a new, highly resilient, unjammable GIS

sarabande

sarabande

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sarabande said:
is under development by BAESystems.

It collects signals from multiple and varied sources, and there appears to be no single point of failure *unless you count th ebatteries in th ereceiver as a SPOF).

A year or two away but on the horizon.

http://www.baesystems.com/product/BAES_052848/navigation-via-signals-of-opportunity-navsop?_afrLoop=1082910843385000&_afrWindowMode=0&_afrWindowId=null&baeSessionId=hSvzQ7bGNGpS87Q6jzLJBghRyQ5SGy22mYdcPl6P55ykTLqL2SZs!-853594562
Click to expand...

I hope you mean GPS; GIS is Geographic Information System, and is what I've spent many years becoming expert in ;)
 
It's not new at all!

I think it's actually quite an old idea and commercial companies have been doing it for some years.

1. Use the whole GNSS constellation, ie adding Glonass, Bidou/Compass and eventually Galileo to GPS.

2. Seek the ephemeris data from any communication source, eg via a mobile internet connection or via the GSM service itself (known as A-GPS). A much stronger signal is required to decode ephemeris broadcast from satellites than is needed to track position.

3. Use extended ephemeris prediction, with better algorithms and a better clock, thus allowing ephemeris to be prdicted from the Almanak for a day or two ahead rather than just for an hour or two.

4. Trilaterate using other signals. Two are very much used: GSM or UMTS (aka 3G) and UHF broadcast, especially from digital TV. A Cambridge based company (CPS) pioneered the first, and a US firm - now bust - the second. The problem BAE will have is the need to have LMUs (local measurement units, ie reference receivers measuring the precise timing of transmitters and relaying this information in some way, for instance over the 'user plane' of GSM signaling). You can't measure the timing once only, base-stations drift and have random jumps, which is why this method is still hardly used even 'tho it would be ideal for emergency services (the '911 problem' to those of us in the industry). It's also of limited accuracy due to the variability of the signal path - it's not 'line of sight', which gives a practical limit to the accuracy of around 50m.

5. One can also use a lot of less quantitative data such as which WiFi access points you can hear (if you got a good GPS fix and could hear 'BTHomehub34eb678' for instance, and then the GPS fades but you can still hear the home hub then you may not have moved far...' is the logic). Lots of phones, eg the iPhone, do this already.

I suppose you can add FM broadcast, time signals, Loran etc etc and use fuzzy logic or even Bayesian inference to combine all sources of data, but whatever it's a slow news day at BAE I think! In fairness to them, it's probably not been done to combine positions from the more accutate GPS 'P codes' with other sources since most research has been for commercial devices,in particular phones and so based on the publicly available C/A codes'

A couple of years ago I tried to get Trinity House to adopt these ideas for a GPS back-up rather than install an expensive Loran system, but they wanted their new toys (mind you, that was before austerity).

However there is an Achilles heel on nearly all these schemes (so maybe Trinty House had a point): how do we know that mobile phones or FM or TV broadcast will still work if GPS fails? It used to I grant, but I'm none too sure their resiliance is tested or reviewed any more!
 
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The trick is not in getting the positional information, as stated it is all out there just waiting to be used, the trick is in combining it in a way that actually gives you an accurate position, not so easy as you have to be able to instantly assess the quality of each bit of information and use the information accordingly. That is not so easy. Integrated nav systems have been around for many years using multiple inputs but they tend to be used by customers with deeper pockets than us yachties.
 
There is one SPOF in anything that relies on satellites - and that's the space segment. All satellites are vulnerable to an extreme solar event, such as the Carrington Event, and NASA acknowledge that it isn't practical to shield satellites against extreme flares. Events like that are rare, but they do happen, and would take out most of the GPS, Glonass or Galileo satellites, along with Iridium and so on.

All the other positioning methods mentioned don't work away from land - and reasonably civilized land, at that. OK for aircraft, which aren't likely to be landing at sea or in places where there isn't much infrastructure. Not so good for yachts.

A Carrington Event size of flare would also probably disrupt power lines and long distance cable communications; lesser flares have caused havoc in power-lines.
 
AntarcticPilot said:
There is one SPOF in anything that relies on satellites - and that's the space segment. All satellites are vulnerable to an extreme solar event, such as the Carrington Event, and NASA acknowledge that it isn't practical to shield satellites against extreme flares. Events like that are rare, but they do happen, and would take out most of the GPS, Glonass or Galileo satellites, along with Iridium and so on.
Click to expand...
Did the Carrington Event damage any satellites?
 
davidej said:
I've got a physics degree but couldn't understand a word of this.

Please explain without the jargon!
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Sorry, the usual problem of those involved in an area- it's quite hard to know what's jargon and what's just infrequently used english.

There are several satellite systems: US, Russian, Chinese and European (GPS, GLONASS, Bidou/Compass and Gallileo respectively). Combined these are known not as GPS but as GNSS (Global Navigation Satellite System).

Almanak and ephemeris are normal terms used for instance in celestial navigation - the position of the heavenly object as a function of time, expressed in geocentric coordinates. In our case satellites.

GSM and UMTS are our normal mobile phone systems, aka 2G and 3G respectively.

P and C/A codes are the military and commercial 'codes' respectively, as broadcast by GPS and which you have to know to understand the information coming from the satellite. GPS sets us yachties own use only the open, commercial, ones.

Fuzzy logic or Bayesian inference - sorry it would take too long and there are excellent Wiki pages. Bayesian inference is really important and is worth trying to understand since it forms the philosophical basis of so many important things, including medical diagnosis and jurisprudence.
 
RAI said:
Did the Carrington Event damage any satellites?
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If you read the story, you'll see it happened in 1859, so no. But it would have if there'd been any up there. It damaged long distance telegraph lines, which are a lot better protected by the earth's magnetic field and atmosphere than satellites are! In the web page I linked to, NASA acknowledge that it would be impractical to screen utility satellites from such an event, and that astronauts caught in an unscreened spacecraft would die. Manned spacecraft have screened areas to withstand such events these days, but if the Apollo astronauts had been caught by one while on the Moon, it would have been just too bad. Apollo, however, mostly happened during a period of low solar activity.

The Carrington Event was by far the largest such event observed - but ones at about half the strength are more frequent, and have caused major outages of power grids. We know from observations of ice cores that Carrington Event magnitude events have a timescale of about 500 years - but it is random, so the fact one happened 150 years ago doesn't mean it can't happen tomorrow.
 
AntarcticPilot said:
There is one SPOF in anything that relies on satellites - and that's the space segment. All satellites are vulnerable to an extreme solar event, such as the Carrington Event, and NASA acknowledge that it isn't practical to shield satellites against extreme flares. Events like that are rare, but they do happen, and would take out most of the GPS, Glonass or Galileo satellites, along with Iridium and so on.

All the other positioning methods mentioned don't work away from land - and reasonably civilized land, at that. OK for aircraft, which aren't likely to be landing at sea or in places where there isn't much infrastructure. Not so good for yachts.

A Carrington Event size of flare would also probably disrupt power lines and long distance cable communications; lesser flares have caused havoc in power-lines.
Click to expand...

The integrated systems I was knew of only took one element from space and thus could survive the loss of the space component. Yes large EMP events will spoil your day with most electronics, and although you can protect electronics from it in theory very very few people have ever been prepared to pay the cost of implementing such techniques.

Certainly for the time being integrated multi source navigation systems are well out of the cost range for normal sailors, but I can see the cost falling in the not so different future just as the cost of everything else electronic has.

One big question though is just how much we need it. We already 'integrate' the data from the sensors we have now, compass, sounder, log, gps, radar, etc etc to determine a position weighting the data according to our perception of it's relative accuracy. Perhaps all we really need is a few more sensors, a position by phone signal could be very useful when in coastal waters, using alternate space sensors to GPS may have benefits, and so on.
 
BAE makes its living off govt military contracts. Its sells screwdrivers at £500 per time complete with aircraft quality printing on the handle. It isnt into consumer electronics at affordable prices. But then no one has tried to jam my GPS signal yet, anyway.
 
matelot said:
BAE makes its living off govt military contracts. Its sells screwdrivers at £500 per time complete with aircraft quality printing on the handle. It isnt into consumer electronics at affordable prices. But then no one has tried to jam my GPS signal yet, anyway.
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The Messy Beast makes most of it's cash these days in the US and Saudi Arabia. As for the £500 screwdrivers, I suspect that is another urban legend, I was never able to get anything like that past a government auditor in the UK
 
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