Do eTrex units wear out?

[drossall]

Even moving some tens of miles makes a difference for me. Am I imagining that?

[TimC]

Do 'consumer' GPSes even work in planes?
My phone (samsung galaxy S3) has excellent GPS reception, it even gets a signal indoors, but I tried it on a plane and it didn't work at all.

When you say you were in a commercial aircraft with "an unrestricted view of the sky" I'm not sure it's that unrestricted as the window's tiny. Were you in the cockpit?

Has anyone here ever tracked the route the plane's flying on their phone (or etrex or whatever)?  I thought it'd be quite interesting...

They don't work well in planes - you're sitting in a Faraday cage, after all. However, you can often get a signal if you're near a window. Ironically, we can't get a GPS signal on a hand-held device in the flight deck, as the windows contain a silver heating element that completely screens radio signals (all our aerials are mounted on the outside of the aeroplane or behind composite panels).  We did a trial on an iPad-based electronic flight bag last year and the only way of having the iPad update its position was to mount a remote Bluetooth GPS head on the door window in the forward galley!

[Ningishzidda]

Wait for the meteorite shower to pass, and try again.

[TimO]

You say that jokingly, but it's possible that a very high rate shower could cause problems. To be fair, I'm not talking about a regular shower, like the current Perseids with a ZHR of 60, but an unusual event with a rate of several thousand.  When meteors show a visible trail, that's plasma in the upper atmosphere, and there are a lot more non-visible trails. This is used for meteor scatter communications, but will also tend to block RF, and the GPS satellite are quite a way above this plasma. I'm not sure how many trails you would need to block GPS effectively, but an unusually high rate, as has been seen very occasionally in history could do thIs.  The meteor shower itself would be far greater news than any effect on GPS would be, because it would be impossible to miss meteors every few seconds, and the chances of this happening are pretty low, so I wouldn't hold your breath!

[frankly frankie]

Even moving some tens of miles makes a difference for me. Am I imagining that?

Maybe.  When the unit switches on it has an expectation of what sats it will be able to 'see' - and moving tens of miles isn't going to alter that much, several of them should still be accessible.  The 'warm start' routine should still apply.

re 'wearing out' - I suppose if some component gets tired that causes the internal GPS clock to become less accurate when the unit is switched off - that would be likely to lead to slower startup times.

[Ningishzidda]

IIRC, the satellites are in Medium Earth Orbit, so at the end of a 100, your GPS has lost the bunch it started with and acquired a new bunch during the journey.

The next morning, the bunch it finished with will be round the other side of the world, leaving the GPS unit having to lock on to another bunch, taking more time than you had expected.

[drossall]

It seems that you're correct. I never knew that. I had heard the received wisdom about taking longer in new locations, and indeed that fits roughly with my experience, but the explanation must be other than I've heard.

Except of course that, if you regularly start half-day rides from home* in the morning, the satellites that you finish by using will the be the same ones that you need for the next ride

* Or any other fixed location, obviously

[Ningishzidda]

I did hear of a US ‘Black ops’ project where the lucky individual is implanted with a ‘chip’ in the back of his neck; and this can be used via ‘Observation’ satellites to pinpoint his whereabouts, All recorded on computer.

[Kim]

IIRC, the satellites are in Medium Earth Orbit, so at the end of a 100, your GPS has lost the bunch it started with and acquired a new bunch during the journey.

The next morning, the bunch it finished with will be round the other side of the world, leaving the GPS unit having to lock on to another bunch, taking more time than you had expected.

True enough, but irrelevant. The receiver knows where the satellites are going to be for the next couple of weeks, because it has a model of their orbits in memory. What it doesn't necessarily know is its own location. So it starts off with where it was when switched off, and tries to find a solution. If that works, it's fairly quick. If it's moved too far it has to start from first principles.  If it's been off for weeks, it has to wait until the orbital data has been retransmitted before it can start to calculate a fix from first principles.  Hence the different times to acquire a fix in different circumstances. All assuming good reception -  if the signal is poor it will take even longer.

[Ningishzidda]

The general rule of thumb is to NOT rely totally on electronics. Learn to read a map. Learn navigation skills and go on a Bushcraft training course.

[frankly frankie]

As long as the sats don't fall out of the sky, the electronics are as reliable as the spare you carry.  Don't you?  I do.

[rogerzilla]

It was also next to useless in the Alps - couldn't see enough sky?

[Ningishzidda]

Garmin's 'Sats' did "Fall out of the sky"....

That's 'Sats' as in 'Customer Satisfaction Index'... 

[Greenbank]

It was also next to useless in the Alps - couldn't see enough sky?

Never had a problem with a GPS[1] when skiing in the Alps, no gaps or obvious jitter in the recordings...

1. Garmin Forerunner 405, Garmin eTrex H, Garmin Edge 705.

[Kim]

My original eTrex would often give extremely noisy readings and sometimes take ages to get a fix in very hilly terrain, just because it had fewer satellites to chose from, and some of those would be near the horizon where they'd be attenuated by local tree cover and the like.

This is the sort of situation that the newer chipsets (the 'H' series, and indeed the more recent ones with GLONASS support) really make a difference in.

[frankly frankie]

It's also a good idea (if you're as bulky as I am) not to lean over the thing and peer at it waiting for something to happen ...

I did hear of a US ‘Black ops’ project where the lucky individual is implanted with a ‘chip’ in the back of his neck; and this can be used via ‘Observation’ satellites to pinpoint his whereabouts, All recorded on computer.

D'you know what [POBI alert] - I'd vote for any party with 'personal tracking for all' on their manifesto.

[Ningishzidda]

The best policy with eTrex models with those crumby backplate mounts is to attach a lanyard for security when the mount breaks.
Be sure to have the lanyard short so the unit doesn’t drag on the tarmac. Then the eTrex unit won’t wear out.

[Charlotte]

The general rule of thumb is to NOT rely totally on electronics. Learn to read a map. Learn navigation skills and go on a Bushcraft training course.

Always carry a knife, a torch and something to start fires with.  Know how to live off the land and make sure that your blade has a sharp stabbing point and good cutting edges, because an artery torn through (as against a clean cut) tends to contract and stop the bleeding.

If a main artery is cleanly severed, your subject will quickly lose consciousness and die 

[Ningishzidda]

http://www.gooutdoors.co.uk/gerber-paraframe-1-knife-p279049


I got one for £15 cus it was in the display cabinet and they couldn't find the original packaging.

Lives in my Wallet pack. When someone says "give me ya wallet mate!", I show him the 'personal protection equipment' instead.

[Charlotte]

Lives in my Wallet pack. When someone says "give me ya wallet mate!", I show him the 'personal protection equipment' instead.

When you get stop/searched by the police and they question why you're carrying a knife with a frame lock - be sure to tell them that it's "for protection".

[Ningishzidda]

I also know how to kill someone with a Biro or sharp pencil, and one YACF parishioner suggests carrying one each of these in his H2G2 page.