GNSS 101: An Introduction

Time: Monday, September 21, 1:30 p.m. - 3:00 p.m.

An overview of the principles of satellite navigation and the requisite technologies that matured in the second-half of the 20th century leading to the development of Transit, which became operational in 1964, followed by GPS in 1995. The principal technologies required for a Global Navigation Satellite System (GNSS) are stable space platforms in predictable orbits, global coordinate frames, spread spectrum signals and ultra-stable clocks. These technologies made GNSS possible, but it’s the revolution in integrated circuits that led to a receiver chip, which adds about $1 to the cost of a smartphone and can determine, virtually instantaneously, your position within a couple of meters, velocity within 5 cm/s, and time within 50 ns. These innovations have transformed how we move about, transact commerce and fight wars. As a preview to GNSS 102, this class will also introduce L5, group-delay, intersystem biases and the basics of carrier phase.

Dr. Pratap Misra, an ION Fellow and Kepler Award recipient, has been active in the GNSS field for 30 years, starting with a project at MIT Lincoln Laboratory aimed at combining measurements from GPS and GLONASS to improve navigation for civil aviation.

Space Applications of GNSS

Time: Monday, September 21, 1:30 p.m. - 3:00 p.m.

GNSS receivers have become standard equipment for near-earth satellites, providing the onboard position, velocity, and timing information required to support real-time operations. Furthermore, precise GNSS observations from both direct and indirect paths collected onboard these platforms are used to support scientific and commercial purposes including characterization of Earth’s atmosphere, measurement of ocean surface heights, and extraction of time varying features of Earth’s gravity field. New advances in receiver technology and detailed modeling of the environmental influences on GNSS satellites and signals continue to expand the utility of GNSS to ever-finer orbit resolution and higher altitude missions. This short course will present an overview of the many applications of GNSS in space, and describe the unique challenges and requirements for its use in this environment.

Dr. Penina Axelrad is Joseph T. Negler Professor of Aerospace Engineering Sciences at the University of Colorado Boulder. Her research interests include technology and algorithms for GNSS-based position, navigation, and timing, multipath characterization and correction, and remote sensing using GNSS-based reflectometry. She is a past ION president, a Fellow of ION and AIAA, and a member of the National Academy of Engineering.

PNT and the LEO Constellation

Time: Monday, September 21, 1:30 p.m. - 3:00 p.m.

The principles of navigation based on signals from LEO mega constellations, with emphasis on the efficacy of navigation concepts that rely solely on carrier Doppler shift or beat carrier phase measurements for the downlink communication signals of LEO constellations. Consideration will be given to pseudorange-based concepts, but less emphasis will be put on this type of system. Systems that compute point solutions for position, velocity, clock offset, and clock offset rate using carrier Doppler shift from eight or more satellites will be considered. Also considered will be the needed orbital ephemeris accuracy and clock stability in order for such a system to yield GPS-like accuracy. Additional questions include possible improvements from a filter-based solution that uses beat carrier phase and from the fusion of INS data, magnetometer data, and altimeter data with the LEO constellation’s radio-navigation observables.

Dr. Mark Psiaki is the Kevin Crofton faculty chair in Aerospace & Ocean Engineering at Virginia Tech and is Professor Emeritus of Mechanical & Aerospace Engineering at Cornell. He holds a BA in Physics and a PhD in Mechanical & Aerospace Engineering, both from Princeton University. He is an ION Fellow.

GNSS 102: Measurements from Phones, L1, L5 and Carrier Phase

Time: Monday, September 21, 3:30 p.m. - 5:00 p.m.

Updated in 2019, this course hosts a new set of data and tools. After a brief overview of GNSS raw measurements in phones, we will spend most of the course on the new signals available from smartphones, L5 and Carrier Phase, and the new tools and features available to you (free) including the new release of the Google GNSS Analysis Tools for desktops (see http://g.co/GNSSTools). In this course we will use these tools to analyze: L1 vs L5 sensitivity, L1-L5 group delay, Inter-system biases, and carrier-phase residuals (from which you can see things like phase-drift, and cycle slips). We will also show you custom filters on the raw measurement fields. Example: Do you want to analyze only those signals with C/No > 20 dBHz? Just specify 'Cn0DbHz>20' and the Analysis Tool takes care of it for you. Similarly, for any other Boolean operations on any of the twenty-six fields reported through the raw measurements API.

This class is a follow-on to "GNSS 101 - An Introduction". In GNSS 101 you will be introduced to the fundamentals of GNSS, including L5, group-delay, inter-system biases, and the basics of carrier phase. In GNSS 102, you will learn how to make actual measurements of these values from actual phones.

Dr. Frank van Diggelen is a principal engineer at Google, where he leads high accuracy location development for Android. He is also ION executive vice president and a lecturer at Stanford University, where he teaches GNSS. Previously he worked at Broadcom and Global Locate, developing and implementing Assisted-GNSS, which makes GNSS work in cell phones. He is an ION Thurlow Award and Kepler Award recipient, an ION and RIN Fellow, the author of the textbook "A-GPS", and holds over 90 issued US patents on GNSS. He has a PhD EE from Cambridge University.

Galileo, the European Contribution to the GNSS World

Time: Monday, September 21, 3:30 p.m. - 5:00 p.m.

The class starts with a brief overview of the Galileo system and its architecture, stressing the elements that make Galileo unique versus other satellite navigation systems, with focus on its signal plan and a discussion of its services. Galileo’s novelties that will be discussed include the AltBOC modulation, through which Galileo provides users with the largest bandwidth signal transmitted by any satellite navigation system; and the origins of the MBOC modulation, the signal that is meant to become the new standard of mass-market receivers in the future.

The history of the Galileo Signal plan will be discussed and include technical elements such as the multiplex, modulation, codes, signal correlation properties, power levels but also system aspects on the essential compatibility and interoperability that GNSS systems need to observe. The course will also relate the technical details with the evolution of the Galileo services since their conception, guiding the attendees from the original service plans to the final palette of services that Galileo is providing today.

The class is intended for anyone with an interest in better understanding Galileo signals and services, including researchers, system engineers, application developers, end-users, managers and executives.

Dr. José Ángel Ávila Rodríguez is a GNSS Evolutions Signal and Security principal engineer at the European Space Agency (ESA) where he contributes to laying the foundations of the Galileo signal and security modernization. He also is an enthusiastic educator and co-organizer of the ESA-JRC Summer School. He was recipient of the 2008 ION Bradford W. Parkinson Award, the 2009 ION Per Enge Early Achievement Award, the 2017 European Patent Office Inventor Award in Research category and the 2019 Spanish Cross of the Aeronautical Merit with white Decoration. He is an IEEE Senior Member and an ION Fellow.

PNT for Autonomy

Time: Monday, September 21, 3:30 p.m. - 5:00 p.m.

Automated systems such as self-driving cars, urban air mobility platforms, and communications networks are making unprecedented demands on PNT. They want positioning and timing that is simultaneously decimeter-accurate, extremely reliable despite unusual environmental conditions or intentional interference, and cheap. Can all three desiderata be achieved, or are they mutually irreconcilable, an echo of the business adage "faster, better, cheaper -- pick two!"? This presentation will examine why autonomy makes these demands on PNT and what progress has been made in recent years on each front. The unique PNT challenges of urban air mobility will be highlighted. Various PNT sensing modalities will be assessed in terms of accuracy, reliability, and cost. Recent breakthroughs from the University of Texas Radionavigation Lab in low-cost radar positioning and LEO-satellite-based PNT will be showcased.

Dr. Todd Humphreys is an associate professor at The University of Texas at Austin, where he directs the Radionavigation Laboratory. He specializes in the application of optimal detection and estimation techniques to secure and robust perception for automated systems and centimeter-accurate location. He is an ION Fellow and has received the NSF CAREER Award (2015), the ION Thurlow Award (2015), the Qualcomm Innovation Fellowship (2017), and the PECASE (2019).