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Earlier today there was a thread running about the OS Locate app to which I contributed. It has now disappeared and a search for 'locate' gives no results. Where has it gone?
In reply to keith-ratcliffe:
Can you use the os locate app to locate the location of the lost os locate app thread?
Can you use the os locate app to locate the location of the lost os locate app thread?
19
In reply to Morty:
By coincidence I am currently reading the Stephen Hawkind book and grappling with the Heisenberg Uncertainty Principle - is this a case in point? I can know about the existence of the thread but not at the same time know its content. So perhaps if I deny its existence then the content will be revealed.
By coincidence I am currently reading the Stephen Hawkind book and grappling with the Heisenberg Uncertainty Principle - is this a case in point? I can know about the existence of the thread but not at the same time know its content. So perhaps if I deny its existence then the content will be revealed.
7
In reply to keith-ratcliffe:
I've been looking for it too. Not a scooby!
> Earlier today there was a thread running about the OS Locate app to which I contributed. It has now disappeared and a search for 'locate' gives no results. Where has it gone?
I've been looking for it too. Not a scooby!
In reply to keith-ratcliffe: Odd that it seems to have been removed Especially since ukhillwalking did an article about it a couple of months ago
https://www.ukhillwalking.com/news/item/70813/mrt_in_smartphone_appeal_to_w...
https://www.ukhillwalking.com/news/item/70813/mrt_in_smartphone_appeal_to_w...
In reply to keith-ratcliffe:
It's still cached on Google's servers, it's pretty obvious why it didn't last long:
https://webcache.googleusercontent.com/search?q=cache:paKT8WfKa9wJ:https://...
It's still cached on Google's servers, it's pretty obvious why it didn't last long:
https://webcache.googleusercontent.com/search?q=cache:paKT8WfKa9wJ:https://...
In reply to EddInaBox:
Thanks for this - I didn't know about this way of accessing stuff.
However there were about 20 more posts since that cache that contained some interesting content.
I am also interested to know why you think it didn't last long.
Thanks for this - I didn't know about this way of accessing stuff.
However there were about 20 more posts since that cache that contained some interesting content.
I am also interested to know why you think it didn't last long.
In reply to keith-ratcliffe:
A brand new user, starting a single thread on the day they registered which contains a link to a commercial site, and not contributing to any other threads, that will get the UKC Spam-Hounds' noses twitching.
A brand new user, starting a single thread on the day they registered which contains a link to a commercial site, and not contributing to any other threads, that will get the UKC Spam-Hounds' noses twitching.
In reply to EddInaBox:
I did note the commercial reference but also one of the replies was very critical of the credentials of the original poster.
I learnt a lot from the subsequent exchanges and wanted to follow the story.
I did note the commercial reference but also one of the replies was very critical of the credentials of the original poster.
I learnt a lot from the subsequent exchanges and wanted to follow the story.
In reply to keith-ratcliffe:
There is a cached page
http://webcache.googleusercontent.com/search?q=cache:https://www.ukclimbing...
The original poster does seem to be plugging either the app or the navigation school
There is a cached page
http://webcache.googleusercontent.com/search?q=cache:https://www.ukclimbing...
The original poster does seem to be plugging either the app or the navigation school
In reply to Dave the Rave:
The thread vanishing confused me too, especially as I'd just typed a reply and got met with a 'no such thread' error when posting.
Jist I can remember from the missing comments (can't remember who - sorry):
- Locate app didn't work well in Cairngorms, showing the wrong 'sheet number' (though I didn't think that OS Locate showed sheet numbers), so they used another app which seemed to more reliably give 10-fig refs.
- GPS can accurately tell you it's precision, but not its accuracy. (Yet more confusingly, an ISO standard defines accuracy as 'comprised of trueness and precision' - https://en.wikipedia.org/wiki/Accuracy_and_precision )
- Typical GPS precision on a modern smartphone is
The thread vanishing confused me too, especially as I'd just typed a reply and got met with a 'no such thread' error when posting.
Jist I can remember from the missing comments (can't remember who - sorry):
- Locate app didn't work well in Cairngorms, showing the wrong 'sheet number' (though I didn't think that OS Locate showed sheet numbers), so they used another app which seemed to more reliably give 10-fig refs.
- GPS can accurately tell you it's precision, but not its accuracy. (Yet more confusingly, an ISO standard defines accuracy as 'comprised of trueness and precision' - https://en.wikipedia.org/wiki/Accuracy_and_precision )
- Typical GPS precision on a modern smartphone is
Post edited at 02:27
In reply to PM:
Think I managed to somehow edit the rest of my own post into oblivion. I'm not going to bother typing it a third time; it's clearly not meant to be.
Long story short: I'm pretty skeptical of any app (or GPS for that matter) giving a correct 10-digit OS ref, or even 8-digit in many cases. Luckily I can't think of any situation I'd find myself in where the difference between 6-digit and 8 would be important for me. I think the difficulty of getting 8-digits correct are likely why the OS Locate app only does 6 digits.
Think I managed to somehow edit the rest of my own post into oblivion. I'm not going to bother typing it a third time; it's clearly not meant to be.
Long story short: I'm pretty skeptical of any app (or GPS for that matter) giving a correct 10-digit OS ref, or even 8-digit in many cases. Luckily I can't think of any situation I'd find myself in where the difference between 6-digit and 8 would be important for me. I think the difficulty of getting 8-digits correct are likely why the OS Locate app only does 6 digits.
Post edited at 02:59
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In reply to keith-ratcliffe:
The thread was removed because it was a new first time poster who included a link to a company that she had a connection to.
However the topic of the OS Locate App is a good one hence I have changed the name of this thread so that the discussion on that can continue on here.
Alan
The thread was removed because it was a new first time poster who included a link to a company that she had a connection to.
However the topic of the OS Locate App is a good one hence I have changed the name of this thread so that the discussion on that can continue on here.
Alan
3
In reply to PM:
Was going to download out of curiosity, until I read reviews on the App Store. For this to be in anyway useful it needs to be 100% accurate, which clearly it isn't.
As such, can't help but feel it's potentially dangerous...
Was going to download out of curiosity, until I read reviews on the App Store. For this to be in anyway useful it needs to be 100% accurate, which clearly it isn't.
As such, can't help but feel it's potentially dangerous...
On a straight road you can't tell but sat nav apps position the car at the right place on bends/junctions so they must be routinely as good (both accurate and precise to be pedantic) as an 8 figure grid reference.
1
In reply to plyometrics:
Well, it can't be '100% accurate'. It can only be as accurate as the phone's location information, which itself may be more or less accurate depending on whether it uses the GPS sensor or uses network location ( though apps have the facility to detect this and should warn if this is the case ).
Regarding the Grid Reference itself, this can be calculated using the full OSTN02 polynomial transformation, or the less precise Helmert transformation - which has an error of at most 5 metres. The distinction is moot since OSLocate only gives you a 6 figure reference anyway, though given the app is produced by OS themselves I would assume that they use the more precise transformation.
> Was going to download out of curiosity, until I read reviews on the App Store. For this to be in anyway useful it needs to be 100% accurate, which clearly it isn't.
Well, it can't be '100% accurate'. It can only be as accurate as the phone's location information, which itself may be more or less accurate depending on whether it uses the GPS sensor or uses network location ( though apps have the facility to detect this and should warn if this is the case ).
Regarding the Grid Reference itself, this can be calculated using the full OSTN02 polynomial transformation, or the less precise Helmert transformation - which has an error of at most 5 metres. The distinction is moot since OSLocate only gives you a 6 figure reference anyway, though given the app is produced by OS themselves I would assume that they use the more precise transformation.
2
In reply to elsewhere:
Or use other factors to increase their accuracy, for example my GPS can be set to 'Lock On Road' when being used as a satnav whilst driving. So it assumes you're somewhere on the road, and presumably uses the GPS position along with an algorithm factoring in the speed and direction of travel, to predict where on the road you are.
Or use other factors to increase their accuracy, for example my GPS can be set to 'Lock On Road' when being used as a satnav whilst driving. So it assumes you're somewhere on the road, and presumably uses the GPS position along with an algorithm factoring in the speed and direction of travel, to predict where on the road you are.
1
In reply to elsewhere:
In the case of car sat nav, if it knows where you are roughly, how fast you're going, and that you're on a road, then it can use these three bits of info to put your dot on the road on the map more consistently 'where are are' than by GPS alone.
You can watch it get confused sometimes on motorway slip roads; it has you continuing along the main route, then leaping sideways as it realises you actually took the slip.
In the case of car sat nav, if it knows where you are roughly, how fast you're going, and that you're on a road, then it can use these three bits of info to put your dot on the road on the map more consistently 'where are are' than by GPS alone.
You can watch it get confused sometimes on motorway slip roads; it has you continuing along the main route, then leaping sideways as it realises you actually took the slip.
In reply to PM:
It's not difficult to transform GPS (ie, WGS84) coordinates into OS National Grid. The difficulty is getting the GPS coordinates 'correct' in the first place. In this respect I think that often users have unrealistic expectations.
> I think the difficulty of getting 8-digits correct are likely why the OS Locate app only does 6 digits.
It's not difficult to transform GPS (ie, WGS84) coordinates into OS National Grid. The difficulty is getting the GPS coordinates 'correct' in the first place. In this respect I think that often users have unrealistic expectations.
1
In reply to planetmarshall:
For some values of "not difficult"!
Those who are interested could take a look at http://www.movable-type.co.uk/scripts/latlong-os-gridref.html#datum-convers...
> It's not difficult to transform GPS (ie, WGS84) coordinates into OS National Grid.
For some values of "not difficult"!
Those who are interested could take a look at http://www.movable-type.co.uk/scripts/latlong-os-gridref.html#datum-convers...
2
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In reply to andyjohnson0:
This is the 'Helmert' transform, basically a linear transform of the familiar Mercator Projection. For the UK it's probably accurate enough for most purposes (accurate to about 5 metres), but the problem then is your UK map would require a different scale in the North of Scotland than it would in Cornwall.
OS Maps are produced using an additional polynomial transform called OSTN02 (actually OSTN15 is the latest version), which makes the grid uniform across the whole of the UK. For the gory details see
https://www.ordnancesurvey.co.uk/docs/gps/Updated%20transformations%20for%2...
> For some values of "not difficult"!Those who are interested could take a look at http://www.movable-type.co.uk/scripts/latlong-os-gridref.html#datum-convers...
This is the 'Helmert' transform, basically a linear transform of the familiar Mercator Projection. For the UK it's probably accurate enough for most purposes (accurate to about 5 metres), but the problem then is your UK map would require a different scale in the North of Scotland than it would in Cornwall.
OS Maps are produced using an additional polynomial transform called OSTN02 (actually OSTN15 is the latest version), which makes the grid uniform across the whole of the UK. For the gory details see
https://www.ordnancesurvey.co.uk/docs/gps/Updated%20transformations%20for%2...
In reply to planetmarshall:
Yeah, agreed. What I meant by incorrect 8-figures is using a possibly not accurate-enough position fix as the starting point for calculations.
Regarding the calculations, there was a thread on another forum which I've been unable to find about someone with a GPS which gave identical lat/long position references as another model in the same location, but the OSGB coordinates had a 70m difference between the two units. This seemed to be a 'known problem' with some version of this model, which was presumed to be a problem in the conversion calculation.
Ignoring completely the accuracy/precision issue, if you have a +/- 5m accurate position (by whatever means; GPS, astronavigation, resection), then you have your location inside a 10m wide circle. If you drop that circle onto a map then there's an incredibly slim chance it 100% lies within a 10x10m grid square, and a good chance it covers, two, three or four different grids, any of which you might be in. There's a very good chance that the same 10m circle lies wholly within a 100x100m square, so I'd not have any problems using an app (or GPS for that matter) for a 6-fig reference.
I have a bit more confidence in the OS one than the apps that claim 10-digit accuracy. For the same reasons above, I'd want a 10 centimetre position fix to be able to tell someone a 1m grid with confidence. That said, from playing around with a few apps they do seem to tick over as expected (i.e., walk east, and the 10-digit app's easting goes from 11199 to 11200 at the same place as the OS app goes from 111 to 112).
I'm quite interested in all this as I've been tinkering with writing yet another app that shows OS coordinates. I'm using the 'close enough' Helmert transformation, using the code in the link andyjohnson0 posted. This is currently just for me to play around with, rather than for releasing.
> It's not difficult to transform GPS (ie, WGS84) coordinates into OS National Grid. The difficulty is getting the GPS coordinates 'correct' in the first place.
Yeah, agreed. What I meant by incorrect 8-figures is using a possibly not accurate-enough position fix as the starting point for calculations.
Regarding the calculations, there was a thread on another forum which I've been unable to find about someone with a GPS which gave identical lat/long position references as another model in the same location, but the OSGB coordinates had a 70m difference between the two units. This seemed to be a 'known problem' with some version of this model, which was presumed to be a problem in the conversion calculation.
Ignoring completely the accuracy/precision issue, if you have a +/- 5m accurate position (by whatever means; GPS, astronavigation, resection), then you have your location inside a 10m wide circle. If you drop that circle onto a map then there's an incredibly slim chance it 100% lies within a 10x10m grid square, and a good chance it covers, two, three or four different grids, any of which you might be in. There's a very good chance that the same 10m circle lies wholly within a 100x100m square, so I'd not have any problems using an app (or GPS for that matter) for a 6-fig reference.
I have a bit more confidence in the OS one than the apps that claim 10-digit accuracy. For the same reasons above, I'd want a 10 centimetre position fix to be able to tell someone a 1m grid with confidence. That said, from playing around with a few apps they do seem to tick over as expected (i.e., walk east, and the 10-digit app's easting goes from 11199 to 11200 at the same place as the OS app goes from 111 to 112).
I'm quite interested in all this as I've been tinkering with writing yet another app that shows OS coordinates. I'm using the 'close enough' Helmert transformation, using the code in the link andyjohnson0 posted. This is currently just for me to play around with, rather than for releasing.
1
In reply to plyometrics:
Think it's being outside that's the potentially dangerous bit. I think it's well worth having as a back-up. It's not like it adds weight to your pack. If it doesn't work I'd use something else. Vice-versa, if something else doesn't work, the app might work. If I don't have the app to try, then I might be stuck. I think 100% reliance on any one thing is more dangerous than not getting 100% accuracy from any of several options.
I'd not have any hesitation using any of the apps for a six-figure reference, any more or less than a GPS unit. All the apps I've used have all agreed with each other to the digits displayed, and have matched with where I'd expect them to tick over, when crossing a grid line in an easily identifiable place on a map. None of them (nor the maps, nor your compass, nor the roundness model of the earth etc etc.) are 100% accurate. Luckily nobody needs 100% accuracy.
From reading through some of the recent reviews for OS Locate, one jumped out 'I put my phone on the table and my friend's too and they showed different references'. Sounds to me like 'Our GPS didn't agree with each other while we were using it inside'. I think a little understanding of how it works (or doesn't, in this case) is required to use the app (or GPS) sensibly.
For anyone thinking they need 10-digits, to put things into context, a spot-height dot on a 1:25k map is about 0.3mm wide. This means that dot covers an area of 44 square-metres, so there are 44 10-digit references inside the spot height dot on the map.
> For this to be in anyway useful it needs to be 100% accurate, which clearly it isn't. As such, can't help but feel it's potentially dangerous...
Think it's being outside that's the potentially dangerous bit. I think it's well worth having as a back-up. It's not like it adds weight to your pack. If it doesn't work I'd use something else. Vice-versa, if something else doesn't work, the app might work. If I don't have the app to try, then I might be stuck. I think 100% reliance on any one thing is more dangerous than not getting 100% accuracy from any of several options.
I'd not have any hesitation using any of the apps for a six-figure reference, any more or less than a GPS unit. All the apps I've used have all agreed with each other to the digits displayed, and have matched with where I'd expect them to tick over, when crossing a grid line in an easily identifiable place on a map. None of them (nor the maps, nor your compass, nor the roundness model of the earth etc etc.) are 100% accurate. Luckily nobody needs 100% accuracy.
From reading through some of the recent reviews for OS Locate, one jumped out 'I put my phone on the table and my friend's too and they showed different references'. Sounds to me like 'Our GPS didn't agree with each other while we were using it inside'. I think a little understanding of how it works (or doesn't, in this case) is required to use the app (or GPS) sensibly.
For anyone thinking they need 10-digits, to put things into context, a spot-height dot on a 1:25k map is about 0.3mm wide. This means that dot covers an area of 44 square-metres, so there are 44 10-digit references inside the spot height dot on the map.
4
In reply to PM:
Then, of course, I was in Glen Etive this week, and the OS Locate app (or indeed any GPS-functionality on my phone) didn't work at all. Luckily I was just testing it out, rather than relying on it for navigation.
I think my phone (iPhone 5s) was too cold. Temperature was about 3°C, with a biting 30-40mph wind. Taking it out my pocket for a photo, it was happy taking one. Fully charged in the car, it showed about 50% battery when out on the hill, then switched itself off repeatedly when trying to take any more than one photo.
I suspect the phone may have decided to not even attempt activating the quite power-hungry GPS circuitry, as it sensed that it was fighting to get enough power anyway. Further experimentation to follow on this one I think.
When back in the car, battery was again back up over 80%. Lesson learned!
Then, of course, I was in Glen Etive this week, and the OS Locate app (or indeed any GPS-functionality on my phone) didn't work at all. Luckily I was just testing it out, rather than relying on it for navigation.
I think my phone (iPhone 5s) was too cold. Temperature was about 3°C, with a biting 30-40mph wind. Taking it out my pocket for a photo, it was happy taking one. Fully charged in the car, it showed about 50% battery when out on the hill, then switched itself off repeatedly when trying to take any more than one photo.
I suspect the phone may have decided to not even attempt activating the quite power-hungry GPS circuitry, as it sensed that it was fighting to get enough power anyway. Further experimentation to follow on this one I think.
When back in the car, battery was again back up over 80%. Lesson learned!
1
In reply to Dave the Rave:
When iPhone batteries get very cold they stop working properly, so the lesson is to take a Samsung Galaxy too, because their batteries generate enough heat to get your iPhone working again.
When iPhone batteries get very cold they stop working properly, so the lesson is to take a Samsung Galaxy too, because their batteries generate enough heat to get your iPhone working again.
2
In reply to PM:
I'm sad enough to have checked your maths
That's a really good way of describing the obsession with being totally precise, (and accurate..), I've managed to survive up to now with "I think I'm somewhere within this 100m box. If I walk in that direction away from the huge abyss on the map, (but look where I'm going just in case), for x paces I should pick up a handrail and turn left".
Theres one extreme view that says "USE A MOBILE PHONE IN THE HILLS AND YOU WILL DIE" and another that says "IF YOU HAVE LESS THAN 12 FIGURE PRECISCURACY YOU WILL DIE". It's somewhere between the two.
> I think a little understanding of how it works (or doesn't, in this case) is required to use the app (or GPS) sensibly. For anyone thinking they need 10-digits, to put things into context, a spot-height dot on a 1:25k map is about 0.3mm wide. This means that dot covers an area of 44 square-metres, so there are 44 10-digit references inside the spot height dot on the map.
I'm sad enough to have checked your maths
That's a really good way of describing the obsession with being totally precise, (and accurate..), I've managed to survive up to now with "I think I'm somewhere within this 100m box. If I walk in that direction away from the huge abyss on the map, (but look where I'm going just in case), for x paces I should pick up a handrail and turn left".
Theres one extreme view that says "USE A MOBILE PHONE IN THE HILLS AND YOU WILL DIE" and another that says "IF YOU HAVE LESS THAN 12 FIGURE PRECISCURACY YOU WILL DIE". It's somewhere between the two.
1
In reply to EddInaBox:
Only the note...
> When iPhone batteries get very cold they stop working properly, so the lesson is to take a Samsung Galaxy too, because their batteries generate enough heat to get your iPhone working again.
Only the note...
1
In reply to Dave the Rave:
Yeah, pretty much! Certainly not this particular bit of technology.
> What lesson? Don't rely on technology?
Yeah, pretty much! Certainly not this particular bit of technology.
In reply to Ridge:
Thanks. : )
Agree that there's definitely a happy middle somewhere. Think as I get older I care a bit less about the precision of stuff like this. I don't think that's because I'm More Experienced (whatever that means), but possibly in a bit less of a rush, so spend a bit more time using that other skill you highlight: looking where I'm going.
> I'm sad enough to have checked your maths That's a really good way of describing the obsession with being totally precise, (and accurate..)
Thanks. : )
Agree that there's definitely a happy middle somewhere. Think as I get older I care a bit less about the precision of stuff like this. I don't think that's because I'm More Experienced (whatever that means), but possibly in a bit less of a rush, so spend a bit more time using that other skill you highlight: looking where I'm going.
In reply to keith-ratcliffe:
All the talk in the thread about accuracy is really quite amusing. Any of the transformations are more than good enough to give you a location. Good enough is all you need. Location from compass sightings will often give you a small triangle for location not an exact intersection. But it's more than good enough. I've never bothered with more than 6 digit. My eyesight and fat fingers can cope with that when looking at a map.
All the talk in the thread about accuracy is really quite amusing. Any of the transformations are more than good enough to give you a location. Good enough is all you need. Location from compass sightings will often give you a small triangle for location not an exact intersection. But it's more than good enough. I've never bothered with more than 6 digit. My eyesight and fat fingers can cope with that when looking at a map.
Post edited at 09:43
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