NAVSOP Navigation System Rivals GPS

dangle writes "BAE Systems has developed a positioning solution that it claims will work even when GPS is unavailable. Its strategy is to use the collection of radio frequency signals from TV, radio and cellphone masts, even WiFi routers, to deduce a position. BAE's answer is dubbed Navigation via Signals of Opportunity (NAVSOP). It interrogates the airwaves for the ID and signal strength of local digital TV and radio signals, plus air traffic control radars, with finer grained adjustments coming from cellphone masts and WiFi routers. In any given area, the TV, radio, cellphone and radar signals tend to be at constant frequencies and power levels as they are are heavily regulated — so positions could be calculated from them. "The real beauty of NAVSOP is that the infrastructure required to make it work is already in place," says a BAE spokesman — and "software defined radio" microchips that run NAVSOP routines can easily be integrated into existing satnavs. The firm believes the technology could also work in urban concrete canyons where GPS signals cannot currently reach."

Comments

Doesn't sound that accurate

[rossdee]

If its just using signal streangth then there are going to spots in cities or other cluttered terrain where it could be innaccurate. It would be ok if there is no terrain to interfere.

Re:Doesn't sound that accurate

[EdIII]

Each position's pattern of signals and signal strength is going to be unique

Unique at that moment in time. I change the wireless in my building and the signature changes. Wireless carrier changes something on a mast and the signature changes.

This can only work if you have a DB of precise locations of wireless signals. Even assuming that is viable, it cannot replace GPS as is.

Personally, I think we need less technology to pinpoint where we are. Trading convenience for security and privacy and all that.....

Re:Doesn't sound that accurate

[Jah-Wren Ryel]

Personally, I think we need less technology to pinpoint where we are. Trading convenience for security and privacy and all that.....

As a privacy and security freak I disagree. The problem is not location accuracy. It is information leakage. There are all kinds of great things I can do with my own location info. The problem is all the devices that gleefully hand over my location info to 3rd parties who wish to exploit it for their own benefit.

Re:Doesn't sound that accurate

[riverat1]

Use a real GPS unit with no broadcast capabilities and you don't have that problem.

Re:Doesn't sound that accurate

[evilviper]

This can only work if you have a DB of precise locations of wireless signals. Even assuming that is viable, it cannot replace GPS as is.

Whenever a program is looking-up the location of a smartphone, that phone is very probably also beaming back a list of all the Wifi APs in-range, their signal strength, and approximate location. Everyone who makes navigation software for smartphones is guaranteed to have such a database, and is continually keeping it up-to-date.

Not only is it practical to do this, and it has been for years and years, it's done because you're likely to get much better accuracy, and a much quicker location fix. You can prove this out by running a navigation app on a tablet that has wifi but lacks a GPS chip. You'll find that Google Maps or anything else has no problem at all pinpointing your location.

And BTW, moving one AP won't cause a problem... Triangulation requires several APs in range, and it'll try to use everything in-range to get a more precise fix so... Short of conspiring to have everyone in an area to move their APs in unison for a significant distance, you're not going to significantly fool the algorithm that handles all of this.

What's more... Before wifi was widespread, the previous fallback was a database with the GPS coordinates, altitudes, power levels, etc., of all of a telco's cell towers. It works, but not as well as the horde of prolific wifi APs these days. And for the record, I am speaking from first-hand knowledge.

Re:Doesn't sound that accurate

[Jah-Wren Ryel]

Use a real GPS unit with no broadcast capabilities and you don't have that problem.

And you also won't have the benefit of having a computer able to access your location data either. Seriously, that's a non-answer. We easily have the ability to do the right thing. Giving up on doing anything sophisticated just because there are groups who want to abuse it too is basically the historical definition of luddism.

Re:Doesn't sound that accurate

[vlm]

Use a real GPS unit with no broadcast capabilities and you don't have that problem.

And you also won't have the benefit of having a computer able to access your location data either.

Why? Since I've done it, and its common knowledge how to do it, I'm thinking thats just wrong. Hard to believe its been over a decade since I was experimenting with ham radio APRS using a GPS, simply unplug the transmitter/set the broadcast timer to zero (or a billion) and you're done. Ever since the first NMEA output jack on a GPS in the 90s, people have been hooking them up to laptops and fooling around with big screen navigation displays (like a giant aircraft HSI, but for boats), homemade boat autopilots, automatic fishing trawling autopilots, homemade moving maps, stuff like that. The GPSD daemon has been around for I believe 18 years now, so 18 years ago it changed from a curiosity/hack to a very standardized interface. GPSD is currently maintained by ESR, you may have heard of him over the decades.

The only reason "your" computer aka cell phone broadcasts your GPS position without any control by you is because you bought into a walled garden. Its not your phone, and its not working for you.

Re:Doesn't sound that accurate

[Anonymous Coward]

All true. Right now the only "safe" GPS devices are those which have no capability of being connected to anything. It doesn't have to be that way. In-car navigation systems could be designed to not reveal your location to anybody except you. They could have a button on the dash that says "transmit my location" if you want to use the services of a central office. The car could only transmit that data itself in case of an accident, assuming of course you gave it permission in advance to do that. You could have a phone or computer app that would tell YOU where your car is instead of some central monitoring station, and YOU alone could have the ability to disable your vehicle, which would be appropriate since you'd be the only one who knows where it is.

Also, your smartphone could easily keep logs of "I told your location to X at these times during the day" and other such sensitive data like that. Everybody likes to use phone logs against people, why can't we use them FOR people for a change?

All of this is possible, but nobody seems to build it. I wonder why that is?

For now, remember that if your device can act intelligently on your location, it can and probably does do so for someone else's purposes too. If there is a microphone that you don't have a physical plug or off switch to, somebody besides you can turn it on and off. Your modern conveniences might provide some convenience for you, but they are VERY convenient for law enforcement on fishing expeditions, private investigators bribing system operators, etc.

What? Like assisted GPS (A-GPS)?

[Mr0bvious]

Google has been using this for some time and is used on Android devices - you can see their patent here: http://www.google.com/patents/US7532158

A-GPS is not new (http://en.wikipedia.org/wiki/Assisted_GPS), though they seem to want to extend it to other radio sources.

Re:What? Like assisted GPS (A-GPS)?

[wvmarle]

A-GPS still uses only GPS signals for positioning, but gets help from a data network (not necessarily mobile). Basically it receives certain orbital info of GPS satellites that are normally transmitted on the GPS signal itself. But regular GPS data is slow, it can take ten minutes or more to get all data complete. Over the network it's a fraction of a second. This often helps getting a fix much faster than with plain GPS, but the location itself is pure GPS based.

Some phones may also use the mobile network for triangulation, independent from GPS, and usually less accurate.

Relying on third party wifi inspires confidence.

[nzac]

Sure in an open area the signal strength from broadcast and third-party location services is fine but so is GPS.

But in an urban environment these are not accurate signal strength is only loosely proportional to inverse square of the distance so any accuracy will utterly break down. I can't see them having the money investing on getting a location DB for coverage outside major cities meaning you have to ship an unusable feature to most of the population.

The firm believes the technology could also work in urban concrete canyons where GPS signals cannot currently reach.

This will only work by regularly updating a database of local signals by driving down these roads and walking around areas. You might get the reliability for a consumer device but SDR like this can hardly be cheap, small and low power.

Possibly they have algorithm to make this manageable but i would think installing purpose built transmitting devices at every street corner would be a better option.

Re:Made in Britain, not for the rest of the world

[wonkey_monkey]

So your sole criterion for something being completely useless is that it doesn't work 3 hours north of Perth? I look forward to your input when the next article on deep-sea submersibles comes along.

How NAVSOP works - from the developer

[Anonymous Coward]

Hi All

It's great to see this much interest in NAVigation via Signals of OPportunity. I can't reply to everyone individually and certainly can't get into huge discussions, I've scanned this thread and thought I could give you some information to help clear some of the mist.

1 - Radio positioning is certainly not new, people are discussing Rosum here, and (in a round about way) Cambridge Positioning Systems - the latter funded my PhD at Cambridge in this topic, and I've been driving developments in this field for the last 5 years. I'm not claiming to have invented multilateration or opportunistic positioning, what we have been doing at BAE is working on removing a lot of the restrictions discussed on here - for example getting rid of the need for access to a database someone else created of all the transmitter locations, or access to differential corrections from a reference receiver. A lot of the "this is not new" comments refer to differential positioning using reference receivers and having access to databases of transmitter locations (Rosum, the old Cursor positioning system from Cambridge Positioning Systems, etc). We consider those aspects to be undesirable constraints on a flexible opportunistic positioning system and don't rely on them. The system determines the transmitter locations itself, or gets by witout actually needing to locate the transmitters at all (for example our indoor positioning system does not aim to or need to locate the transmitters to function) We have developed some Simultaneous Localisation and Mapping algorithms (again not pretending to have invented the concept, just developing new algorithms building on these methods for use in opportunistic radio positioning) to aid the learning process and allow operations during GPS denial but before any transmitters have been fully calibrated via GPS, and we also exploit the fact that we are not limiting ourselves to jerry-rigging existing devices (e.g. cellphones) to do things they weren't designed for. We also look at some exotic concepts that are too computationally expensive or demanding in hardware to ever be applicable to the civilian sector, but are applicable to other sectors.

2 - We record as many metrics as we can - phase, phase rate, arrival of certain repetitve signal structure (time of arrival), signal strength, etc. We use different metrics in different environments - for example signal strength is more useful indoors to discriminate motion than outdoors. See my ION paper for more on the indoor system http://www.plansconference.org/abstract.cfm?meetingID=36&pid=51&t=C&s=1

3 - The entire concept is based around learning - the system gets better with use. When GPS is available you can start learning about the locations of the transmitters around you, their signal stabilities, start recording signal strength fingerprints, etc. Most (but not all) types of radio transmitter can be localised by our techniques. So imagine driving into a city along a motorway - you start to learn about the DAB transmitters, DVB, cellular etc available and start to localise them. Even without fully determining their location you quickly determine what driving East looks like in "radio eyes" versus driving North based on relative arrivals of repetitive timing structures within digital broadcasts, etc. So already you can handle short dropouts and freewheel through short GPS dropouts (a few minutes) using the opportunistic radio data with only a few minutes of operation. The further to go and more you have the system on, the better, and eventually you work out where all the transmitters are (short range cellular are located very quickly, long range DAB, DVB etc take more time to locate). Eventually you have enough data to confidently state where the transmitter is and it goes in the database. These signals punch into cities much better than GPS, so calibrating these sources on the way in means that you can use them during GPS dropout inside the city. The accuracy depends on a whole host of factors - typically ~10-150 metres, and