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Re: Tracker

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In message <mvh0s4$qd6$1@dont-email.me>
          Martin Gregorie <martin@address-in-sig.invalid> wrote:

> On Mon, 12 Oct 2015 18:41:24 +0100, Alan Adams wrote:

>> In message <mvgqaf$lmb$2@dont-email.me>
>>           Martin Gregorie <martin@address-in-sig.invalid> wrote:
>> 
>>> On Mon, 12 Oct 2015 13:50:47 +0100, Alan Adams wrote:
>> 
<snip>

>> 
>> The snag with that is that the person doing the tracking may well be in
>> a poor signal area and unable to access the internet. Typical areas
>> would be the New Forest, where there's only a data connection in the
>> immediate vicinity of Lyndhurst and Brockenhurst, and Dartmoor where
>> away from Princetown you are isolated. The Lake District too is very
>> sparsely covered.
>>
> That lack of good coverage is exactly why I suggested using a system with
> a satellite link: if mobile coverage is so poor that the tracker, who is
> presumably in a campsite or motel near some town or village, is getting
> poor signal, then I wouldn't hold out much hope for the party being
> tracked being able to send any sort of message, even a text, especially
> as their phone will go through battery quite fast: if a phone can't
> contact a tower, it will set its transmit power to max and leave it there
> until it either gets a response or flattens its battery.

I don't see the system using a phone, but a phone dongle. The whole 
system would be powered down between 30-minute activations.

> The support group / tracker's connection is surely quite easy to solve:
> set up base where there is good phone coverage and a working internet
> connection. I don't know the New Forest, but in the Lake District I'd
> have thought somewhere like Penrith would have both mobile coverage and
> an internet connection - and maybe wifi as well.

The trackers aren't in a fixed location, but driving round visiting 
checkpoints. Occasionally they are able to drive to a high spot to 
pick up any awaiting text messages. As long as the message contains 
its send time, it's not critical if delivery is delayed.

> Apart from that all I can suggest is to make friends with a local radio
> ham and see what their relay networks have to offer and how heavy and/or
> expensive their transceivers are. Ask them about the 2-meter (144-146MHz)
> band, which has 5W hand-held transceivers that would fit your size/weight/
> ruggedness criteria. I've used this kit over flat land up to 3-4km
> without problems, however, I have a feeling it may not have the range you
> seem to need in more rugged terrian: without using repeaters the person-
> to-person range is suitable for use within a smaller town but would
> certainly be limited to a similar extent within a forest or among hills.

For some of these expeditions groups can be up to 20km apart, with 
staff similarly scattered.

We ran a complex Gold expedition on Dartmoor this year, and 
communication was almost entirely by text message. The beauty of text 
is that it does get through in difficult conditions - if the send 
fails, the message is re-presented and the sender can try again until 
it gets to the centrsl system. Then the central system retries until 
it gets to the end user.

Since a text only needs one network packet, instead of around 400 per 
second for voice, it's much less demanding.

This is why you can now register your phone with the emergency 
services, then in emergency communicate by text to 999. That's even 
better since it will use any reachable network.

Trying to get an internet connection so that a web based service could 
be used requires better signal even than voice.

-- 
Alan Adams, from Northamptonshire
alan@adamshome.org.uk
http://www.nckc.org.uk/

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Tracker Alan Adams <alan@adamshome.org.uk> - 2015-10-12 10:20 +0100
  Re: Tracker Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-10-12 08:12 -0400
    Re: Tracker Martin Gregorie <martin@address-in-sig.invalid> - 2015-10-12 16:38 +0000
  Re: Tracker Martin Gregorie <martin@address-in-sig.invalid> - 2015-10-12 12:18 +0000
    Re: Tracker Alan Adams <alan@adamshome.org.uk> - 2015-10-12 13:50 +0100
      Re: Tracker ray carter <ray@zianet.com> - 2015-10-12 14:10 +0000
      Re: Tracker Martin Gregorie <martin@address-in-sig.invalid> - 2015-10-12 17:23 +0000
        Re: Tracker Alan Adams <alan@adamshome.org.uk> - 2015-10-12 18:41 +0100
          Re: Tracker Martin Gregorie <martin@address-in-sig.invalid> - 2015-10-12 19:15 +0000
            Re: Tracker Alan Adams <alan@adamshome.org.uk> - 2015-10-12 21:02 +0100
            Re: Tracker mm0fmf <none@mailinator.com> - 2015-10-12 21:46 +0100
      Re: Tracker Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-10-12 20:12 -0400
        Re: Tracker dave <dave@cyw.uklinux.net> - 2015-10-13 09:59 +0100
          Re: Tracker mm0fmf <none@mailinator.com> - 2015-10-13 19:26 +0100
  Re: Tracker The Natural Philosopher <tnp@invalid.invalid> - 2015-10-12 19:24 +0100
  Re: Tracker franssoa <franssoa@email.invalid> - 2015-10-13 14:55 +0200

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