[Talk-GB] accurate GPS

Jez Nicholson jez.nicholson at gmail.com
Wed Oct 9 14:09:53 UTC 2019

BTW if you have any details to add on the relevance of trig points to OSM
then please do add to

On Wed, Oct 9, 2019 at 2:41 PM Simon Ritchie <simonritchie.uk at gmail.com>

> 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 this forum, or some of them,
> and surveyors and architects, of course.  There's also archaeologists,
> because they are required to log where they find objects, and they use GPS
> trackers to do it.  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.
> They would only have to dig a small hole to find it.
> I note your point about plate techtonics.   My local archaeology group
> recently re-excavated a site that was first excavated a hundred years
> earlier.  The records they had turned out to be quite misleading.  That was
> due to poor record keeping, but I guess over that time, the UK might have
> moved around a bit.  I recall that one end is rising and the other is
> sinking.
> However, when new equipment comes along, people find new uses for it.  We
> moved house a few years ago and I saw our Land Registry documents.  I was
> quite surprised at the rudimentary map that is the legal definition of our
> property.  I'm supposed to resolve a boundary dispute with this? Now that
> land is so valuable, I can see people demanding better, so the estate agent
> will walk around the boundary with a GPS device and the result will be
> logged with your land registry records.
> In the future I can also see architects putting GPS coordinates on plans,
> and builders using accurate GPS devices to do the initial  layout of the
> site.  At 2 cm accuracy, they will probably have to tweak the positions
> using better instruments, but if GPS speeds up the process or makes it more
> reliable, they will use it.
> .
>> Relative accuracy (i.e. consistency of measured points
>> within a reasonably sized area) is much easier to achieve than
>> absolute accuracy (which is not even an especially well-defined
>> concept in this case).
> Given the inaccuracy of the trig point locations, I can't even do that :(
> Regards, Simon
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