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RNTF Report

Very few people know how to report problems with GPS reception. And few of those take the trouble to do it. So the listing that the US government maintains of GPS disruption reports really represents the tip of the iceberg. Likely only the most sophisticated and diligent users, often with the most persnickety problems, appear on the website.

We like to check in on the listing periodically and see what kinds of things have shown up. The reports so far in 2020 have been a varied collection.

There are always a number of problems that the government says are due to “user equipment.” Interestingly, problems due to week rollover are still being reported, along with the usual number of receivers that needed updating or had another sort of problem.

In February and July of this year there were problems with the GPS ground control system that caused the information broadcast to contain minor errors. These was detected and reported by some sophisticated users and acknowledged by the Air Force’s GPS Operations Center. The web page, which goes back as far as 2017, shows similar events in February and November of 2018, and in May of 2017.

The most interesting by far, though, are the ones the government categorizes as “unknown interference” or “insufficient information.”  Reading the information that is posted, it is not hard to imagine either a sloppy technician allowing their equipment to emit interference, or some sort of malicious actor with a jammer.

The site includes a number of reports from the Mediterranean and Middle East, which are never any surprise. US military commanders have called the area the most contested electronic warfare environment in the world.

A significant number of reports suggest persistent interference due to a device fixed in one place.

  • A persistent problem in Edmonton, Canada, …that has been going on for quite some time.
  • In Lancaster, CA a  ... permanent disruption of GPS reception noticed over 6 months, driving daily in early evening and late evening, and is detected by 2 separate models of Garmin automotive GPS units. There is no overhead signage that could cause a drop out. The drop out and loss of reception covers a span of approximately 200-300 yards centered on the Ave J overpass.
  • Boulder, CO reported …Noticed irregular signal multiple times near the same block during weekdays.
  • From New Hampshire …I have had a number of intermittent GPS issues within 1 mile of this location over the past year. GPS drops almost exactly 10 mph and the location plots diverge for approximately 1km parallel to the actual track. I took a picture of the GPS track showing the deviation. Contact me if you would like a copy of the track picture. I had previous similar incidents in the same vicinity.
  • In Puerto Rico …My GPS position is changing. Beginning on 1-14-2020 almost every day, why is that? I measure from the same point at my home.

There are also quite a few that could well be due to a mobile source, possibly someone with a “personal jammer”:

  • Driving in San Francisco and across the Golden Gate bridge with …a 1,000 foot offset to the west.
  • A US Coast Guard vessel in Atlantic Beach, FL reported ...losing both of the ship’s GPS receivers during their mooring evolution. Unit verified with another USCG vessel, at the pier, who was experiencing the same issue. Unit restarted both GPS displays with no resolve. After waiting approximately 20 minutes GPS signal regained and seems to be working properly.
  • In Warrenville, IL I used GPS for a trip immediately prior to this anomaly, without issue. When I attempted to enter my next trip leg, I noted an anomaly. My GPS apps could not locate my vehicle correctly and could not plot a course to my destination. The map display spun around multiple times, and at times placed my vehicle at the end of nearby dead end roads and even in the middle of a nearby field. I restarted the apps, to no avail. I restarted my phone and the bizarre behavior continued. About fifteen minutes after first noting the problem, I restarted my phone again and my GPS apps began working correctly. I do not know if it was a device issue or a GPS system issue. As of this date, I have used GPS twice on this device, without issue.
  • A user in Medford, OR lost their whole network for a while. We use GPS timing servers across our network within the CONUS. Across our network at approximately the same time, the timing servers went into holdover. As this issue was seen in multiple places, we do not think there were any issues with the hardware or software. We are trying to understand if something impacted the GPS satellite systems ability to provide timing on March 16th, 2020. (there wasn’t)
  • Near Dulles Airport in VA  I was on Rt. 50 heading East near Avion Pkwy close to Dulles Airport. The GPS navigation in my vehicle stopped working. When I looked for more information in the GPS it displayed no bars for a GPS satellite signal. This outage continued until the end of my trip in Reston, VA. I made two attempts to turn off my vehicle and restart the navigation during the trip, but this did not work to restart my GPS navigation. It was when I stopped the vehicle, stopped the engine, and got out of my car for 10-15 minutes that the GPS system resumed activity. 
  • Rehoboth, MA – Position shown on maps was off by approximately .5 mile to the west. Also had same occurrence last night while in the same general area. When I noticed the issue on my Nav radio, I checked location on my iPhone and it was consistent with the radio in showing the wrong location.
  • Gibsonton, FL – I was driving following my GPS when all of sudden it lost GPS signal on the highway. I checked my vehicles GPS also and it could not lock on to me. It finally returned after about 20 mins but something must have knocked it out.

Quite the collection of reports!

If you would like to check them out yourself, feel free to visit the US Coast Guard Navigation Center website at: https://navcen.uscg.gov/?Do=GPSReportStatus

 

Brad P

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