Author Topic: GPS after Brexit  (Read 5972 times)

SoreTween

  • Most of me survived the Pennine Bridleway.
Re: GPS after Brexit
« Reply #50 on: August 22, 2020, 09:29:34 pm »
I concur.  A map conveys information about the environment.  A breadcrumb trail conveys information about a route.  A correlation between that route and ground features such as roads is a human convenience, it may be common but it is not at all prescribed by the terms.
2020 targets: None
There is only one infinite resource in this universe; human stupidity.

Re: GPS after Brexit
« Reply #51 on: August 22, 2020, 09:30:20 pm »
I will be less ambiguous. Just knowing your longitude and latitude and nothing else is not sufficient not for navigation. You need other stuff. Many gos devices provide other stuff other than position.

Re: GPS after Brexit
« Reply #52 on: August 22, 2020, 09:40:50 pm »
I will be less ambiguous. Just knowing your longitude and latitude and nothing else is not sufficient not for navigation. You need other stuff. Many gos devices provide other stuff other than position.

I don't think anyone is really disagreeing with you, you just seem to have picked a very strict definition of a GPS device which very few (given the number of mobile phones with mapping) fit within.

It's like saying: A map with just contour lines every 500m of elevation and nothing else is not sufficient for navigation (in the UK at least). You need other stuff on it. Many maps provide other stuff than just contour lines every 500m of elevation.

True, but a relatively pointless digression.

If I was dumped in the middle of the Atlantic ocean I'd rather have a device that could tell me my lat/lon than a map.

If I was dumped in the middle of Dartmoor or the Dales or the Peaks I'd rather have a good map than a device that could tell me my lat/lon.
"Yes please" said Squirrel "biscuits are our favourite things."

frankly frankie

  • I kid you not
    • Fuchsiaphile
Re: GPS after Brexit
« Reply #53 on: August 22, 2020, 10:50:00 pm »
Maybe one of the side effects of brexit will be to highlight all the idiots who've forgotten or never learned how to navigate with a map.

Might as well complain that nobody under the age of 50 knows how to use a slide rule.

I must admit my 1st thought exactly when reading the 1st quote above was "I must dig out my old book of log tables".  I could add it to my reading list, straight after the telephone directory.  It's 55 years since I had to refer to logs, and I never was progressive enough to own a slide rule.

Progress = dumbing down, just two ways of saying the same thing.

you only live but once, and when you're dead you're done, so let the good times roll

Re: GPS after Brexit
« Reply #54 on: August 23, 2020, 06:47:11 am »
I will be less ambiguous. Just knowing your longitude and latitude and nothing else is not sufficient not for navigation. You need other stuff. Many gos devices provide other stuff other than position.

I don't think anyone is really disagreeing with you, you just seem to have picked a very strict definition of a GPS device which very few (given the number of mobile phones with mapping) fit within.

It's like saying: A map with just contour lines every 500m of elevation and nothing else is not sufficient for navigation (in the UK at least). You need other stuff on it. Many maps provide other stuff than just contour lines every 500m of elevation.

True, but a relatively pointless digression.

If I was dumped in the middle of the Atlantic ocean I'd rather have a device that could tell me my lat/lon than a map.

If I was dumped in the middle of Dartmoor or the Dales or the Peaks I'd rather have a good map than a device that could tell me my lat/lon.
Anticipating the “what use is a piece of plain blue paper” I did say on land. I would say for marine navigation the most important thing is a compass. Without that it is very difficult to even go in a straight line especially when it is cloudy.

Re: GPS after Brexit
« Reply #55 on: August 23, 2020, 07:58:05 am »
GPS tells you where you are.  Maps tell you what's there.  One is not a replacement for the other.

But neither tell you where you want to go. For that, you need a piece of paper and a pen. 👍
I am often asked, what does YOAV stand for? It stands for Yoav On A Velo

Re: GPS after Brexit
« Reply #56 on: August 23, 2020, 09:44:54 am »
I'd quite like my etrex to have military grade GPS accuracy. I wonder how hard it would be - why aren't the more accurate signals made available to consumer devices?
Are they somehow more taxing to the satellite so that if millions of devices were using it, it couldn't cope.... Or is it just a security thing?
If it's the data, surely the information about exactly where I am standing isn't such a big secret... Or is it?

It's just the data.  The signal is a broadcast, so the satellite doesn't know or care who's listening.

It's a big secret because anyone who knows how to work balsa wood and an arduino could build a cruise missile around the civilian version, and the military would quite like the ability to turn that off, while still knowing where their planes and boats are.

(This is mostly 90s-era paranoia, when you mostly used GPS for navigating in the middle of nowhere.  Turning civilian GPS off now would be Bad, because boffins worked out how to use it for important things like synchronising the stock market.)

I think if I was whoever's being targeted by this balsa wood Arduino based missile I'd ideally like slightly more protection than simply its GPS being slightly wrong, but still  :)
It is what it is. It's not what it's not, so it must be what it is.

quixoticgeek

  • Mostly Harmless
Re: GPS after Brexit
« Reply #57 on: August 23, 2020, 11:06:32 am »

It's just the data.  The signal is a broadcast, so the satellite doesn't know or care who's listening.

It's a big secret because anyone who knows how to work balsa wood and an arduino could build a cruise missile around the civilian version, and the military would quite like the ability to turn that off, while still knowing where their planes and boats are.

(This is mostly 90s-era paranoia, when you mostly used GPS for navigating in the middle of nowhere.  Turning civilian GPS off now would be Bad, because boffins worked out how to use it for important things like synchronising the stock market.)

There's more to it than that. Any commercially produced approved GPS is supposed to have limits built into the device, called COCOM limits. Which basically say if you're going faster than a set speed, or higher than a set altitude, then the device turns it self off. The idea being to stop people making said Balsa cruise missiles.

The reality is that these days you can make your own gps receiver with an FPGA, or even just an SDR, which makes those limits a bit redundant. But it does raise the entry requirements for such an enterprise above the bare minimum technical competence.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Cudzoziemiec

  • Eating all the pies and drinking all the tea.
Re: GPS after Brexit
« Reply #58 on: August 23, 2020, 01:52:58 pm »
GPS tells you where you are.  Maps tell you what's there.  One is not a replacement for the other.

But neither tell you where you want to go. For that, you need a piece of paper and a pen. 👍
And a destination!
Faster than a walk, slower than a train, often slightly higher than a person. (David Byrne)

Re: GPS after Brexit
« Reply #59 on: August 23, 2020, 05:59:33 pm »
The reality is that these days you can make your own gps receiver with an FPGA, or even just an SDR, which makes those limits a bit redundant. But it does raise the entry requirements for such an enterprise above the bare minimum technical competence.

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).

An FPGA that speaks to a GPS chip can't bypass this as it should be the chip that enforces it. Not sure about an SDR approach though, not sure how easy it is to make an SDR listen on L1 (1575.42MHz) and then write the software to decode time/almanac/ephemeris/etc stuff.

(I might get an SDR capable of receiving that frequency and experimenting...)
"Yes please" said Squirrel "biscuits are our favourite things."

Re: GPS after Brexit
« Reply #60 on: August 23, 2020, 05:59:44 pm »

It's just the data.  The signal is a broadcast, so the satellite doesn't know or care who's listening.

It's a big secret because anyone who knows how to work balsa wood and an arduino could build a cruise missile around the civilian version, and the military would quite like the ability to turn that off, while still knowing where their planes and boats are.

(This is mostly 90s-era paranoia, when you mostly used GPS for navigating in the middle of nowhere.  Turning civilian GPS off now would be Bad, because boffins worked out how to use it for important things like synchronising the stock market.)

There's more to it than that. Any commercially produced approved GPS is supposed to have limits built into the device, called COCOM limits. Which basically say if you're going faster than a set speed, or higher than a set altitude, then the device turns it self off. The idea being to stop people making said Balsa cruise missiles.

The reality is that these days you can make your own gps receiver with an FPGA, or even just an SDR, which makes those limits a bit redundant. But it does raise the entry requirements for such an enterprise above the bare minimum technical competence.

J

As long as your missile isn’t flying over twice the height of Everest or travelling greater than 1100 mph it’ll be fine.

quixoticgeek

  • Mostly Harmless
Re: GPS after Brexit
« Reply #61 on: August 23, 2020, 06:11:03 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.

Quote
An FPGA that speaks to a GPS chip can't bypass this as it should be the chip that enforces it. Not sure about an SDR approach though, not sure how easy it is to make an SDR listen on L1 (1575.42MHz) and then write the software to decode time/almanac/ephemeris/etc stuff.

(I might get an SDR capable of receiving that frequency and experimenting...)

as I say, it doesn't need to talk to a GPS receiver chip, as you don't need it...

SDR's that work at that frequency are just fine. They are cheap and easy to get hold of.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Re: GPS after Brexit
« Reply #62 on: August 23, 2020, 06:13:06 pm »
I will be less ambiguous. Just knowing your longitude and latitude and nothing else is not sufficient not for navigation. You need other stuff. Many gos devices provide other stuff other than position.

I don't think anyone is really disagreeing with you, you just seem to have picked a very strict definition of a GPS device which very few (given the number of mobile phones with mapping) fit within.

It's like saying: A map with just contour lines every 500m of elevation and nothing else is not sufficient for navigation (in the UK at least). You need other stuff on it. Many maps provide other stuff than just contour lines every 500m of elevation.

True, but a relatively pointless digression.

If I was dumped in the middle of the Atlantic ocean I'd rather have a device that could tell me my lat/lon than a map.

If I was dumped in the middle of Dartmoor or the Dales or the Peaks I'd rather have a good map than a device that could tell me my lat/lon.
Anticipating the “what use is a piece of plain blue paper” I did say on land. I would say for marine navigation the most important thing is a compass. Without that it is very difficult to even go in a straight line especially when it is cloudy.

Navigating on land to a geocache. Navigating on land to the Greenwich Meridian. Navigating on land to the location of a crashed WW2 plane on a featureless upland bog. Navigating on land back to a car left in a large car park. Navigating on land back to a bike parked at a large control on PBP.

Re: GPS after Brexit
« Reply #63 on: August 23, 2020, 06:26:03 pm »
A gps on its own without a map (possibly electronic) is not much use for navigation

I Audaxed for 3 years with exactly that. The old yellow Garmin eTrex H with routes programmed with a routepoint labelled "L@T" or equivalent at each turn. No mapping at all. No breadcrumb trail. Got me 600km across Wales and back for example.

I also did the last 150km of a 200km Audax with no maps displayed on my Edge 705 after some water got into the slot that held the SD card with mapping data. All I had was the pink tracklog for the route and my current position. Took a few turns to get used to but then had no problem following it.

Just a GPS (and no other route info) would be a different prospect though.

I'd be fine with a map though, I spent years poring over them growing up and I'd be quite happy to navigate to somewhere completely new just looking at a map. Being able to look at a map and work out what you should be able to see at any point is a core skill that many people will now be missing.

Them: "We must be here."
Me: "No, we can't be there, otherwise there'd be a church up there on that ridge and there'd be a river over there. We walked past a lake a couple of minutes ago and there's a pub just up the road, of the 3 lakes in this area only one is near a pub and so I'd say we're probably here - if we walk this way for a couple of minutes we should see a junction on the left for Smith's Farm, if we don't see that then we'll stop and re-assess, otherwise we'll be going in the right direction and the footpath will be on the right after a further couple of minutes walk on that same road."
Them: "What? How can you tell that from just looking at a map?"
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.

It’s not a geographical map / a map representing a geographical area, which is I’m sure what you meant above.  Otherwise your statement about not being able to navigate with a gps without a map is null and void.  Which it is, whichever way you paint it.

For instance I could have a gps and a set of distances and bearings, to navigate by, which you’ll now be calling a map. Indeed it is if you consider it a set of instructions to get from A to B (possibly via C-Z)

I could do the same with a compass and bearings and pacing. Still a map if defined as a set of instructions etc.
A gps and a set of bearings and a compass is more than a gps. I was saying a gps that simply gives you your Lon and lat (like the very early ones), on its own, is no good on its own for navigating. Most devices are far more than simply a gps positioning device, they include various levels of mapping and navigation.  Given the choice of just a gps positioning device giving lot and lat or just a map, a map is the better option. Having both is better still.

Nope you can set the bearing and distance in the gps. Nothing is in addition to the gps.  Perfectly good for navigating in some circumstances particularly in the mountains. In fact in some circumstances where a traditional map is useless. There are myriads ways of navigating, many not involving a map.
If you are using gps to refer to the global position satellites and can be used to give you a position, no that does not give you a bearing. If you are referring to the handheld GPS receiver that has lots of other stuff in yes. Some have MP3 players too. 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.

Re: GPS after Brexit
« Reply #64 on: August 23, 2020, 06:38:06 pm »
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.

Re: GPS after Brexit
« Reply #65 on: August 23, 2020, 06:41:12 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.

Re: GPS after Brexit
« Reply #66 on: August 23, 2020, 06:43:19 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.

Re: GPS after Brexit
« Reply #67 on: August 23, 2020, 06:46:24 pm »
And from that people seem to think I am anti gps. Handheld gps devices are fantastic - I have owned gps devices since before they had screens and own several now. They are now sophisticated navigation devices providing much more than the position information provided by gps.

Re: GPS after Brexit
« Reply #68 on: August 23, 2020, 06:49:24 pm »
And from that people seem to think I am anti gps. Handheld gps devices are fantastic - I have owned gps devices since before they had screens and own several now. They are now sophisticated navigation devices providing much more than the position information provided by gps.

There you go wasn’t so hard to admit your you can’t navigate by (handheld) gps alone statement was wrong. ;D

Re: GPS after Brexit
« Reply #69 on: August 23, 2020, 07:01:01 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.

Kim

  • Timelord
Re: GPS after Brexit
« Reply #70 on: August 23, 2020, 07:08:04 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.
Careful, Kim. Your sarcasm's showing...

Re: GPS after Brexit
« Reply #71 on: August 23, 2020, 07:10:55 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.

Re: GPS after Brexit
« Reply #72 on: August 23, 2020, 07:14:25 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.
Or standing in one place and rotating slowly.

Kim

  • Timelord
Re: GPS after Brexit
« Reply #73 on: August 23, 2020, 07:18:28 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.
Careful, Kim. Your sarcasm's showing...

Kim

  • Timelord
Re: GPS after Brexit
« Reply #74 on: August 23, 2020, 07:19:28 pm »
Not sure if modern ones still use GPS bearings while in motion, but it could be trivially tested with a magnet.
Or standing in one place and rotating slowly.

That shows it's got a magnetic compass, but wouldn't test whether it switches to GPS-derived bearings when moving.
Careful, Kim. Your sarcasm's showing...