I made this site.

Copying a comment I made on HN a few weeks ago:

The ADS-B signals that many aircraft broadcast include not just the aircraft's GPS positions, but also a measure of GPS accuracy (strictly speaking, ADS-B doesn't talk about GPS specifically and can handle any sort of navigation technology; I'm sure there are some planes out there reporting positions based on inertial navigation systems, with correspondingly low accuracy, or GLONASS-derived positions, or whatever, but my understanding is that right now something on the order of 99% of aircraft with ADS-B are using good old GPS so I'll just keep using the term GPS in this description). If you go to https://globe.adsbexchange.com and click on just about any aircraft, you'll see an info sidebar on the left of the screen. Scroll down until you see the ACCURACY section, and you'll see values labeled NACp, SIL, NACv, NICbaro, and Rc. Those are all self-reported measures of the accuracy of the data being sent by the aircraft[1]. NACp is "Navigation Accuracy Category for position", and is a good measure of whether the aircraft's GPS is working well. (A somewhat obscure feature of ADS-B Exchange lets you see a map of all aircraft that are currently reporting poor navigation accuracy for their GPS: https://globe.adsbexchange.com/?badgps)

To make the maps, I process a day's worth of data from ADS-B Exchange to find all the aircraft reporting poor navigation accuracy and then I color map hexes (using H3 hexes) according to the proportion of aircraft passing through that hex that reported bad GPS accuracy. Specifically, I'm counting an aircraft as experiencing "interference" if it at some point reported good navigation accuracy and then reported low accuracy. Doing this helps filter out aircraft that just have an ongoing issue with their GPS equipment, or don't even have GPS.

When I do that, areas where there is systematic interference—almost always jamming by military systems—become obvious. There are a few conflict zones (Syria, Cyprus, Israel) that have been experiencing jamming for years, and the U.S. often has smaller scale military testing, especially in the West and Southwest. You can also see the jammers that are apparently setup around Moscow to prevent drones from flying near Oligarch dachas[2].

I started making these maps in February before Russia invaded Ukraine because I thought it might provide an early warning of an invasion. I didn't see that, and in fact this technique doesn't do a very good job of mapping GPS jamming around the actual war zones because civil aviation stopped over Ukraine, so there are zero or few aircraft with ADS-B reporting their GPS accuracy[3]. Without that data, I can't make a map.

Sometimes I do see changes, like when Russia suddenly started jamming around Kaliningrad in March 2022, causing interference in many Baltic states and leading to Finland to cancel some flights[4]. Then a few days later, they just stopped.

I don't think too many people have realized yet what an amazing source of GPS interference data is available using ADS-B! It's like having thousands of sensors roaming the planet, broadcasting GPS accuracy data every few seconds. I sometimes wonder if I would disrupt someone's nascent business model if I started publishing my maps regularly.

1. https://twitter.com/lemonodor/status/1493789598077440000 2. https://www.gpsworld.com/jammers-at-dachas-add-to-russias-ab... 3. https://twitter.com/lemonodor/status/1497295859196649475 4. https://twitter.com/lemonodor/status/1500719113185816577

A quick update on some of the infrastructure behind the map: One day of being on the front page of HN has used up half of the Mapbox free quota of map loads. To sustain this level of traffic would cost me something like $2000/month just for Mapbox. Since this is a non-profit project that I do in my spare time, something is going to have to give.

This is fascinating. Really cool to see a map of GPS signals on Earth and the site looks really good, too. Love the colors and interface! Awesome :)

Can anyone narrate any of the jammed signals? Like for instance what would be jamming in the ocean between Tripoli and Benghazi? Or what would be jamming around San Antonio, TX?

There was a spot I stood on in Japan probably 20 years ago that made my (handheld Garmin) GPS think I was traveling at something like 700mph at some angle across the globe. Once I left the area by maybe 10 feet, everything returned to normal. Went back to the spot, same thing. Always wondered what caused that.

How difficult is it to build a CRPA receiver? Apparently that’s how the military avoids GPS jamming, and likely why HIMARS is able to remain accurate in the face of Russian jamming (or INS).

Since nobody’s asked: How does GPS jamming work?

Why so much over Cyprus and Turkey?

Thank you for giving us a new way to discover impeding military conflicts. I'm surprised how you have found a way to creatively reuse the existing data.

Awesome map, and awesome use of mapbox.

I haven't followed their progress and was really surprised to see globe view, 3D terrain and custom projections landing in v2.

Cool project, thanks! A bit nitpicking:

> In Europe, Poland, Romania, Lithuania, Latvia, Kaliningrad, and Finland sometimes show presumed jamming activity, depending on how active Russia is.

The wording here is confusing, it seems to imply that Kaliningrad is a country, which it is not (it's a Russian exclave, as the author mentions in one of the HN comments).

Curious, how do you measure your own gps “accuracy”?

Also, is “jamming” a precision reduction (seems improbable given how I think gps works) or a signal strength reduction in this case?

Why is Moscow almost constantly red?

It’s interesting that the only red spot in the US right now is next to Uvalde, TX

Smart use of data in an highly effective visualization. Great.

I know the stories behind some of the regions, or at least some hypotheses.

Interference in the U.S. is almost always the result of military testing or training. If you check against another map (Google maps, or skyvector.com/globe.adsbexchange.com to see sectional charts) you'll see that the interference region is usually centered on or close to a military base or Military Operations Area. There are often FAA notices to pilots about potential GPS outages in those areas.

Around Syria, C4ADS did some research a few years back identifying Russia as the main culprit; I think the conclusion was that Russia is jamming GPS to defend their bases from drone attack. https://www.c4reports.org/aboveusonlystars

At least some of the jamming around Moscow is thought to be an anti-drone measure (to stop nosy photographers? assassins?): https://www.gpsworld.com/jammers-at-dachas-add-to-russias-ab...

In the Baltic, the assumption seems to be that it's usually Russian military.

I wish someone more knowledgeable about what's going on in other regions with interference would write about them! I just don't have the time and expertise do dig into all of them.

> how do you measure your own gps “accuracy”?

Because GPS is way cool. First, there is the official site: https://www.gps.gov/systems/gps/performance/accuracy/ I am far from being an expert, but being a flying nerd, that's what I can tell you:

The more satellites in sight you have access to, the cooler stuff you can do with GPS. Minimum to establish 2D (on globe projection 2D) location is 3 sats, minimum for altitude is 4 sats. There are mathematical simulations you can do to see if, and when, a given aircraft will have access to 4 sats (or more), called RAIM: https://www.mygdc.com/new/static/usermanuals/web_help/RAIM_P...

Now, things get even better if you use 4+ sats, or sats from different constellations (I am not sure how mature is cross-constellation data validation, however, so let's pretend 1 constellation for now). With 5 sats, the receiver can calculate the position even more precisely, determine the level of URE, etc. You can even detect that one source is unreliable, and discard it (effectively falling back to 4 sats). With even more sats you can (theoretically) do cool data analysis, where you can determine those factors even more precisely.

Now, add the inertial factors. Many passenger have either in-software (history of previous positions) or in-hardware (think accelerometers, magnetometers) inertial data sources. A sophisticated flight management software (FMS) can cross-corelate the inertial data with GNSS data and determine when the latter becomes unreliable.

All of those measurements and factors can subsequently be reported via ADS-B or ACARS, to help with fleet management, and general predictive maintenance. While aviation technology might sometimes look way out of date at a first glance, the modern airplanes have some really cool technology hiding in it.

I'm using data reported by aircraft equipped with ADS-B. Those aircraft broadcast their positions, and they include information about how much uncertainty they think is in their position estimate. When an aircraft that has been reporting low position uncertainty (< 1 nautical mile) starts reporting high uncertainty (> 4 nautical miles), it seems to correlate well with known areas of GPS interference, so that's what I use to make the map.

This paper describes in more detail some experiments using a GPS jammer and flying an aircraft around Edwards Air Force Base with ADS-B and what happens to the position reporting: https://web.stanford.edu/group/scpnt/gpslab/pubs/papers/Liu_...

gpx files sometimes include a sort of "precision" field[1]. Phyphox[2] also has a readout of the uncertainty: Location (GPS) -> Simple

[1] https://stackoverflow.com/a/9624761

[2] https://phyphox.org/