Global Navigation Satellite Systems Engineering, Policy, and Design
A decade has passed since the first GNSS system-level authentication protocols were proposed, and yet the current ongoing discussion is still, “Do we really need GNSS signal authentication?” Indeed, the current argument is whether we need authentication at the system level (the satellite broadcast service) or whether user-based authentication (anti-spoofing) is sufficient for a number of application requirements.
By Inside GNSS
No reality show contestant ever neared the finish line without the producers serving up another challenge. And so it is for would-be multi-GNSS users in the United States.
After dodging budget cuts, thwarting other teams’ attempts to grab critical frequencies, and dealing with jamming and technical problems, members of the U.S. GNSS community were thrown another curve late last year when they learned that signals from GLONASS and other international constellations must be authorized for use in the United States.
By Dee Ann Divis
It is well known that carrier phase ambiguities are integer values. Intuitively, this is hard to understand with a common counter-argument progressing along these lines: even if the receiver measures the instantaneous phase of the incoming signal (thus removing any fractional cycle component at the receiver end), the phase of the signal at the satellite cannot be guaranteed to be zero, so how can the ambiguity be integer?
In this article we explain why the carrier phase ambiguities are indeed integer.
By Inside GNSS
Running San Francisco Marathon, with daughter, Tanera. Note GPS watch.SIDEBAR: Frank van Diggelen’s Compass Points
“It all traces back to my parents,” says Frank van Diggelen. “My father, Tromp van Diggelen, was a surfer. He taught me to surf and swim, in that order, when I was five. I was racing sailboats before I was 10, and there’s a lot of navigation there. Even when you’re just on a lake, the racing is all about reading the wind, understanding angles of convergence, velocity-made-good, and so on.”
By Inside GNSSEvery so often, anthropologists — and maybe a few mathematicians — have a field day puzzling over the origins of our positional base-10 numeral system.
Oh, not the historical origins themselves, the Hindu-Arabic innovations beginning in the 5th and 6th centuries. That’s all pretty much agreed.
No, I’m referring to the possible physiological inspirations, the readily visible digits at the ends of our limbs: 10 fingers, 10 toes.
Coincidence? Does nature have coincidents, or does it abhor them like vacuums — o horror vacui?
By Inside GNSS
Efficient power transmission and distribution would benefit from synchronized near–real-time measurements of voltage and current phasors at widely dispersed locations in an electric power grid. Such measurements also could enable effective real-time system monitoring and control, which are considered to be the key to preventing wide-scale cascading outages like the 2003 Northeast Blackout.
By Inside GNSS
As a navigation satellite transmits multiple signals on single frequency (e.g., Open Service and Restricted Service over L5 Band), these are combined on a common carrier to comprise a composite signal. This composite signal passes through navigation payload subsystems such as an up-converter, traveling wave tube amplifier (TWTA), filters, and so on. These subsystems may introduce adverse effects on the signal, such as amplitude and phase distortion, nonlinear effects, gain imbalance, IQ imbalance, and phase noise.
By Inside GNSS
Figure 2: Sky plot showing position of IRNSS and GPS satellites over Helsinki Finland on November 6, 2014 at 16:10 local time.The Indian Regional Navigation Satellite System (IRNSS)] is designed as a stand-alone regional navigation system with a primary service area extending up to 1,500 kilometers from the Indian land mass. Finland lies north of 60°N latitude more than 5,000 kilometers away from India, as shown in Figure 1 (see photo at the top of this article).
By Inside GNSS
GPS Space Service Volume (SSV) Requirements/Performance ParametersNew space missions such as the robotic repair and recovery of damaged or errant communication satellites may become possible with the aid of an emerging class of receivers that is able to use GPS signals for navigation in orbits thousands of kilometers above the middle Earth orbit (MEO) GPS constellation itself.
By Dee Ann Divis
Russia’s involvement in the Ukraine crisis has turned much of public opinion in the West against that country, in particular souring the relationship between the European Union (EU) and Russia. And, while the ceasefire signed in September technically is still in force, the EU-Russia rift is far from smoothed over.
By Peter Gutierrez
Tables 1, 2, 3 & 4Q: What are the actual performances of GNSS positioning using smartphone technology?
A: “Where I am?” is the typical question asked by a person when visiting a new city or unknown place. Knowing one’s own location is generally a basic necessity for people, both in indoors and outdoors.
By Inside GNSS
Working Papers explore the technical and scientific themes that underpin GNSS programs and applications. This regular column is coordinated by Prof. Dr.-Ing. Günter Hein, head of Europe’s Galileo Operations and Evolution.
SIDEBAR: Locating a Distress Beacon Activated in Flight
By Inside GNSS
