On 10/10/19 00:40, Simon Ritchie wrote:
The real question, really, is why you're aiming for that level of
precision
That's what the emerging equipment does.
For 'precision' i.e. repeatability then simply monitor the indicated
position over a short time frame - where the satellites
Oh, is /that/ what he's doing?
On 10/10/2019 17:47, Jez Nicholson wrote:
*Ahem* no offence to Simon, obviouslyhe's just trying to check out a
manufacturer's claims and opening a can of worms in the process.
On Thu, Oct 10, 2019 at 5:18 PM Dave F via Talk-GB <
talk-gb@openstreetmap.org>
*Ahem* no offence to Simon, obviouslyhe's just trying to check out a
manufacturer's claims and opening a can of worms in the process.
On Thu, Oct 10, 2019 at 5:18 PM Dave F via Talk-GB <
talk-gb@openstreetmap.org> wrote:
> On 09/10/2019 23:12, Warin wrote:
> >
> > I'd think to get that level
On 09/10/2019 23:12, Warin wrote:
I'd think to get that level of accuracy you 'd need readings over some
considerable time... days?
Otherwise you get bias from, as you hint, the atmospheric conditions,
the satellites in view - their bias, angles ..
Unless you have access to correction
On 09/10/19 22:57, Simon Ritchie wrote:
> You'll need a GPS receiver with the capability of outputting carrier
phase data (u-blox receivers will do this) and ideally a
well-characterised external antenna (these are quite expensive).
That's very useful. Thanks. I am indeed using a uBlox
On 09/10/19 22:03, Dave F via Talk-GB wrote:
2cm? I'm intrigued, what model are you using?
What were the atmospheric conditions on the day you took your reading?
I'd think to get that level of accuracy you 'd need readings over some
considerable time... days?
Otherwise you get bias from, as
On 09/10/19 22:42, Peter Neale via Talk-GB wrote:
... and if you had 2 devices, how would you know which is right? You
would need at least 3 devices, so that you could take a majority vote.
Actually 5 would better
6 is general taken as a minimum number to get a good student's T
And they
On 09/10/2019 14:40, Simon Ritchie wrote:
They often leave objects in the ground to protect them, and then come
back a few years later to have another look using new techniques. It
would be nice if they knew precisely where their target is.
For that, you really need to record one or more
BTW if you have any details to add on the relevance of trig points to OSM
then please do add to
https://wiki.openstreetmap.org/wiki/Ordnance_Survey_triangulation_stations
On Wed, Oct 9, 2019 at 2:41 PM Simon Ritchie
wrote:
> The real question, really, is why you're aiming for that level of
>
> The real question, really, is why you're aiming for that level of precision
That's what the emerging equipment does. I'm just planning on showing how
it can be put together, but I'd like to be able to say with confidence that
it works properly.
As to who will use it, there's the readers of
On Wed, 9 Oct 2019 at 12:57, Simon Ritchie wrote:
> However, that still leaves the fundamental problem: I can (and will)
> publish the kit of parts for making your own base station. You could use
> something similar to build a rover or you could buy one off the shelf.
> According to the
> You'll need a GPS receiver with the capability of outputting carrier
phase data (u-blox receivers will do this) and ideally a well-characterised
external antenna (these are quite expensive).
That's very useful. Thanks. I am indeed using a uBlox device as my base
station. I ran it for 48
today,
even if the measurements nowadays are generally completed using GPS.
Cheers
Andy
From: Simon Ritchie [mailto:simonritchie...@gmail.com]
Sent: 09 October 2019 12:32
To: Russ Garrett
Cc: Talk GB
Subject: Re: [Talk-GB] accurate GPS
> You're not going to find a (publica
On Wed, 9 Oct 2019 at 12:31, Simon Ritchie wrote:
> > You're not going to find a (publically-accessible) physical location which
> > has better location error than 1m or so.
> That was the kind of conclusion that I was coming to. There's the meridian
> line at Greenwich, but that only gives
... and if you had 2 devices, how would you know which is right? You would need
at least 3 devices, so that you could take a majority vote.
Actually 5 would better
Or 7, or 9
Peter
Sent from Yahoo Mail on Android
On Wed, 9 Oct 2019 at 12:34, Simon Ritchie wrote:
> You're not going to find a (publically-accessible) physical location
which has better location error than 1m or so.
That was the kind of conclusion that I was coming to. There's the meridian
line at Greenwich, but that only gives one coordinate. It's a pity that
they don't have a crosshair
On Wed, Oct 09, 2019 at 11:49:35AM +0100, Russ Garrett wrote:
> On Wed, 9 Oct 2019 at 11:40, Andy Robinson wrote:
> > Are you using trig points that are also OS Net station locations?
> > https://www.ordnancesurvey.co.uk/legacy/docs/gps/OSNet_GPSWebSite_Coordinates_File.txt
>
> Pretty sure that
I believe that the original data from the OS is completetrigarchive.zip.
Ian Harris created the trigpointing .uk website from that. The map
references for the three trig points I used are from that website, and yes,
you can walk up to those trig points and plonk your GPS device onto them.
The
2cm? I'm intrigued, what model are you using?
What were the atmospheric conditions on the day you took your reading?
DaveF
On 09/10/2019 11:05, Simon Ritchie wrote:
I've been working with some GPS equipment that claims to be accurate to
2cm. To test it, I've been visiting local OS trig
On Wed, 9 Oct 2019 at 11:47, Gareth L wrote:
> Are you including the continental drift? That will make etrs89 gps coords be
> about 60-70cm off by now
That's the total net error since ETRS was established, but the ETRS
reference frame moves with the Eurasian plate and corrections are
issued, so
You are entering an extremely deep rabbit hole here and there are
hundreds of extremely nerdy aspects you have to consider when aiming
for sub-metre precision.
As you correctly point out, the position of trig points is no longer
accurate nor canonical. Errors of half a metre sound absolutely
On Wed, 9 Oct 2019 at 11:40, Andy Robinson wrote:
> Are you using trig points that are also OS Net station locations?
> https://www.ordnancesurvey.co.uk/legacy/docs/gps/OSNet_GPSWebSite_Coordinates_File.txt
Pretty sure that all those OS Net locations are actually fixed GPS
receivers rather than
Are you including the continental drift? That will make etrs89 gps coords be
about 60-70cm off by now
On 9 Oct 2019, at 11:06, Simon Ritchie
mailto:simonritchie...@gmail.com>> wrote:
I've been working with some GPS equipment that claims to be accurate to 2cm.
To test it, I've been visiting
[mailto:simonritchie...@gmail.com]
Sent: 09 October 2019 11:06
To: talk-gb@openstreetmap.org
Subject: [Talk-GB] accurate GPS
I've been working with some GPS equipment that claims to be accurate to 2cm.
To test it, I've been visiting local OS trig points, taking position
measurements and checking
I've been working with some GPS equipment that claims to be accurate to
2cm. To test it, I've been visiting local OS trig points, taking position
measurements and checking if they are correct.
Unfortunately I've discovered that the data I'm getting from the OS is not
nearly as accurate as my
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