<div dir="ltr">To add more challenges to this issue is <a href="https://wiki.openstreetmap.org/wiki/Imagery_Offset_Database">imagery offset</a>. The value can even be varied from tiles to tiles, that we often need to shift the object a couple of meters away. In a remote area, where there are no GPS traces as a reference, satellite imagery is often the only reference even when possibly it was a couple of meters off. <div><br></div><div>Best,</div><div>Iyan</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Dec 20, 2019 at 12:59 AM Greg Troxel <<a href="mailto:gdt@lexort.com">gdt@lexort.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">"Jóhannes Birgir Jensson" <<a href="mailto:joi@betra.is" target="_blank">joi@betra.is</a>> writes:<br>
<br>
> I don't think we can or will be providing accuracy up to cm when most<br>
> of the stuff we map from our chairs is off by a meter or two anyways -<br>
> the beauty is that it doesn't matter for 99,99% of users. If a<br>
> centimeter matters then we are probably dealing with legal matters and<br>
> there OSM makes it quite clear it is not suitable for such.<br>
<br>
My actual proposal, as opposed to the things I pointed out I wasn't<br>
proposing, is about removing the ~2m uncertainty that exists from our<br>
current definition.<br>
<br>
As for cm level, OSM does not have accuracy specifications and won't.<br>
Some people like to be accurate, and others like to add lots of detailed<br>
tags. Between us we have great map. I don't agree that anybody who is<br>
trying to be more accurate is necessarily concerned with something that<br>
is "legal". I would expect many people would like to see better than 2m<br>
accuracy.<br>
<br>
Certainly cm-level is very difficult, and I see that as being pretty far<br>
out in the future.<br>
<br>
You didn't comment on the notion of defuzzing the reference to WGS84, so<br>
I'll assume you are ok with that.<br>
<br>
> Also regarding the accuracy, as another fast moving country Iceland is<br>
> actually splitting in the middle and so it edges west and east and<br>
> south as well, depending on where you are in the country. We've had 3<br>
> official national datums now, ISN93, ISN2004 and ISN2016 (helpfully<br>
> naming them after years). The fact is that pretty much everything is<br>
> still running in ISN93, ISN2004 saw very little uptake and ISN2016 has<br>
> started very slowly.<br>
><br>
> So for Iceland we do know that we are never going to achieve a<br>
> centimeter accuracy, pretty much ever, and don't expect a free people<br>
> sourced geographical database to reach it.<br>
<br>
Interesting about the datum history. But this is the cm strawman I<br>
wasn't talking about, not the 2m issue.<br>
<br>
I would not be surprised if in 20 years OSM had some approach to<br>
coordinates of crust-fixed points.<br>
<br>
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</blockquote></div>