RDF by mobile phone ?

[sarabande]

Whilst idly pushing back yet another prolapse today, I wondered if there is any means of using mobile phones as a form of direction finding.

Scenario:

Failure of all gadgetry on board incl, radar, depth meter, log, etc. All that still works, apart from the sails, is your mobile phone, which - as you are in the middle of the Channel / Sleeve - is showing No Signal.

With trepidation and circumspection you head towards the coast, and lo! up comes the phone with a decreasingly faint signal from your supplier.


Assumptions
That all phone masts have been installed and no more are being built.

That a phone mast handling a call has a unique ID.

That ID can be linked to a permanent fixed position on land.

That some means of extracting the unique ID is possible - perhaps by running the phone through a PC.



Result ?

This gives you a bearing to a transmitter of known height and position, and so a rough distance off.


Any comments or suggestions please ?

 

[nigelmercier]

This gives you a bearing to a transmitter of known height and position, and so a rough distance off.

How does it give you a bearing?

As an aside, I have heard of people sending themselves a text message while out of range, so their phone beeps "SMS" when they are close to land.

 

[Boathook]

The coastguard already use it for distress calls from mobile phones. I can't remember whether they have to request the info from the mobile phone companies or have it by default. They see which arials receive the phone transmission and draw circles round each based on the signal strength. The stronger the signal the closer the phone is to a mast. The demo I saw quite a few years ago would give an area such as a small town. As more aerials are installed this accuracy must improve.

I thought that recently someone was developing an 'app' for the smart phones to calculate all this.

 

[marklucas]

How does it give you a bearing.

You can only get position by interpolating multiple base stations' signal strength to get 3 or 4 range circles. You cannot get absolute bearing from a single base station, although some operator blessed apps may be able to tell you which sector is serving - but at best this would be 60 degrees - hopefully one's DR is better than that!

As the OP has assumed that the phone is working why not just use the in-built GPS that comes with any decent smart phone?

 

[dt4134]

You can't get bearing, only range, which can be determined pretty accurately, and if you have enough cells in range you can get an accurate position. I can't remember the parameter, something advance I think it is called. If you've got some spare time you can browse the 3GPP website which should give you all the answers you want. www.3gpp.org

As I understand it though it only applies to 2G cells not 3G cells.

 

[marklucas]

You can't get bearing, only range, which can be determined pretty accurately, and if you have enough cells in range you can get an accurate position. I can't remember the parameter, something advance I think it is called. If you've got some spare time you can browse the 3GPP website which should give you all the answers you want. www.3gpp.org

As I understand it though it only applies to 2G cells not 3G cells.

It will work with 3G but it is more complicated as 3G cells dynamically vary their (and consequently the phone's) power levels, whereas 2G will perhaps vary by time of day only.

 

[planteater]

My daughters ageing android phone doesn't have a GPS receiver but can manage extremely accurate positioning in towns, presumably based on range and bearing or triangulation between masts.

Haven't tried it at sea.

 

[lw395]

It works on time delay not signal strength.
I suspect you might find an issue when your phone can only see two basestations, each located in a coastal town. I bet the phone would assume the 'on land' solution to the ambiguity was the correct one!

 

[chanelyacht]

The coastguard already use it for distress calls from mobile phones. I can't remember whether they have to request the info from the mobile phone companies or have it by default. They see which arials receive the phone transmission and draw circles round each based on the signal strength. The stronger the signal the closer the phone is to a mast. The demo I saw quite a few years ago would give an area such as a small town. As more aerials are installed this accuracy must improve.

I thought that recently someone was developing an 'app' for the smart phones to calculate all this.

Sort of.

It's called EISEC, and it works due to how the phone mast is constructed. Most masts covering a circle are actually three 120 degree segments - some are 2 x 180, some 4 x 90. In most areas, each mast segment overlaps with it's nearest neighbours.

What we get is a %age probability for each segment, together with the OS grid coordinates for the masts, which means we can put an ellipse around an area.

BUT - and it's a big but - it is far from infallible. It doesn't work well with roamers (999 calls from, say orange but picked up by 02 - example only), it's not good for international numbers either - and the mast routing via the call handler is postcode linked, so it's quite possible for, say, Portland to get a 999 from the Isle of Wight (Solent CGs patch) or Falmouth to get one from the coast of west Wales.

It's better than nothing, and good for ruling out the loons from far inland who seem to think telling us a duck is drowning is a good idea, but as the only means of location - well, it gives us an area...sometimes.

Other times we don't get EISEC at all, for a variety of reasons.

No doubt though it will mature over time, but I can't see many more masts being built in our patch!

 

[ianat182]

How do the stolen car location devices work, could one of these be made to do the reverse task? I don't know what range they have or the equipment name.

ianat182

 

[maby]

How do the stolen car location devices work, could one of these be made to do the reverse task? I don't know what range they have or the equipment name.

ianat182

The more modern devices use GPS. The older ones use RDF with a network of base stations across the country, but they work on relatively low frequencies - compared with mobile phones, at least.

The problem with all these approaches at sea is that, for anything like an accurate fix you need at least three bearings (or ranges) from known locations distributed relatively uniformly aaaround you. By the time you get sufficiently far off-shore to really need RDF, all the cell towers that are remotely within range will be located in a small sector and unable to give you any very useful fix. The solution that the OP is looking far has been around since WW2 - it's called Loran - the transmitters are low frequency and far longer range, so you can get a decent triangulation from almost anywhere in the North Atlantic area at least.

 

[oldbilbo]

Scenario:

Failure of all gadgetry on board incl, radar, depth meter, log, etc. All that still works, apart from the sails, is your mobile phone.....

.....and your highly-trained, underpaid, pro navigator!

One who found, quite reliably and in proper succession, 'Draystone PHM', 'Breakwater Tower', 'New Ground', 'Melampus', 'S Winter', 'S Mallard', 'QAB SW Corner', then 'Plymouth', in a flash fog, when the 'lecky went completely tizup at the end of a ch'crossing a couple of years ago.

Didn't know 'Sara' was energetically trying all the numbers on his mobile with a tense and terse 'Wearthefrockarwe?' when I thought he was busying himself with the coffee and biscs.... O tempora, o mores!

 

[sarabande]

All characters, places, and events in any narrative in the colloquium quoted above are purely imaginary and bear no resemblance to reality.

 

[oldbilbo]

All characters, places, and events in any narrative in the colloquium quoted above are purely imaginary and bear no resemblance to reality.

KJB John 13: 38

 

[timbartlett]

.....and your highly-trained, underpaid, pro navigator!

Woss wunner them then? Surely any fule can see where the little triangle thingy is on a chart plotter? No need fer training.

 

[chanelyacht]

Woss wunner them then? Surely any fule can see where the little triangle thingy is on a chart plotter? No need fer training.

You'd be amazed the number of times we get given a position from the plotter in a distress situation - then when we ask again 3 mins later, the position is the same...

Right, so that's where your cursor is, now can you tell us where you are please....

 

[oldbilbo]

Woss wunner them then? Surely any fule can see where the little triangle thingy is on a chart plotter? No need fer training.

Aye, 'timbo', me ould mucker. Just about any fule k'n see where the little ∆ thingy is on a chart plotter - and many of them do.

The important issue is seeing where the little boat thingy is, actually, on a wide and windy sea. And many of them don't.

 

[sarabande]

there's this thing called eidetic mapping memory. Some former flying people have got it in spades...

 

[grumpy_o_g]

If you have an android phone then try an app called Antennas (sic). It's happily showing the range and bearing to a solitary mast on my phone at the moment (overlaid on Google Maps). It's taking my current position from the GPS though so it's sort of self-defeating for your purpose

 

[Beadle]

Sort of.

It's called EISEC, and it works due to how the phone mast is constructed. Most masts covering a circle are actually three 120 degree segments - some are 2 x 180, some 4 x 90. In most areas, each mast segment overlaps with it's nearest neighbours.

What we get is a %age probability for each segment, together with the OS grid coordinates for the masts, which means we can put an ellipse around an area.

BUT - and it's a big but - it is far from infallible. It doesn't work well with roamers (999 calls from, say orange but picked up by 02 - example only), it's not good for international numbers either - and the mast routing via the call handler is postcode linked, so it's quite possible for, say, Portland to get a 999 from the Isle of Wight (Solent CGs patch) or Falmouth to get one from the coast of west Wales.

It's better than nothing, and good for ruling out the loons from far inland who seem to think telling us a duck is drowning is a good idea, but as the only means of location - well, it gives us an area...sometimes.

Other times we don't get EISEC at all, for a variety of reasons.

No doubt though it will mature over time, but I can't see many more masts being built in our patch!

EISEC was (and still is) a landline system which gives the address of a 999 caller. It gathers its info from BT and other suppliers records.

On mobile networks it finds an approx position by using the sector of a "sectorised" cell the call is received in. The range is from the signal stength of he signal from the cellfone.

Hence the ellipse.

Not as good as the land based system - but a great improvement on nothing.

Ironically - getting more cellsites may not help much, increasing the number of sectors a site is divided into will give a more accurate bearing, whereas putting in extra sites will mean fewer but bigger sectors.

Of course the system is no help at all in telling the poor lost yachy where he is. So perhaps best, if you want help, to use VHF which will give a bearing to the Coastguard/ lifeboat.