ALoveSupreme wrote (see)

£90 a year, and your wife knows where you are?

Actually my mother was banging on about getting one for me from santa this year, the girlfriend agrees but I have mixed feelings.

Mind you if santa brings it and it keeps them happy the only thing I have to worry about is the weight.

> To get  true dimentional fix, it actually requires three or more cellmast sites to lock onto the signal. Two will only give a point to point distance between the two.

Two cell site measurements will produce two distance measurements from signal time of flight (TOA or TDOA), which gives two intersecting circles.  The phone lies at one of two intersections.  i.e. you have an ambiguity of which of the two points the phone lies.  Adding a third measurement resolves the ambiguity.

But yes, to get an unambiguous 2D fix you need three cell site measurements

Quite a nice little Overview of Location Technologies

sounds like a good idea to me

I wouldn't mind paying the £150 one off fee but £90 a year on top is a bit steep! 

> The SPOT uses sattelites to locate, not phone masts

Yes, we know... 

Tony and I were talking about the options already available to the emergency services, and how any mobile can be located by triangulating its signals from three base stations.

The Spot has nothing to do with phone masts and does not technically 'use' the satellites to determine a position (i.e. triangulate etc.) - it uses GPS to 'determine' the position then 'broadcasts' it by satellite.

So (as they say) works where phones do not...

You can actually get them for about 100 pounds (in the UK) and the standard service is about 100 dollars (so only about 50 pounds) per year!

Although realistically the uprgade (50 dollars) for the tracking service is well worth it!

Reason to get one - so people know where you are.

Reason not to get one - see above.

Barking Mad 2 wrote (see)

The Spot has nothing to do with phone masts and does not technically 'use' the satellites to determine a position (i.e. triangulate etc.) - it uses GPS to 'determine' the position then 'broadcasts' it by satellite.

So (as they say) works where phones do not...

WTF! A GPS receiver is satellite dependent, SPOT is GPS dependent ergo it is satellite dependent, in fact it is a GPS receiver that uses navigation satellites and comms satellites. GPS receivers do use satellites, GPS coordinates cannot be determined without them.

GPS is a system (that's what the S stands for) and the two most important parts of that system are the microwave signal transmitters, housed in navsats and the receivers, those things we hold in our hands and loosely refer to as GPS. Spot could not work if it couldn't first receive those signals, from the nav sats, to determine its position etc. which data can then be transmitted to a comsat for onward transmission to a monitoring station.

You must be "East Ham" to think otherwise.

SPOT - how it works

.

And as CP has said,

Of course we know that Spot is totally satellite dependant as opposed to mobile phones. (as pointed out above by Jugears) We were discussing the fact that if you ring 999 on your mobile, we in the emergency services can instantly pinpoint the position of the phone with a great deal of accuracy.

That aspect had been introduced into the thread as a reason why it is better than a mobile phone which is complete nonsense.

Obviously, SPOT does have an advantage in the remoter parts of the country where there is poor/no phone coverage, but for the average walker on this site, the mobile is generally all that is required in an emergency and as has been pointed out by others, can give the emergency services the opportunity to actually talk to the person(s) needing help which in turn means that they can respond appropriately and proportionately.

It's a pity some cannot read what has actually been said before jumping in with both size tens!

cysgod-du (Grand Slam 2008) wrote (see)

Obviously, SPOT does have an advantage in the remoter parts of the country where there is poor/no phone coverage, but for the average walker on this site, the mobile is generally all that is required in an emergency and as has been pointed out by others, can give the emergency services the opportunity to actually talk to the person(s) needing help which in turn means that they can respond appropriately and proportionately.

That's what I mean, most people on here don't visit the remote parts of Scotland and there are not that many places south of the border that doesn't have a signal over vast areas unlike in your neck of the woods.

The infrastructure is improving all the time too.

In South Wales we have the second highest cell mast site in the UK which is evident as we take mobile 999 calls from all over the southern part of th UK and the Midlands of England.

We regularly take calls from afar afield as Cornwall to Birmingham!

The lack of cover in Scotland must annoy business interests!

To clarify - what I meant was it does not use the 'Spot' satellites for determining a position - but yes of course it uses 'GPS' satellites to determine position and the Spot satellites to broadcast your position out.

Of course if you had a phone and crucially a decent 'signal' then you would probably just call - but the whole point of this is that is works where mobile phones do not.

As for 'infrastructure is improving all the time' - yes I agree but I am pretty sure there are plenty of more remote areas that realistically will never get coverage and Spot is not just for the UK where we 'generally' have good cellphone coverage.

You can just be a few miles out of Ambleside and find yourself with no coverage on either O2, Vodafone or Orange (various members of the party had different phones - none worked). I have looked at the coverage maps for various mobile phone companies - would say they are often a bit 'optimistic'.

Something like Spot is not for everyone and certainly not really needed if you always walk where there is phone coverage or in groups but the tracking is a nice 'extra' feature and for about £100 initial cost and the equivalent of just over £4 a month (about £6 with tracking) is not 'expensive' and I am sure will save some lives.

The major drawback with such technology from the Emergency services point of view is that they are not capable of defining the "emergency" because they are a one way device.

Where there is mobile phone coverage, then the call takers can obviously determine from the caller the nature of the call and can then deal with the call appropriately and proportionately.

One person's "emergency" is another's routine incident, and unfortunately, the individual is sole judge of fact as to what at the material time constitutes an "emergency."

The reasonable costs also mean that such technology would be within the reach of the "numpties" who might misuse the system.

This has happened to a large extent with mobile phones, but at least it is possible to interrogate the user,and eliminate at source the "disruptive" misuse of the 999 system.

You will be surprised at the numbers of 999 calls we get from people defining what they constitute an emergency, which is nothing of the sort. What sanctions would there be if someone triggered a SPOT call accidentally or inappropriately and a full scale search and rescue mission was initialised?

Rather than embracing such extravagant technology, it might be better to go for a more comprehensive cell phone coverage or develop further two way satellite phone technology for a truly comprehensive emergency system.

Of course that would mean a little more expense, but making technologies available to the masses by cutting corners on costs is not necessarily a good thing if you desire the quality of a system!