On 25/01/16 11:58, Ian Sergeant wrote:
Hi,
The road is a vector, representing the road. It does not represent
the road centreline. It has properties, such as width and lanes, and
sidewalks.
If the boundary *is* the physical feature, then it is not corrupting
the data by making it align with the physical feature. If the boundary
is not the physical feature, then don't align it.
How do you know it is the physical feature?
Just because it follows approximately the feature does not mean it is.
When originally gazetted the physical feature may have been located
differently (roads, railways realigned, rivers making new paths) Don't
automatically assume that the feature is still in the same place without
looking at the imagery or physical survey. Don't assume that the
boundary changes to the new position of the road, etc.
The NSW/Victorian border has been done entirely along the riverbank.
Much of it by me and a few others after you guys decided to take your
bat & ball. So, I don't believe this is actually an issue. Do you
have any examples of where this is a concern?
No. It was just an example of were an incorrect assumption had been made.
Tracing the actual border between NSW/Victorian border was actually
quite interesting. You have the gradual accretion or divulsion to
consider, and it is clear the LPI data is not necessarily aligned with
what is current. Most of the border that I've traced I'd consider to
be more current than the LPI data, and I'd certainly want to thrash it
out before someone started replacing it with yet another import. We've
had so much ugliness in the past with these imported data sets with no
follow up.
But the border has not changed the river might have but there is no
change to the border from when it was first surveyed/gazetted. The
border is the line as when gazetted, not as where the riverbank is now.
An example of this is here:
https://www.openstreetmap.org/#map=17/-36.19879/148.03658
Open it in josm then open the nsw imagery, and the nsw basemap and you
can see where the river was originally and where the border runs.
Cheers
Ross
This issue doesn't come up too much with property boundaries - that
are defined independent of the roads. It does come up with rivers and
coastline, and other areas where the physical feature is what is the
boundary.
Ian.
On 25 January 2016 at 11:09, Ross <i...@4x4falcon.com
<mailto:i...@4x4falcon.com>> wrote:
In Australia all property boundaries are not the centreline of the
road there is always a road reserve as Andrew pointed out. So
simple do not make boundaries the road.
Likewise be very careful assuming the boundary is the centreline
of a river. eg the NSW Victoria border along the Murray River.
If you don't know it's actually the southern river bank.
Realistically with these boundaries if you move them to align with
any physical feature then you are corrupting the data. Also if
you make the boundary part of a physical feature without checking
the full length of the boundary then you are corrupting the data
again.
It's really much cleaner and easier to just import/trace the
boundary. If this shows up where a road/railway/whatever should
be then trace it from the imagery as a separate way and tag it
appropriately.
Cheers
Ross
On 25/01/16 08:53, Ian Sergeant wrote:
On 25 January 2016 at 09:29, Andrew Davidson
<u...@internode.on.net <mailto:u...@internode.on.net>> wrote:
The boundaries of the parks and forests are not going to be
roads as they consist of a number of property lots that get
declared for that purpose. Property boundaries don't run down
the middle of the road, they'll be offset (at times the
existing road isn't within the road reserve anymore).
Property boundaries can be rivers (bank or thalweg depending)
or the MHWM (also known as the "coast" in OSM).
If OSM was only a colouring-in exercise, then this would be
straightforward.
However, roads in OSM are a vector representation of the road.
And is is very common for the boundary of an area to be the road
itself, that is there is no small gap between the area and the road.
When the boundary of an area *is* the road, then I think it's
entirely correct to include the ways that make up the road in the
multi-poly that defines the area. Even though the vector nature
of OSM slightly expands features that are 2 dimensional when they
are adjacent to features that are 1 dimensional. The data is correct.
Of course, if the boundary isn't defined by the road, but just
happens to be close to it, then that's different.
Ian.
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