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Blog Editor’s Note: In the context of this journal “ITS” stands for “Intelligent Transportation Systems.”
Resilient wireless navigation and time are key for improved transportation systems, whether it is traffic flow, signal coordination, or increasingly autonomous vehicles. Even the best wheel counters, Lidar, and map systems need to initialize, and all networks and IT systems need a common time source for synchronization.
The article makes a good point asking why transportation officials and technologists aren’t more concerned about GPS/ GNSS vulnerability.
Many of our readers will find some of the technical information about relative signal strengths and jammer effectiveness interesting also.
Why GPS may get into a jam
We all rely on GPS these days – and the technology is prevalent in ITS. But it’s potentially vulnerable so why aren’t we more worried about GPS being jammed, asks Steve Petrie
Since fully opening to civilian use in 2000, the Global Positioning System (GPS) has woven itself pervasively into our lives. On land, water and in the air. Location, navigation, tracking, mapping, timing. In vehicles, phones, watches. Turn-by-turn navigation, transit bus times, mining, surveying…
GPS beams to Earth from 24 main satellites orbiting 20,000 km away, radio-frequency (RF) messages identifying the satellite and giving its position and the time.
A GPS receiver tunes to four satellites, computing the distance to each based on the time a message takes to arrive and the speed of light. Then the receiver computes its three-dimensional location in relation to the four satellites, and in relation to the earth.
The table below shows three low-power RF signals: cell phone, GPS and DSRC – a crucial Vehicle to Vehicle (V2V) wireless pr
otocol.
The weaker the RF signal, the more vulnerable that signal is to disruption by random noise injection attack (otherwise known as jamming). The table below starkly illustrates the extreme weakness of GPS signals.
