[talk-au] seaward admin boundaries

[Warin]

On 19/1/21 2:50 pm, Andrew Harvey wrote:
>
> On Tue, 19 Jan 2021 at 11:48, cleary <osm at 97k.com 
> <mailto: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.
>
>
> In my opinion, where the boundary is defined by the natural feature 
> (coastline, river, road centerline etc) then the boundary way should 
> be snapped (share nodes) with the natural feature. This provides the 
> most accurate representation and encodes the "defined by the natural 
> boundary" information which would otherwise be lost. As the 
> coastline/river etc changes then the boundaries are kept up to date 
> because they have shared nodes, this is a feature, not a bug.
>
> This is in contrast to your preference cleary. The PSMA and other 
> government datasets aren't the exact boundary definition, only a 
> digital representation of it, if we have a better coastline or river 
> data we should use ours.


OSM data is also not exact. So I don't think claims of OSM being more 
exact than other data is an argument I would make ... considering the 
number of 'inexact' OSM data I come across. And yes I correct it where I 
can.

>
> Of course this is all based on that assumption about what defines the 
> legal boundary, but I doubt it is the GIS files the government and 
> it's 3rd parties (PSMA) produce. Phil's comments seem to backup this 
> claim too.


Looks like the area of NSW that does not conform to the PSMA/DCS Base 
map (I think those are both the same) is simply around Sydney and 
Newcastle  ... so I think I'll change those and be done. All the rest 
looks to use the PSMA data.... which looks to be the low water mark and 
that is not mapped in OSM (yet)... would be difficult to map and given 
the number of contributors willing to map it ... it is never going to be 
done. So you my way of thinking it is the PSMA data that is the way 
forward.

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