GNSS 101: An Introduction

Time: Monday, September 16, 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.

Introduction to Space Weather

Time: Monday, September 16, 1:30 p.m. - 3:00 p.m.

Space Weather is an emerging field of space science that studies how the Sun influences the Earth’s space environment, and the impacts of those interactions on technological and society. Some of the most intense interactions can damage our Earth-orbiting commercial and scientific satellites; threaten astronaut safety; introduce high levels of radiation for crews and passengers in flights crossing over the poles; disrupt electric power grids, oil pipelines and the reliability and accuracy of global communications and navigation systems, including GNSS. With society’s ever-increasing dependence on space-based technology it is important to be aware of Space Weather, its potential impacts and what governments are doing to enhance forecasting and mitigation of its most damaging effects.

This course will introduce the basic physical concepts of the source of Space Weather. This includes information on the Sun, solar wind, eruptive solar phenomena, magnetosphere, ionosphere and geomagnetic induction. The course will continue with a view of the impacts of Space Weather on technological systems in space and on the ground. Finally, we will introduce current government policy and plans to enhance forecasting capabilities and mitigation of Space Weather.

Patricia H. Doherty is the director and a senior scientist of the Institute for Scientific Research at Boston College where she leads studies of space physics, space weather, ionospheric and atmospheric effects on space-based systems, and ionospheric measurement techniques. She is an ION Fellow; recipient of the ION’s Burka, Weems and Distinguished Service Awards; recipient of the GPS World Leadership Award; and a past ION president.

Sensor Integration for Personal Navigation

Time: Monday, September 16, 1:30 p.m. - 3:00 p.m.

A review of the state-of-the-art navigation sensors and techniques suitable for personal and pedestrian navigation, with an extension to the Unmanned Aerial Systems (UAS) navigation. Personal Navigation (PN) is defined as navigation for military and emergency personnel, while pedestrian navigation refers to location/navigation/tracking of all other types of mobile users. An emphasis will be on navigation sensors and techniques in GNSS-challenged environments, such as inertial measurement unit (IMU), wireless local area network, IR and RF transponders, and ultra-wideband (UWB) networks, as well as 2D and 3D active and passive imaging sensors. Following the technology overview, sample implementations and performance assessment of selected navigation system prototypes will be presented. System design, as well as a summary of the performance analysis in the mixed indoor-outdoor environments, with special emphasis on dead-reckoning (DR) performance, will be discussed.

Dr. Dorota A. Grejner-Brzezinska is the Lowber B. Strange Endowed Chair and the associate dean for research in the College of Engineering at The Ohio State University (OSU) and a director of the Satellite Positioning and Inertial Navigation (SPIN) Laboratory. Her research interests cover GPS/GNSS algorithms, GPS/inertial and other sensor integration for navigation in GPS-challenged environments, sensors and algorithms for indoor and personal navigation, and mobile mapping. She is a Fellow of the ION, RIN and IAG; recipient of the ION’s Kepler and Thurlow awards; a past ION president; and a member of the National Academy of Engineering.

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

Time: Monday, September 16, 3:30 p.m. - 5:00 p.m.

If you enjoyed the “Measurements from Phones” class last year - come back! We have a whole new set of data and tools for you. 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.

Approaches for Resilient and Robust Positioning, Navigation and Timing (PNT)

Time: Monday, September 16, 3:30 p.m. - 5:00 p.m.

Diverse elements of international infrastructure are critically reliant on GNSS for precise location and time, often in ways that are not obvious. This tutorial provides a high-level perspective on the effects of interference on GNSS receivers and offers some possible threat mitigation approaches and policy recommendations. The tutorial starts with a discussion of potential GNSS threats and vulnerabilities. Then, after a quick review of how receivers determine position, the focus is on the effects of various interference types on select signals. The effects of ground mobile propagation in limiting effective jammer range are examined. Mitigations, such as adaptive arrays and IMU aiding, are discussed. Civil jamming examples and incidents are covered, along with methods to detect, identify and militate against their effects. In particular, the importance of maintaining situational awareness for establishing environmental context is examined. Techniques for detecting civil spoofing and authenticating signals will be discussed.

Logan Scott has over 40 years of military and civil GPS systems engineering experience. He specializes in radio frequency signal processing and waveform design. He has pioneered approaches for building jamming-resistant digital receivers and has long advocated for hardening civil infrastructure. Logan is an ION Fellow and holds 42 patents.

Using a Sextant: Celestial Navigation

Time: Monday, September 16, 3:30 p.m. - 5:00 p.m.

How do modern navigators use a sextant, chronometer, stars, and almanac information to solve for ship or aircraft position? The fundamentals are likely more straightforward than you realize! Today’s mariner typically uses six tools to solve for vessel position:

1. An almanac (or computer) that predicts precise location of celestial bodies as a function of time;
2. A reasonably accurate timepiece;
3. A device to measure elevation angle of a celestial body (e.g., sextant);
4. A “star finder”;
5. A navigational chart; and
6. A mathematical or tabular method to convert observations to contours (lines) of position.

This short course will cover some theory; however, the primary focus will be on the practice of using these six tools to solve for vessel position. Final discussions will focus on experiences with celestial navigation, with topics to include best times to shoot stars, horizon challenges, sources of error, and typical accuracy.

Dr. Richard J. Hartnett is a professor of Electrical Engineering at the U.S. Coast Guard Academy in New London, CT, having retired in 2009 from the USCG as a Captain (O-6). His current research interests include the mathematics of positioning, statistical signal processing methods in electronic navigation, and autonomous vehicle design.