[PROJ] OGC blog post summarising Web-mapping misalignment problem

[Cameron Shorter]

Hi Janne,

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.

Thanks again, Cameron

On 6/9/19 10:44 pm, support at mnspoint.com wrote:
>
> Hello,
>
> 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.
>
> 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.
>
> 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.
>
> A good real life example of that would be:
>
> - 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]
>
> - 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")
>
> - most simple and fastest calculation possible
>
> Janne.
>
> ------------------------------------------------
>
> Cameron Shorter kirjoitti 2019-08-22 00:50:
>
>> Proj folks,
>> 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.)
>> The OGC has published a blog post from us summarising the issues:
>> https://www.opengeospatial.org/blog/3045
>> And we are working on a more detailed discussion paper which we plan 
>> to socialise within a week or two.
>> Cheers,
>> -- 
>> Cameron Shorter
>> Technology Demystifier
>> Open Technologies and Geospatial Consultant
>> M +61 (0) 419 142 254
>
>
> -- 
> MNS Support
> NNS Master Navigator Software
> Copyright © Sapper Oy
> www.mnspoint.com <http://www.mnspoint.com>
> support at mnspoint.com <mailto:support at mnspoint.com>

-- 
Cameron Shorter
Technology Demystifier
Open Technologies and Geospatial Consultant

M +61 (0) 419 142 254

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