If you rely heavily on GPS, your confidence is likely to be misplaced - and that's just to find a friend's house, restaurant, or the trendiest bar.
Experts are beginning to study the resilience of global Positioning System (GPS) satellite navigation networks to the effects of intentional or unintentional electronic interference. The emerging response has not been very good.
RF and microwave experts at Spirent Communications plc in Crawley, UK, have been studying electronic interference in GPS signals for a year and have come to some surprising conclusions.
"We searched the globe for GPS interference and found many incidents of interference - some intentional," said Guy Buensel, a PNT technical specialist at Spirent, a multinational telecommunications test and measurement company.
If the reliability of in-vehicle GPS systems is questionable, what are the implications for commercial air traffic control, radar systems, intelligent munition guidance, or fleet management of trucks and cargo ships?
After a year of GPS testing, Spiellen's findings include: Satellite navigation signals are subject to a variety of disturbances that can damage, degrade or eliminate GPS signals during a one-time temporary event.
These temporary GPS outages can cause more problems than we see. The reason for this is that ground-based GPS users rely heavily on the service both for timing and location information. GPS satellites have precise atomic clocks that can provide unprecedented precision timing.
"We've seen examples of broadcast systems or telecommunications systems that could be out of sync," Buensel said. "In digital broadcasting, that means you can lose entire segments of a show."
In another incident measured at Logan Airport in Boston, Massachusetts, the airport's airborne ground approach system recorded a temporary anomaly caused by a simple electronic signal jammers driven by a cigarette lighter in a vehicle.
These small GPS jammers sell for less than $50, and by creating a quarter-mile-wide RF jamming bubble around the vehicle, users can frustrate efforts to track the vehicle using GPS signals. The problem arises when the car passes through airports or other facilities that rely on GPS positioning and timing.
"GPS signals are weak and susceptible to interference," notes Buensel. "We have been monitoring L1 GPS interference since May 2015. We put receivers on rooftops in the UK. I thought we were lucky to see interference. In one month, we registered hundreds of cases of interference. All around us are stations with lots of electrical switches. There's a lot of accidental interference, but we've seen some cases of intentional interference. "
Can intentional and unintentional GPS interference cause planes to crash or trucks to crash into buildings? That's unlikely because most GPS devices that are critical to missions and lives have enough backups to handle intermittent outages, Buensel said.
Spirent experts are working to raise awareness of the potential interference of GPS devices to help users prepare for the inevitable. If users know they are vulnerable to interference, they can take steps to mitigate its effects.
"GPS interference depends a lot on line of sight," Buensel said. "It would be useful to know there's GPS interference nearby so you can move the antenna." Other solutions may involve maintenance systems like oscillators or complementary systems like Roland, "he said.
Military system designers can often use techniques such as beam control or antenna elimination to counter attempts to jam GPS signals. "There are multiple solutions, depending on what you want to do and pinpoint the value to you," Buensel said.
