[OSM-talk] What does WGS84 mean for openstreetmap these days?

Greg Troxel gdt at lexort.com
Thu Dec 19 17:51:48 UTC 2019


Simon Poole <simon at poole.ch> writes:

> Thus is a slightly tricky subject and it is not going away.
>
> For another aspect of it see
> https://www.openstreetmap.org/user/StephaneP/diary/390290

Thanks -- I had not seen that.

I would say that to be pedantic, there is a minor error in the post, in
that OSM coordinates are by definition WGS84.  Agreed that when people
add points with coordinates that are in other datums, then the points in
the database have errors.

I am in the process of figuring out how to deal with this, as accurate
locations in my state basically come from using the state's reference
network, which gets you NAD83(2011) epoch 2010.0.

> Essentially in some cases we are using imagery that isn't actually using
> WGS84 as if it was (fsvo of WGS84 as you correctly point out) and we
> currently don't actually have a way to correct this . And yes while
> continental shift is for most countries smaller than all the other ones
> when adding geometry, for Australia this not necessarily true.

That's true for how people with editors generate coordinates.  It seems
quite possible to adjust imagery to WGS(G1762) in editors, and arguably
that should happen.  I wonder though how often imagery is sufficiently
accurate in some national datum that this matters.  I suspect it's more
and more often.


In my message, was really trying to deal with the issue that by saying
"WGS84" instead of "WGS84(current realization)", OSM has a built-in
uncertainty of about 2m before we even start talking about where data
came from.  That seems easy to take off the table with zero workflow
changes.  At least then there will be a clear definition of what's
intended.

Actually changing the notions is much more difficult and I was trying to
separate the easy step from the harder ones.




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