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Tracker

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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

#9794 — Tracker

Hi

I am wondering whether a pi would make a good basis for a tracker? 
What I need is:

find its position by GPS
send position by SMS message every 30 minutes
5 days battery life
weight no more than 500 grams.

I suspect the battery life requirement makes this the wrong platform. 
If so, are there any other alternatives?

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

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#9795

On Mon, 12 Oct 2015 10:20:05 +0100, Alan Adams <alan@adamshome.org.uk>
declaimed the following:

>Hi
>
>I am wondering whether a pi would make a good basis for a tracker? 
>What I need is:
>
>find its position by GPS
>send position by SMS message every 30 minutes
>5 days battery life
>weight no more than 500 grams.
>
>I suspect the battery life requirement makes this the wrong platform. 
>If so, are there any other alternatives?

	I suspect the radios needed for GPS receive and SMS transmit will be
the real power drain (especially the transmit -- though keeping a GPS
module running can be a problem; if you don't keep it running you're going
to have start-up time every 30 minutes as the module re-fixes on the
satellites*). SMS implies using the cell-phone network, and those also take
a few minutes to fully negotiate a connection from a warm start.

https://www.youtube.com/watch?v=JbbYN0EZtBg
	Unfortunately -- discontinued: http://www.byonics.com/pockettracker/
	Also the problem that all their products are designed with Amateur
transmitters, not a module that can be connected to a cell-phone system.

	But I'd be tempted to agree that something like the R-PI is less likely
to be useful. The key feature I'd be looking for is a processor with a
hibernate mode with fast wake up, and auxiliary timing module that can wake
it up on some known period (every few seconds, perhaps -- long enough to
update a counter until the 30 minutes has gone buy, then run code to wake
up the GPS, capture a "stable" position, format/send via cell-phone system,
then shut down the radios and repeat). A $13 TIVA TM4C123 Launchpad**
perhaps (the Byonics units appear to use PIC chips). I don't recall if
Arduino has the hibernate capability. The TIVA 123 demo program includes
hibernation mode.



* First time start-up can take up to 12 minutes to capture the satellite
ephemeris data [especially on the older 8-channel sequential receivers,
12-channel parallel may be able to fill in the ephemeris using snippets
from multiple satellites).  Subsequent start-ups can take a few minutes
depending upon how far the unit has moved between activations.

** Getting the hardware isn't too difficult, though to get the $13 one
needs to navigate the Texas Instrument site itself; third-parties have
obscene mark-ups (TI was out of the TM4C1294 Launchpad when I was buying
them last year -- so I ended up paying near $50 for a $20 unit).
	It's getting the development environment that gets ugly. A port of
Arduino IDE -- Energia -- is available, but the heavy stuff (TI
CodeComposer Studio) requires signing your life away, and IAR&Keil
evaluation versions can only work within 32kB (CCS when used with a
Launchpad having the debug/emulator built-in is supposed to be "unlimited"
-- possibly useful given the smaller Launchpad has 256kB, and the larger
1MB).
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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#9799

On Mon, 12 Oct 2015 08:12:11 -0400, Dennis Lee Bieber wrote:

> SMS implies using the cell-phone network, and those
> also take a few minutes to fully negotiate a connection from a warm
> start.
> 
How high the thing being tracked will fly and where in the world it will 
do its flying, there may be a problem with cell-phone coverage. For 
instance, in the flatter parts of the UK the phone base stations have 
distinctly pancake-like coverage patterns. I've sat over the centre of 
Huntingdon at 3000ft, going slowly up in a nice thermal, and was unable 
to get any phone signal at all.

The HAB crowd all use lightweight, narrow-band kit in ham bands for 
telemetry and tracking.


-- 
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

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#9796

On Mon, 12 Oct 2015 10:20:05 +0100, Alan Adams wrote:

> Hi
> 
> I am wondering whether a pi would make a good basis for a tracker? What
> I need is:
> 
> find its position by GPS send position by SMS message every 30 minutes 5
> days battery life weight no more than 500 grams.
>
I just weighed my Pi, a 512MB model B mounted in a minimal 'case' (two Pi-
sized 3mm perspex plates with 4 metal pillars acting as spacers). This 
weighs 107.3g. What does your GPS receiver weigh? If it was me, I'd be 
looking at the USB-connected 'hockey puck' type, but have no idea of its 
weight or power consumption. 

Subtracting the weights of these from 500g will at least give you a 
ballpark weight for a battery which you can use to check out both 2 cell 
model aircraft Li-poly packs and/or the so-called 'portable mobile 
chargers', ie a case containing a Li-poly pack, v.reg and case with USB 
connector.

Have you talked to any of the HAB (high altitude balloon) enthusiasts? 
They know a lot about lightweight tracking systems and regularly fly 
RaspberryPi model As.

When you sat 'tracker', is this just a recorder, or does it also include 
a transmitter?

If it is just a recorder, I suggest you take a look at the position 
recorders used by glider pilots such as the EW Model D (these are now 
obsolete, so should be cheap on eBay), EW Microrecorder or LXnav's Nano. 
These weigh well under 100g and typically run for 12-24 hours on internal 
batteries. All (except the model D) accept external power for longer 
operating time and all have recording capacities of well over 5 days.
 
   
> I suspect the battery life requirement makes this the wrong platform.
> If so, are there any other alternatives?
>
What do you want to track? What are your weatherproofing and temperature 
insulation requirements?

Would something built round a PICAXE chip do the job? That would 
certainly be a lot lighter and (probably) use quite a bit less power. 


-- 
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

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#9797

In message <mvg8f1$khs$1@dont-email.me>
          Martin Gregorie <martin@address-in-sig.invalid> wrote:

> On Mon, 12 Oct 2015 10:20:05 +0100, Alan Adams wrote:

>> Hi
>> 
>> I am wondering whether a pi would make a good basis for a tracker? What
>> I need is:
>> 
>> find its position by GPS send position by SMS message every 30 minutes 5
>> days battery life weight no more than 500 grams.
>>
<snip>

> Have you talked to any of the HAB (high altitude balloon) enthusiasts?
> They know a lot about lightweight tracking systems and regularly fly
> RaspberryPi model As.

I've seen some discussion here about that topic.

> When you sat 'tracker', is this just a recorder, or does it also include
> a transmitter?

It needs to transmit the position, as a mobile phone text message. It 
can be pure GPS coordinated, as there's an i-Phone app to convert 
those to UK Ordnance Survey grid refs.

> If it is just a recorder, I suggest you take a look at the position
> recorders used by glider pilots such as the EW Model D (these are now
> obsolete, so should be cheap on eBay), EW Microrecorder or LXnav's Nano.
> These weigh well under 100g and typically run for 12-24 hours on internal
> batteries. All (except the model D) accept external power for longer
> operating time and all have recording capacities of well over 5 days.

>> I suspect the battery life requirement makes this the wrong platform.
>> If so, are there any other alternatives?
>>
> What do you want to track? What are your weatherproofing and temperature
> insulation requirements?

> Would something built round a PICAXE chip do the job? That would
> certainly be a lot lighter and (probably) use quite a bit less power.

There are commercially available pet trackers which come close, but 
most seem to be US based and I'm not sure whether those would work 
with the UK phone network. The one UK model I've found has a lot too 
many features, two-way voice call for instance, and puts the cost over 
100 pounds just for the hardware.

I'm looking at this for locating Duke of Edinburgh's award expedition 
groups. They need to carry it, hence the weight limit, and the Gold 
expedition runs for 4 days, hence the battery life limit. (It would be 
possible to exchange batteries each night if that proves essential.) 
The rate of travel is around 3 to 4 km per hour, so a position every 
30 minutes is adequate. We would be in areas of very poor mobile phone 
signal, so a text message has a chance of getting through while a 
voice call fails. There isn't enough coverage for data, so anything 
requiring an Internet connection won't work.

The whole thing needs to be fairly rugged, and moderately waterproof. 
It can be in a sealed plastic bag, and doesn't need to be accessed 
during the expedition.

Extra features which shouldn't add much to the complexity or power use 
could be a panic button, which sends an immediate update together with 
the word "emergency" for instance, and the ability to send to a list 
of maybe 3 phones. That would both allow for increased chance of 
receiving the message if the phones were on different networks or in 
different locations, and allow multiple supervisors to track all the 
groups.

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

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#9798

On Mon, 12 Oct 2015 13:50:47 +0100, Alan Adams wrote:

> In message <mvg8f1$khs$1@dont-email.me>
>           Martin Gregorie <martin@address-in-sig.invalid> wrote:
> 
>> On Mon, 12 Oct 2015 10:20:05 +0100, Alan Adams wrote:
> 
>>> Hi
>>> 
>>> I am wondering whether a pi would make a good basis for a tracker?
>>> What I need is:
>>> 
>>> find its position by GPS send position by SMS message every 30 minutes
>>> 5 days battery life weight no more than 500 grams.
>>>
> <snip>
> 
>> Have you talked to any of the HAB (high altitude balloon) enthusiasts?
>> They know a lot about lightweight tracking systems and regularly fly
>> RaspberryPi model As.
> 
> I've seen some discussion here about that topic.
> 
>> When you sat 'tracker', is this just a recorder, or does it also
>> include a transmitter?
> 
> It needs to transmit the position, as a mobile phone text message. It
> can be pure GPS coordinated, as there's an i-Phone app to convert those
> to UK Ordnance Survey grid refs.
> 
>> If it is just a recorder, I suggest you take a look at the position
>> recorders used by glider pilots such as the EW Model D (these are now
>> obsolete, so should be cheap on eBay), EW Microrecorder or LXnav's
>> Nano. These weigh well under 100g and typically run for 12-24 hours on
>> internal batteries. All (except the model D) accept external power for
>> longer operating time and all have recording capacities of well over 5
>> days.
> 
>>> I suspect the battery life requirement makes this the wrong platform.
>>> If so, are there any other alternatives?
>>>
>> What do you want to track? What are your weatherproofing and
>> temperature insulation requirements?
> 
>> Would something built round a PICAXE chip do the job? That would
>> certainly be a lot lighter and (probably) use quite a bit less power.
> 
> There are commercially available pet trackers which come close, but most
> seem to be US based and I'm not sure whether those would work with the
> UK phone network. The one UK model I've found has a lot too many
> features, two-way voice call for instance, and puts the cost over 100
> pounds just for the hardware.
> 
> I'm looking at this for locating Duke of Edinburgh's award expedition
> groups. They need to carry it, hence the weight limit, and the Gold
> expedition runs for 4 days, hence the battery life limit. (It would be
> possible to exchange batteries each night if that proves essential.) The
> rate of travel is around 3 to 4 km per hour, so a position every 30
> minutes is adequate. We would be in areas of very poor mobile phone
> signal, so a text message has a chance of getting through while a voice
> call fails. There isn't enough coverage for data, so anything requiring
> an Internet connection won't work.
> 
> The whole thing needs to be fairly rugged, and moderately waterproof. It
> can be in a sealed plastic bag, and doesn't need to be accessed during
> the expedition.
> 
> Extra features which shouldn't add much to the complexity or power use
> could be a panic button, which sends an immediate update together with
> the word "emergency" for instance, and the ability to send to a list of
> maybe 3 phones. That would both allow for increased chance of receiving
> the message if the phones were on different networks or in different
> locations, and allow multiple supervisors to track all the groups.

So it would not need to run continuously for five 24 hour days - that 
cuts your battery requirement about in half. I'd also suggest looking at 
a small solar panel (which could be attached outside someone's backpack) 
to either power directly or to recharge one of two battery sets while the 
other is in use.

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#9800

On Mon, 12 Oct 2015 13:50:47 +0100, Alan Adams wrote:

> I'm looking at this for locating Duke of Edinburgh's award expedition
> groups. They need to carry it, hence the weight limit, and the Gold
> expedition runs for 4 days, hence the battery life limit. (It would be
> possible to exchange batteries each night if that proves essential.) The
> rate of travel is around 3 to 4 km per hour, so a position every 30
> minutes is adequate. We would be in areas of very poor mobile phone
> signal, so a text message has a chance of getting through while a voice
> call fails. There isn't enough coverage for data, so anything requiring
> an Internet connection won't work.
>
Have you looked at any of the satellite-linked tracking systems? I know 
nothing about what is made and/or sold in the UK, but the Americans seem 
to like the SPOT2 and and the Delorme inReach systems. Both have a 'Red 
Button' help capability and the inReach offers 2-way text messaging, and 
those flying gliders in the US west tend to carry them because they can 
get a text message or position out when a satellite is in view. 

This link gives the inReach's capabilities, battery life, weight etc. as 
well as UK sources for it.

http://www.inreachdelorme.com/product-info/inreach-explorer.php
 
Both inReach and SPOT3 is available via Amazon UK - Spot 3 is around half 
the price of the inReach and a bit less capable (no free form TXT message 
transmission, I don't think it holds an internal copy of your track).

Both are fairly rugged and weight somewhere in the 100 -150g range, so 
comfortable under your 500g limit, even with a few sets of spare 
batteries.


> The whole thing needs to be fairly rugged, and moderately waterproof. It
> can be in a sealed plastic bag, and doesn't need to be accessed during
> the expedition.
> 
I think the above devices both fit these requirements.

There may well be other similar devices, but I haven't seen them 
discussed on rec.aviation.soaring, which is where I heard about these.

> Extra features which shouldn't add much to the complexity or power use
> could be a panic button, which sends an immediate update together with
> the word "emergency" for instance, and the ability to send to a list of
> maybe 3 phones.
>
When you buy one of these, you set up login on their website, pay for a 
satellite subscription (typically 12months) and register one (or more?) 
phones. I gather that they ring the phone(s) in an emergency, i.e. if the 
red button is pressed. You can use the website login to see where the 
device is on a map, follow progress, etc.


-- 
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

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#9801

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:

>> I'm looking at this for locating Duke of Edinburgh's award expedition
>> groups. They need to carry it, hence the weight limit, and the Gold
>> expedition runs for 4 days, hence the battery life limit. (It would be
>> possible to exchange batteries each night if that proves essential.) The
>> rate of travel is around 3 to 4 km per hour, so a position every 30
>> minutes is adequate. We would be in areas of very poor mobile phone
>> signal, so a text message has a chance of getting through while a voice
>> call fails. There isn't enough coverage for data, so anything requiring
>> an Internet connection won't work.
>>
> Have you looked at any of the satellite-linked tracking systems? I know
> nothing about what is made and/or sold in the UK, but the Americans seem
> to like the SPOT2 and and the Delorme inReach systems. Both have a 'Red
> Button' help capability and the inReach offers 2-way text messaging, and
> those flying gliders in the US west tend to carry them because they can
> get a text message or position out when a satellite is in view.

> This link gives the inReach's capabilities, battery life, weight etc. as
> well as UK sources for it.

> http://www.inreachdelorme.com/product-info/inreach-explorer.php

> Both inReach and SPOT3 is available via Amazon UK - Spot 3 is around half
> the price of the inReach and a bit less capable (no free form TXT message
> transmission, I don't think it holds an internal copy of your track).

> Both are fairly rugged and weight somewhere in the 100 -150g range, so
> comfortable under your 500g limit, even with a few sets of spare
> batteries.


>> The whole thing needs to be fairly rugged, and moderately waterproof. It
>> can be in a sealed plastic bag, and doesn't need to be accessed during
>> the expedition.
>> 
> I think the above devices both fit these requirements.

> There may well be other similar devices, but I haven't seen them
> discussed on rec.aviation.soaring, which is where I heard about these.

>> Extra features which shouldn't add much to the complexity or power use
>> could be a panic button, which sends an immediate update together with
>> the word "emergency" for instance, and the ability to send to a list of
>> maybe 3 phones.
>>
> When you buy one of these, you set up login on their website, pay for a
> satellite subscription (typically 12months) and register one (or more?)
> phones. I gather that they ring the phone(s) in an emergency, i.e. if the
> red button is pressed. You can use the website login to see where the
> device is on a map, follow progress, etc.

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.


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

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#9803

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:
> 
>>> I'm looking at this for locating Duke of Edinburgh's award expedition
>>> groups. They need to carry it, hence the weight limit, and the Gold
>>> expedition runs for 4 days, hence the battery life limit. (It would be
>>> possible to exchange batteries each night if that proves essential.)
>>> The rate of travel is around 3 to 4 km per hour, so a position every
>>> 30 minutes is adequate. We would be in areas of very poor mobile phone
>>> signal, so a text message has a chance of getting through while a
>>> voice call fails. There isn't enough coverage for data, so anything
>>> requiring an Internet connection won't work.
>>>
>> Have you looked at any of the satellite-linked tracking systems? I know
>> nothing about what is made and/or sold in the UK, but the Americans
>> seem to like the SPOT2 and and the Delorme inReach systems. Both have a
>> 'Red Button' help capability and the inReach offers 2-way text
>> messaging, and those flying gliders in the US west tend to carry them
>> because they can get a text message or position out when a satellite is
>> in view.
> 
>> This link gives the inReach's capabilities, battery life, weight etc.
>> as well as UK sources for it.
> 
>> http://www.inreachdelorme.com/product-info/inreach-explorer.php
> 
>> Both inReach and SPOT3 is available via Amazon UK - Spot 3 is around
>> half the price of the inReach and a bit less capable (no free form TXT
>> message transmission, I don't think it holds an internal copy of your
>> track).
> 
>> Both are fairly rugged and weight somewhere in the 100 -150g range, so
>> comfortable under your 500g limit, even with a few sets of spare
>> batteries.
> 
> 
>>> The whole thing needs to be fairly rugged, and moderately waterproof.
>>> It can be in a sealed plastic bag, and doesn't need to be accessed
>>> during the expedition.
>>> 
>> I think the above devices both fit these requirements.
> 
>> There may well be other similar devices, but I haven't seen them
>> discussed on rec.aviation.soaring, which is where I heard about these.
> 
>>> Extra features which shouldn't add much to the complexity or power use
>>> could be a panic button, which sends an immediate update together with
>>> the word "emergency" for instance, and the ability to send to a list
>>> of maybe 3 phones.
>>>
>> When you buy one of these, you set up login on their website, pay for a
>> satellite subscription (typically 12months) and register one (or more?)
>> phones. I gather that they ring the phone(s) in an emergency, i.e. if
>> the red button is pressed. You can use the website login to see where
>> the device is on a map, follow progress, etc.
> 
> 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.

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.

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.


-- 
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

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#9804

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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#9805

On 12/10/2015 20:15, Martin Gregorie wrote:

> That lack of good coverage is exactly why I suggested using a system with
> a satellite link:

SPOT systems don't work too well at UK latitudes, certainly in Scotland. 
There can be noticeable delays before they can uplink due to the low 
inclination of the satellites used.

Inmarsat for non polar regions and Iridium for all over the earth are 
the best solutions. However, worldwide connectivity with minimum latency 
comes at a price.

DeLorme units also use Iridium for the satellite transport. There are 
some issues with there SMS provision. You don't get a dedicated phone 
number with DeLorme, instead your SMS is sent from a pool of numbers you 
have little control over which is confusing for some recipients expect a 
message from a certain number.

Running an SMS gateway, with several hundred users sending SMS from 
remote rural locations, coverage by the UK networks is often surprisingy 
good from remote locations. Better from higher ground especially if it 
overlooks A roads or Motorways even if these are some miles distant. But 
you can't guarantee coverage for all 4 networks from the same rural 
location will be good. It depends on the network and the phone, 
especially the phone band in use.

My own satellite comms system is not used as a tracker but a method of 
guaranteeing SMS type connectivity when a mobile phone might not work. 
It also works worldwide without worrying about roaming charges etc. It 
consists of an rPi, an Iridium modem and a Wifi dongle. The modem is 
about the same size as an rPI board. The modem is powered from the USB 
connection on the rPi and understands Hayes modem AT type commands. The 
Pi runs up Linux and starts a Wifi AP plus some scripts in Python. You 
use your mobile phone to connect to the AP on the Pi and browse to a 
webpage generated by the scripts, fill in the fields with the message to 
send and away it goes. It normally takes about 20secs from hitting send 
for the message to arrive as an email on my server.

The modem is powered from the USB connection but only draws 95mA. It has 
a charger which uses 5V from the USB to charge up a 3F (farad) AeroGel 
capacitor. From cold it takes about 3mins to charge up ready for use. 
The power drawn during uplink is such that you get to send about 1 
message every 30secs max.

The Pi was the perfect solution for my needs. I was able to develop all 
the software in Python on a normal x86 Linux box. When working it was 
merely a case of making the necessary changes to put the Wifi on the Pi 
into AP mode and move the Python scripts. By using Linux + Python + the 
Pi's USB I was able to put the system together for the minimum of 
effort. Originally I was going to use a Bluetooth serial module 
available for a few pounds connected directly to the serial port of the 
modem. I'd have then needed to write an Android app to send the commands 
via Bluetooth to the module and hence modem. I'm very time poor but 
moderately cash rich, so spending 30ukp on a Pi saved me a huge effort 
in writing software (and learning about Android internals).

YMMV

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#9806

On Mon, 12 Oct 2015 13:50:47 +0100, Alan Adams <alan@adamshome.org.uk>
declaimed the following:

>
>I'm looking at this for locating Duke of Edinburgh's award expedition 
>groups. They need to carry it, hence the weight limit, and the Gold 
>expedition runs for 4 days, hence the battery life limit. (It would be 
>possible to exchange batteries each night if that proves essential.) 
>The rate of travel is around 3 to 4 km per hour, so a position every 
>30 minutes is adequate. We would be in areas of very poor mobile phone 
>signal, so a text message has a chance of getting through while a 
>voice call fails. There isn't enough coverage for data, so anything 
>requiring an Internet connection won't work.
>

	Given the nature of GSM, I suspect if a voice connection wouldn't get
through, neither would an SMS message -- since voice data is digitized for
GSM, no analog, it is just another data stream.

	However... Arduino world:
https://www.arduino.cc/en/Main/ArduinoGSMShield
(seems to have broken link for an image that is trying to load an edit
mode)

	And the other half of the equation:
http://www.adafruit.com/products/1272

	I'll have to confess I didn't check to see if the pin-outs conflict
between the two items.


>Extra features which shouldn't add much to the complexity or power use 
>could be a panic button, which sends an immediate update together with 
>the word "emergency" for instance, and the ability to send to a list 
>of maybe 3 phones. That would both allow for increased chance of 
>receiving the message if the phones were on different networks or in 
>different locations, and allow multiple supervisors to track all the 
>groups.

	Different networks for the receiving phones wouldn't be a factor --
once the SMS message is accepted by the ONE network the sender is using, it
is up to the network to route it -- SMS is a store&forward type protocol;
the message can be delivered whenever the recipient phone becomes
available.

	It really sounds like what you want are APRS (amateur radio) units.
There are a number made these days with both APRS protocol and GPS built
in. (Yaesu VX-8DR/-8GR; Kenwood TH-D72) Of course, you'd need a licensed
amateur with each radio.

	However -- battery life won't satisfy you... maybe 7 hours depending on
transmit power level, and beacon interval (some models have a "smart
beacon" mode which will send beacons based upon travel speed [and preset
mode: pedestrian, bicycle, motorized] and turns (since they send current
location, bearing, and velocity, they assume one will be on straight line
for some period of time before doing an update).
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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#9807

On 13/10/15 01:12, Dennis Lee Bieber wrote:

> 	Given the nature of GSM, I suspect if a voice connection wouldn't get
> through, neither would an SMS message -- since voice data is digitized for
> GSM, no analog, it is just another data stream.

AIUI, each GSM base station supports one control channel and one or more 
data channels. The control channel is used to signal the mobiles when to 
transmit, while the data channels carry voice. SMS is carried in spare 
capacity within the control channel.

The control channel is engineered to be more robust than the data 
channels, to avoid a 'runaway' mobile transmitting when it shouldn't. 
Hence the observation that text messages get through when voice fails.
-- 
Dave

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#9809

On 13/10/2015 09:59, dave wrote:
> On 13/10/15 01:12, Dennis Lee Bieber wrote:
>
>>     Given the nature of GSM, I suspect if a voice connection wouldn't get
>> through, neither would an SMS message -- since voice data is digitized
>> for
>> GSM, no analog, it is just another data stream.
>
> AIUI, each GSM base station supports one control channel and one or more
> data channels. The control channel is used to signal the mobiles when to
> transmit, while the data channels carry voice. SMS is carried in spare
> capacity within the control channel.
>
> The control channel is engineered to be more robust than the data
> channels, to avoid a 'runaway' mobile transmitting when it shouldn't.
> Hence the observation that text messages get through when voice fails.

+1

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#9802

On 12/10/15 10:20, Alan Adams wrote:
> Hi
>
> I am wondering whether a pi would make a good basis for a tracker?
> What I need is:
>
> find its position by GPS
> send position by SMS message every 30 minutes
> 5 days battery life
> weight no more than 500 grams.
>
> I suspect the battery life requirement makes this the wrong platform.
> If so, are there any other alternatives?
>
how will it send its position?

Arduino?


-- 
Global warming is the new Margaret Thatcher. There is no ill in the 
world it's not directly responsible for.

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#9808

Le 12. 10. 15 11:20, Alan Adams a écrit :
> Hi
>
> I am wondering whether a pi would make a good basis for a tracker?
> What I need is:
>
> find its position by GPS
> send position by SMS message every 30 minutes
> 5 days battery life
> weight no more than 500 grams.
>
> I suspect the battery life requirement makes this the wrong platform.
> If so, are there any other alternatives?
>

I think a simple microcontroller, like ATMega168 (like in arduino) with 
a GPS and GSM module can do a better work for less cost.

Franssoa

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