Author Topic: GPS after Brexit  (Read 15471 times)

Davef

Re: GPS after Brexit
« Reply #75 on: 23 August, 2020, 07:19:54 pm »
Almost all have some sort of electronic compass and various accelerometers. If it did not have a built in compass it could calculate a bearing by take two position readings maybe a few tens of metres apart, but I don’t know of any that work that way.

A few years ago compass chips were harder to come by and they all worked that way (I think they just took the bearing between the last two positions, so it could be uselessly noisy at low speed, even with a bit of low-pass filtering).  Indeed, my Vista HCx would  a) power down the compass and use this method to save battery when travelling above walking speed  and  b) had a menu option to turn the magnetic compass off entirely.

Not sure if modern ones still use GPS bearings while in motion, but it could be trivially tested with a magnet.
I can tell you that the iPad is not using gps for orientation as I just slowly rotated with google maps open. It smoothly rotated the direction thing. It then jumped the location by about 100m. (I am indoors so poor satellite signal) but maintained the correct orientation. Just going to look for some magnets !

Kim

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Re: GPS after Brexit
« Reply #76 on: 23 August, 2020, 07:21:56 pm »
I can tell you that the iPad is not using gps for orientation as I just slowly rotated with google maps open. It smoothly rotated the direction thing. It then jumped the location by about 100m. (I am indoors so poor satellite signal) but maintained the correct orientation. Just going to look for some magnets !

Yes, most smartphones and tablets have compasses (and 3-axis accelerometers) in them.  That's why those chips are now so cheap.

Now try the same test in a vehicle moving at speed.  Preferably not while driving it.

Re: GPS after Brexit
« Reply #77 on: 23 August, 2020, 07:23:58 pm »

Can you really do it with just an FPGA though? It's the GPS receiver chips that are supposed to do some pre-processing to stop reporting location data when they detect they are above 60,000 ft ASL or moving too fast (1000mph is often quoted as the limit).

Yes, because you use the FPGA instead of the GPS receiver chip. There are plenty of open source implementations out there.

Sorry, I was being pedantic about just an FPGA chip (and no antenna). Just an FPGA isn't enough, you need an antenna of some sort otherwise the FPGA has no signal to process. That's what I meant when I asked whether a SDR solution is enough, I guess it is.
"Yes please" said Squirrel "biscuits are our favourite things."

Re: GPS after Brexit
« Reply #78 on: 23 August, 2020, 07:24:58 pm »
Anyway, what a pedantic hill to choose to die on.
"Yes please" said Squirrel "biscuits are our favourite things."

Davef

Re: GPS after Brexit
« Reply #79 on: 23 August, 2020, 07:29:59 pm »
Almost all have some sort of electronic compass and various accelerometers. If it did not have a built in compass it could calculate a bearing by take two position readings maybe a few tens of metres apart, but I don’t know of any that work that way.

A few years ago compass chips were harder to come by and they all worked that way (I think they just took the bearing between the last two positions, so it could be uselessly noisy at low speed, even with a bit of low-pass filtering).  Indeed, my Vista HCx would  a) power down the compass and use this method to save battery when travelling above walking speed  and  b) had a menu option to turn the magnetic compass off.
Was that back when positional accuracy was 10m or so. You would have to travel several times that to get a decent bearing.

The eTrex 20 has no compass and was released in 2015.  Its GPS is a STA8088 TESEO II, I don't think there's been a significant improvement in accuracy since then?  A couple of metres is typical for my eTrex 30.
I was thinking last millennium with the 10m. I did not realise the etrex 20 had no compass. Etrex 30 did/does.

Davef

Re: GPS after Brexit
« Reply #80 on: 23 August, 2020, 07:37:03 pm »
I can tell you that the iPad is not using gps for orientation as I just slowly rotated with google maps open. It smoothly rotated the direction thing. It then jumped the location by about 100m. (I am indoors so poor satellite signal) but maintained the correct orientation. Just going to look for some magnets !

Yes, most smartphones and tablets have compasses (and 3-axis accelerometers) in them.  That's why those chips are now so cheap.

Now try the same test in a vehicle moving at speed.  Preferably not while driving it.
Well that was weird. Got my strong magnets (from a hard disk drive) and wafted them around my iPad. The direction showing in google maps did not change, but the position leapt a few metres as I past the magnets over.

simonp

Re: GPS after Brexit
« Reply #81 on: 24 August, 2020, 01:45:19 am »
It can possibly tell it’s not rotating from its accelerometers.

Re: GPS after Brexit
« Reply #82 on: 24 August, 2020, 08:55:55 am »
I’m sure it’s smart enough to filter out sudden strong magnetic fields. iPads themselves are full of strong magnets to attach the case.

The next experiment is to wave a magnet around while rotating it and see if it can still detect north.

Davef

Re: GPS after Brexit
« Reply #83 on: 24 August, 2020, 09:00:40 am »
I’m sure it’s smart enough to filter out sudden strong magnetic fields. iPads themselves are full of strong magnets to attach the case.

The next experiment is to wave a magnet around while rotating it and see if it can still detect north.
Yes indeed. The weird bit was not just the lack of effect on the direction, more the jump in location. At first I thought it just a random jump as I am inside with poor satellite reception, but it was consistent, each time I move the magnets over.

Tim Hall

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Re: GPS after Brexit
« Reply #84 on: 24 August, 2020, 09:14:52 am »
Anyway, what a pedantic hill to choose to die on.
My map shows it as a re-entrant.
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Davef

GPS after Brexit
« Reply #85 on: 24 August, 2020, 09:16:25 am »
Rotating the iPad and wafting magnets does seem to cause a bit of confusion but not much - it seems remarkably resilient

As I am indoors the gps is going to be inaccurate jumping around. I think the device is sensible ignoring these changes until there is some other trigger from the compass or accelerometer. Even though it ignores the compass change when there is no acceleration it still prompts it to update the gps derived position

frankly frankie

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Re: GPS after Brexit
« Reply #86 on: 24 August, 2020, 09:32:28 am »
The eTrex 20 has no compass and was released in 2015.  Its GPS is a STA8088 TESEO II, I don't think there's been a significant improvement in accuracy since then?  A couple of metres is typical for my eTrex 30.

The E30 turns its compass off at and above normal walking speeds, and (unlike the old Vista) it's non-negociable.  It's in the documentation somewhere.  The Etrex 10/20/30 were originally released in 2011, of course there've been several minor refreshes since then.
when you're dead you're done, so let the good times roll

Re: GPS after Brexit
« Reply #87 on: 24 August, 2020, 01:57:34 pm »
GPS tells you where you are.  Maps tell you what's there.  One is not a replacement for the other.
Kim said that ^

And I said that a map can tell you where you are.

GPS can also tell you where you need to go as well or are you deliberately ignoring that?

Plus a map won’t always tell you where you are depending on visible landmarks and the detail and scale  of the map.

So there you go Dave by your arguments you can’t navigate with a map.
If you are using GPS to mean a hand held GPS receiver like an etrex, yes it can tell you where to go using all the stuff it does in addition to receiving transmissions from GPS satellites to calculate your current lat,lon,alt and time. If you are using GPS in the strict sense that Kim appeared to be, meaning just Global Positioning System then all that does is give a position. It tells you where you are now, that is all. I was using it that second sense as I was responding to Kim.

Dave I include a quote of your original statement

Maps, both physical and mental, tell you where you are based on context. Most of the time , particularly on land, the function of a gps can be replaced with a map. A gps on its own without a map (possibly electronic) is not much use for navigation

It is stretching the bounds of credibility to suggest you meant the global positioning satellite system in isolation, when you refer to "the function of a gps" and "a gps". You clearly were referring to the devices we all use and hold in our hands not a bunch of satellites in orbit. Which incidently are no use to use to anyone without a suitable handheld device when out on a bike ride or walk! Just as mapping data held on the Ordnance Survey computers is of no use to anyone unless you can access a representation of it in some way via a handheld device or paper version.

Davef

GPS after Brexit
« Reply #88 on: 24 August, 2020, 02:21:07 pm »
GPS tells you where you are.  Maps tell you what's there.  One is not a replacement for the other.
Kim said that ^

And I said that a map can tell you where you are.

GPS can also tell you where you need to go as well or are you deliberately ignoring that?

Plus a map won’t always tell you where you are depending on visible landmarks and the detail and scale  of the map.

So there you go Dave by your arguments you can’t navigate with a map.
If you are using GPS to mean a hand held GPS receiver like an etrex, yes it can tell you where to go using all the stuff it does in addition to receiving transmissions from GPS satellites to calculate your current lat,lon,alt and time. If you are using GPS in the strict sense that Kim appeared to be, meaning just Global Positioning System then all that does is give a position. It tells you where you are now, that is all. I was using it that second sense as I was responding to Kim.

Dave I include a quote of your original statement

Maps, both physical and mental, tell you where you are based on context. Most of the time , particularly on land, the function of a gps can be replaced with a map. A gps on its own without a map (possibly electronic) is not much use for navigation

It is stretching the bounds of credibility to suggest you meant the global positioning satellite system in isolation, when you refer to "the function of a gps" and "a gps". You clearly were referring to the devices we all use and hold in our hands not a bunch of satellites in orbit. Which incidently are no use to use to anyone without a suitable handheld device when out on a bike ride or walk! Just as mapping data held on the Ordnance Survey computers is of no use to anyone unless you can access a representation of it in some way via a handheld device or paper version.
Thanks for letting me know what I meant. I can’t believe I thought it was not possible to navigate using a gps based navigation system when I do it pretty much every day, certainly every bike ride. I apologise.

Re: GPS after Brexit
« Reply #89 on: 24 August, 2020, 02:57:32 pm »
GPS tells you where you are.  Maps tell you what's there.  One is not a replacement for the other.
Kim said that ^

And I said that a map can tell you where you are.

GPS can also tell you where you need to go as well or are you deliberately ignoring that?

Plus a map won’t always tell you where you are depending on visible landmarks and the detail and scale  of the map.

So there you go Dave by your arguments you can’t navigate with a map.
If you are using GPS to mean a hand held GPS receiver like an etrex, yes it can tell you where to go using all the stuff it does in addition to receiving transmissions from GPS satellites to calculate your current lat,lon,alt and time. If you are using GPS in the strict sense that Kim appeared to be, meaning just Global Positioning System then all that does is give a position. It tells you where you are now, that is all. I was using it that second sense as I was responding to Kim.

Dave I include a quote of your original statement

Maps, both physical and mental, tell you where you are based on context. Most of the time , particularly on land, the function of a gps can be replaced with a map. A gps on its own without a map (possibly electronic) is not much use for navigation

It is stretching the bounds of credibility to suggest you meant the global positioning satellite system in isolation, when you refer to "the function of a gps" and "a gps". You clearly were referring to the devices we all use and hold in our hands not a bunch of satellites in orbit. Which incidently are no use to use to anyone without a suitable handheld device when out on a bike ride or walk! Just as mapping data held on the Ordnance Survey computers is of no use to anyone unless you can access a representation of it in some way via a handheld device or paper version.
Thanks for letting me know what I meant. I can’t believe I thought it was not possible to navigate using a gps based navigation system when I do it pretty much every day, certainly every bike ride. I apologise.

Well all your running around claiming you didn't mean handheld GPS (in the above statement) can't be used soley for navigation, has me confused.   How else are we meant to navigate by GPS, using signals received directly into a tin foil hat on our heads? What exactly did you mean by "a GPS" if not a handheld unit? ;)

Davef

Re: GPS after Brexit
« Reply #90 on: 24 August, 2020, 03:25:08 pm »
I was sloppy in my wording.

I was trying to say ...

A single point in 3 dimensional space and time (obtained through measurement of transmission times from at least 4 satellites of GPS or one of the other GNSSs or obtained otherwise) is insufficient to define a line segment that is needed as the basis of navigation.

A physical or mental model of the world together with what is observed at a point in the world might be sufficient to unambiguously determine the coordinates of that point and the orientation of the observer and therefore be sufficient for navigation.

Kim

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Re: GPS after Brexit
« Reply #91 on: 25 August, 2020, 12:50:48 am »
Well all your running around claiming you didn't mean handheld GPS (in the above statement) can't be used soley for navigation, has me confused.   How else are we meant to navigate by GPS, using signals received directly into a tin foil hat on our heads? What exactly did you mean by "a GPS" if not a handheld unit? ;)

He was following up from a statement I made, where I very much had a raw GPS chipset in mind as I wrote it.  Sure, it's not something you'd use to navigate on your bike or whatever, but it's the sort of thing I've used as a component in some other system to provide a location, speed or (more usually) an accurate time signal.  If I wanted to build a thing that could do any meaningful navigation, it would need (at a bare minimum) another set of coordinates in memory to compare to the current GPS position in order to produce some useful output.

Re: GPS after Brexit
« Reply #92 on: 25 August, 2020, 09:52:56 am »
Which means you can use a computer to read the map for you and successfully navigate by map, even if you missed second year Geography.

I can honestly say I have no idea how to read a map. I mean proper map reading with a compass and shit. And I didn't even miss second year Geography!

But did stick around for Higher level Information Technology and Computer Science (or alternatively are a 5yr old with a TV telecommand)

Edit: Sorry for the ambiguity. I was actually replying to Kim's comment, not making a personal remark!

Re: GPS after Brexit
« Reply #93 on: 25 August, 2020, 09:56:05 am »
What you describe is a map. A rudimentary one. A gpx unit that simply tells you your current location and nothing else on its own is no good for navigating.

Your stretching definitions here, but if we're playing that game...

If I was dumped in the middle of the Atlantic ocean in a boat with a GPS device that just told me my lat/lon I'd be able to navigate myself back to the UK much better than if I didn't have the GPS device.

No map required as I know the rough coordinates for the UK so all I need to do is point the boat in a vague direction that makes the GPS co-ordinates tick towards 51N,0E. That counts as a form of navigating to me.

You could even replace the GPS device with an accurate clock (at a known location) and a sextant (and with a bit of training) one would be able to do something similar.

Don't need map or GPS (or even compass)! Just row with the sun on your left cheek and trust your will to survive!! (and hope it rains or you could get very thirsty)

Re: GPS after Brexit
« Reply #94 on: 25 August, 2020, 10:10:13 am »
If I’m referring to features (that have been around more than 20 years) of handheld gps than yes.  There’s no way you were referring to anything other than handheld GPS in your original comment on this.

Dave you can’t try and prove a point you made by reducing handheld gps to something they are not.  As Greenbank says, your reductionist rhetoric is like giving someone a map with just contours 500m apart and saying go navigate.  Or having a map that doesn’t have street detail and saying go navigate to such and such a street using only the map we provide.

Simple fact is you can navigate by gps alone in a range of different circumstances and all on land.  To say otherwise is not to understand GPS or navigation or both.  You can navigate just using natural (or man made) features if you really wanted to.

You can navigate using just the bokel and asking the right questions - but you will need to have a description of where you want to go that he can relate to, which may bear no relation to real world features. This of course is a different view of navigation because you don't need to know where you are, only where you want to go. For most using a handheld navigation device is quicker and easier (but not half as much fun); for me who might speak more bokelish than IT this is not necesaarily the case!

Davef

Re: GPS after Brexit
« Reply #95 on: 25 August, 2020, 03:29:48 pm »
There is some evidence that mammals including humans have an ability to detect the earths magnetic field like migratory birds. If so it is very subconscious.

It has been suggested dogs rotating before lying down is mapping and there is the odd statistic that male dogs tend to orient themselves north/south when taking a dump.

Re: GPS after Brexit
« Reply #96 on: 25 August, 2020, 03:56:05 pm »
My (female) dogs always do a little twirly dance before they poo. I've never thought to check their orientation.

I'll make a spreadsheet and report back.

CrazyEnglishTriathlete

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Re: GPS after Brexit
« Reply #97 on: 25 August, 2020, 04:03:42 pm »
If civilian GPS were turned off now, the only people getting their Nandos from Uber Eats would be the ones who used their what3words address, and we don't want that to happen.

If I could hack my what3words address to pizza here now I'd never go hungry.   ;D
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Re: GPS after Brexit
« Reply #98 on: 25 August, 2020, 04:28:21 pm »
There is some evidence that mammals including humans have an ability to detect the earths magnetic field like migratory birds. If so it is very subconscious.

It has been suggested dogs rotating before lying down is mapping and there is the odd statistic that male dogs tend to orient themselves north/south when taking a dump.

All important research that got people an Ig Noble award:- http://www.frontiersinzoology.com/content/10/1/80

(From https://www.improbable.com/ig-about/winners/)

I think there was also some research of satellite photos that showed that cows like to stand facing North/South more than any other direction.

(Digs): Ah, here's a starting point: https://www.newscientist.com/article/dn14590-and-on-that-farm-the-cows-face-north-says-google/
"Yes please" said Squirrel "biscuits are our favourite things."

Re: GPS after Brexit
« Reply #99 on: 25 August, 2020, 04:48:28 pm »
I was sloppy in my wording.

I was trying to say ...

A single point in 3 dimensional space and time (obtained through measurement of transmission times from at least 4 satellites of GPS or one of the other GNSSs or obtained otherwise) is insufficient to define a line segment that is needed as the basis of navigation.


A point in space time, are we now time travelling as well? Giles fetch the Tardis ;D

So you’re saying if given a single coordinate , a once off , and no update if you move, then you can’t navigate? Bit like if you were given a 5m x 5m square of map, with a red dot saying you are here, that did not update as you moved?

Clearly you can still navigate by what you can see.  But you’re right, the single coordinate won’t necessarily help (much), on its own, just as the tiny fixed fragment of map won’t help you navigate.

But that’s a very long way from not being to able to navigate solely with a gps and your eyes.

If you think about it, you’ll also realise there are methods of navigation that are not point to point but based on terrain and / or valley systems. So not dependent on having a line segment as the basis.