Inside Unmanned Systems provides actionable business intelligence to decision-makers and influencers operating within the global UAS community. Features include analysis of key technologies, policy/regulatory developments and new product design.
Issue link: http://insideunmanned.epubxp.com/i/741945
Q+A 70 unmanned systems inside October/November 2016 Q G F Q: Are unmanned aircraft at greater risk from GPS jamming and spoofi ng? a: The potential for jamming would be heightened any time you're up in the air because of the line of sight. If you're at ground level…there's a good chance a building or a bush or a tree or another car gets in the way. But if you're up above, there's a pretty good chance that you're going to be seeing that truck jammer 100 percent of the time. …(Spoofing's) pretty unlikely because it requires a lot of technical sophistication to do that. LOGAN SCOTT HAS MORE THAN 35 YEARS of military and civil GPS systems engineering experience. A consultant specializing in radio frequency signal processing and waveform design, he pioneered approaches for building high-performance, jamming-resistant digital receivers. He is a cofounder of Texas-based Lonestar Aerospace and holds 39 U.S. patents. Q: Is GPS interference more of a problem than it used to be? a: It's a growing problem and the reason it's a growing problem is there's a lot more motivation now because we have a lot of tracking devices out there. You've got the obvious fleet management ones where employers are trying to know where their vehicles are and perhaps employees don't want their employer to know where they are. Car theft is a motivation. …If you are going to steal a car now there's a good chance it's going to have a tracker on it. So, if you don't want to get caught right away, GPS jamming is a possible way to do that. Then, finally, a lot of cargo containers and trucks have GPS onboard for tracking purposes, anti-hijacking and whatnot—again a motivation for jamming. Q: If your GPS signal were interfered with, what typically would happen? a: You would not be able to do the au- tonomous navigation. In other words, if you set up a series of waypoints and you suddenly don't know where you are precise- ly, and you don't have a way to determine that —you get lost. …And then things like altitude hold—if you set an altitude at say 200 feet above the ground and the GPS is lost, you might have to rely on the barom- eter and that may not work very well. I would argue that ( jamming) would impact platform stabilization. Q: Can your GPS receiver be good enough to get you where you need to go but suffer enough interference that it impacts, say, a surveying job? a: Yes. …As an example if I'm just sort of flying along, and I get occasional glitches in the GPS because of jamming, that is not going to be a big deal if I'm just trying to get from point A to point B. But if I'm trying to do a laser survey on everything I see as I go from point A to point B, then the glitches are basically going to create data outages. Q: How can you tell if a problem is because of GPS interference? a: Receivers need to be a little bit smart- er. It's pretty easy to detect jamming, and spoofing as well—but you have to be looking for it and a lot of receivers don't look for it now. …At the receiver level there're lots of things that can be clues. If you see an elevated power level coming in precorrela- tion, that's a good indication of jamming or interference of some sort coming in. …So the short answer to your question is: a well- designed, smart receiver will recognize that it is being interfered with and will alert the user to that fact. Five Good Questions LOGAN SCOTT