[talk-au] seaward admin boundaries

Ian Sergeant inas66+osm at gmail.com
Tue Jan 19 04:34:44 UTC 2021


If the "authorative government source" is *right*, then this is all good.

What are the possible cases/issues here?  I can think of a few

1. Accretions and erosion actually change the boundary in real time.  The
boundary is dynamic.
2. Accretions and erosion actually change the boundary - but this only has
administrative effect when the changes are surveyed and updated.
3. The government source is an approximation and doesn't necessarily
correspond to the actual boundary, which is actually administratively
defined by a physical feature.
4. The government source administratively defines the boundary.  Any
correspondence to the physical feature is historical,  or otherwise not
relevant.
5. The government source administratively defines the boundary, but that
data isn't available for us to use, and it seems to closely track a
physical feature which we can use.

If we're certain that OSM data is correct (in cases 1 & 3), I see no reason
to wait for the government authority to correct its data for OSM use it.

If the boundary is the dynamic physical feature, I see no harm is
overloading the physical feature with the boundary relation.

Of course, the actual issue here is more about aligning a physical feature
to the boundary that's approximate in itself (coastline)

Ian.

On Tue, 19 Jan 2021 at 11:48, cleary <osm at 97k.com> wrote:

>
> As with other boundaries, I'd prefer to keep administrative boundaries
> separate from natural features even where they approximate and may once
> have precisely aligned.  I'd like to see administrative boundaries
> consistent with the authoritative government source/s while natural
> features such as rivers, coastline etc. are mapped from satellite imagery.
> Even where coastline erodes or changes in other ways, I think the
> administrative boundaries in OSM should remain unchanged until the relevant
> government authority redraws them.
>
> In regard to high-water and low-water marks, I defer to others with better
> knowledge.
>
>
>
>
> On Tue, 19 Jan 2021, at 8:35 AM, Warin wrote:
> > Hi,
> >
> > Someone has been working on the hi water coastline and that has mucked
> > up the suburban admin boundaries near Sydney. Looking at the DCS Base
> > Map these boundaries look to be further seaward than the hi water mark
> > .. possibly the low water mark, though I have not investigated this. I
> > have roughly moved these admin boundaries to where I think they are
> > according to the DCS Base Map. Certainly this would stop any further
> > problems with edits to the coastline vs the admin boundaries.
> >
> > Personal view: sorta makes sense that the council should have control
> > out to low water mark so they can police it. And would reduce OSM
> > problems with edits of the coastline.
> >
> > Thoughts on legalities, bad idea etc ... ???
> >
> >
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> > Talk-au at openstreetmap.org
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> >
>
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