n cellular frequencies.
There are systems and algorithms designed to help compensate for distortions due to the ionosphere and troposphere and we’ll touch on these technologies later.
Sometimes, GNSS signals will bounce off reflective objects as they make their way to the antenna. This is known as multipath because the signal may take multiple paths on its way to the antenna. Multipath is a major problem in providing highly accurate positions from GNSS because it is difficult to detect or model.
Signal interference can be unintentional or intentional. Unintentional interference happens when there is other electronic equipment emitting signals near the GNSS antenna. These other signals interfere with the true GNSS signal. This can reduce the clarity of the GNSS signal and even prevent the receiver from being able to find the signal at all.
Intentional interference usually takes the form of spoofing – giving false signals – or jamming. In both cases, your position is unreliable. Spoofing means that a false signal is provided to the receiver. This happens most often in a military scenario where an agent intentionally tries to generate a wrong position. Jamming can occur in military scenarios as well as in civilian life. Even though they are illegal, inexpensive jammers exist and can wash out GNSS signals altogether.
Engineers have developed algorithms to mitigate the effects of interference and multipath. Additional equipment like anti-jamming antennas can protect your signal from interference, whether that interference is malicious or not.
Here’s a snapshot into some of the technologies developed to protect and resolve positioning errors.
Additional infrastructure like precise point positioning, satellite-based augmentation systems, or real-time kinematic systems provide additional data to correct errors on the original satellite signal. Anti-jamming antennas protect your signals from interference. Specialized algorithms have been developed to make GNSS receivers more robust against these error sources. GNSS positioning can be augmented with other external sensors like inertial navigation systems that help provide additional data to supplement an accurate position. We will explore these technologies in more detail in episode four of our series.
Thanks for joining me for episode two of our introduction to GNSS webinar series! We’ve explored the factors that can affect satellite signals and result in positioning errors and we’ve introduced the technologies that can mitigate them. Our next video examines what happens to the satellite signal once it reaches the receiver. We’ll share some of the calculations used to compute an accurate position. But, if you’re ready to get a head start in learning these GNSS concepts, download our in-depth book An Introduction to GNSS.
Episode three of our on-demand webinar series features Hexagon | NovAtel Technical Marketing Specialist Paul Verlaine Gakne explaining how satellite signals are received and processed to output a position. We include a transcript below.
Hello, and welcome to episode three of Hexagon NovAtel’s webinar series on An Introduction to GNSS. My name is Paul Verlaine Gakne; I’m the technical marketing specialist at Hexagon’s Autonomy and Positioning division. Thanks for joining me!
Today, we’ll illustrate the components of a satellite’s signal, how it’s received by antennas, and what happens when the signal is processed by receivers. We’re scratching the surface, so if you’re ready for a deeper look at GNSS concepts, you can download our Introduction to GNSS book.
We’ve explained that satellites transmit signals, but let’s go into more detail. GNSS refers to global navigation satellite systems, which includes four main groups of satellites known as constellations: GPS, GLONASS, Galileo, and Beidou. Each constellation is managed by a different country, and they each have their own idiosyncrasies. To transmit information, satellites use radio frequencies allotted to GNSS, and each constellation broadcasts on at least two frequencies. For example, GPS broadcasts at L1, L2, 