMU/GNSS device, is the GNSS antenna location on the briefly the state of the art in the areas of human motion human body. Ideally, the selected sensor locations, should capture