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<p>Hi Janne,</p>
<p>Thanks for your suggestions. As I understand it, you are
suggesting take the simple approach, which is "near enough" and
don't worry about accounting for tectonic plate movement. This is
the approach that has been used in web-mapping to date. In
Australia, we are discovering that that this approach is not "good
enough" anymore. Australia is on the fastest moving tectonic
plate, moving at 7cm per year, a point on our national static
datum (from 1994) is ~ 1.8 out from to where a GPS receiver says
it should be. This inaccuracy is not good enough for many of
modern mapping's emerging use cases. Hence this week's
conversations at the OGC technical committee meeting will be
around options for improving accuracy.</p>
<p>Thanks again, Cameron<br>
</p>
<div class="moz-cite-prefix">On 6/9/19 10:44 pm,
<a class="moz-txt-link-abbreviated" href="mailto:support@mnspoint.com">support@mnspoint.com</a> wrote:<br>
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<p>Hello,</p>
<p>in the name of simplicity I would suggest storing and
referencing data to "what the most simple GPS (GNSS) receiver
gives" if possible ... and without any additional datum or
ellipsoid or time (outside GMT(UTC) or geoid transformations.
Since GPS receivers usually give accurate time and (temporary)
coordinate information BUT often cannot even calculate the geoid
correctly (so better to use the reference ellipsoid instead). So
anything too complicated from the GPS receiver is out of the
question ... and would also slow down the process needlessly
when recording lot of points.</p>
<p>And since that would be the preferred way to store data ... and
what also could stay reasonably accurate at least year or two
everywhere on the planet (forgetting the time) which usually
suits most needs. And then the rest of the complexity built on
that and starting from there.</p>
<p>If one needs to know wehere the point really was since it is
now maybe 50 years since it was measured he would then do some
more (but minimal) complicated calculations.</p>
<p>A good real life example of that would be:</p>
<p>- the beginning of some Australian runway was recorded "here"
(coordinates and time using some simple GPS receiver) 50 years
ago [additionally maybe its length, direction and slope]</p>
<p>- where it is now (coordinates directly usable with some simple
GPS receiver .. so to be able to ask "where should I go now to
find the same spot")</p>
<p>- most simple and fastest calculation possible</p>
<p>Janne.</p>
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<p>Cameron Shorter kirjoitti 2019-08-22 00:50:</p>
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<div dir="ltr">Proj folks,
<div>A bit of an update. A few of us have been refining our
thinking and description of the web-mapping misalignment
problem. Scott from the OGC has noted the importance of this
topic and invited us to raise the topics at the next OGC
Technical Committee meeting at Banff (9 Sept). (Getting
approval to travel to the event is becoming trickier than
we'd expected.)</div>
<div> </div>
<div>The OGC has published a blog post from us summarising the
issues:</div>
<div><a href="https://www.opengeospatial.org/blog/3045"
target="_blank" rel="noopener noreferrer"
moz-do-not-send="true">https://www.opengeospatial.org/blog/3045</a></div>
<div> </div>
<div>And we are working on a more detailed discussion paper
which we plan to socialise within a week or two.</div>
<div> </div>
<div>
<div>Cheers, </div>
-- <br>
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<div><span style="font-size: 12.8px;">Cameron
Shorter</span></div>
<div>Technology Demystifier</div>
<div>Open Technologies and Geospatial
Consultant</div>
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<div>M +61 (0) 419 142 254</div>
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<p><br>
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<div>-- <br>
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<pre class="moz-signature" cols="72">--
Cameron Shorter
Technology Demystifier
Open Technologies and Geospatial Consultant
M +61 (0) 419 142 254</pre>
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