Re: [talk-au] National Park unclosed poly, want advice

[Nathanael Coyne]

Thanks Paul, I'll see if that's an option, especially as it's not a named
forest.

Now I've also got this situation where the much larger but very low
fidelity forest poly is conflicting with my new high-fidelity poly for the
actual Murramarang National Park

https://www.openstreetmap.org/#map=14/-35.6942/150.2560

I don't know whether to clean up the edge of the larger forest poly to use
the same coastline nodes as my national park poly because there's also the
issue that the national park probably can't be considered a subset of the
forest poly as there are non-forest regions within the national park!



Nathanael Coyne (Boehm)

www.purecaffeine.com

Canberra, Australia
0431 698 580

On 22 April 2015 at 05:41, Paul Norman penor...@mac.com wrote:

 On 4/18/2015 11:35 PM, Nathanael Coyne wrote:

 I'd appreciate if someone could have a look at it and tell me if it is
 valid or invalid and if invalid then where I should start with fixing it
 up, given it covers such a large area.

 http://www.openstreetmap.org/way/204064026#map=10/-35.8657/150.1611

 The way itself isn't a polygon, but is part of the multipolygon
 http://www.openstreetmap.org/relation/1388357

 It is valid, but an area this large is a problem to deal with for a number
 of reasons
 - You're more likely to conflict with people editing it
 - Checking validity is hard, as you need the entire  polygon
 - It poses problems for rendering toolchains

 Coming from an area with many areas of trees, I have a few techniques. One
 is to end up splitting on an arbitrary line. While this fixes the problems,
 it's not ideal. A better route is to find an appropriate break in the trees.

 Typically along roads, rivers, power lines, and oil and gas lines there is
 a break in the trees. I try to find one and trace this break. This also
 tends to find clearings (
 https://www.openstreetmap.org/#map=15/-35.8707/149.9854), unmapped roads
 branching off, and other features of interest.

 Don't feel you need to be perfect, particularly in a case like this where
 the original tracing is from landsat.


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Re: [talk-au] National Park unclosed poly, want advice

[Andrew Harvey]

On 22 April 2015 at 06:23, Nathanael Coyne n...@purecaffeine.com wrote:
 Now I've also got this situation where the much larger but very low fidelity
 forest poly is conflicting with my new high-fidelity poly for the actual
 Murramarang National Park

 https://www.openstreetmap.org/#map=14/-35.6942/150.2560

 I don't know whether to clean up the edge of the larger forest poly to use
 the same coastline nodes as my national park poly because there's also the
 issue that the national park probably can't be considered a subset of the
 forest poly as there are non-forest regions within the national park!

As you've noted the National Park Boundary isn't going to always be
natural=wood, so maybe keeping them in separate ways/multipolygons is
best? Regarding the coastline, does the NP boundary extend to the
coastline? Do the trees also extend that far? Normally you would get
some rock or sand between the trees and the coastline, so they
probably won't match up. It depends how much detail you want to put
into it.

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Re: [talk-au] National Park unclosed poly, want advice

[Bryce Nesbitt]

Forest polygons are generally understood to not be very precise.  And the
treeline changes over time anyway.
Do don't bother to make those align.

I do like to see edges of water and lakes matching up with the park
poloygons, otherwise
you end up with lots of strange color bands on rendered maps that seem to,
but don't actually,
have semantic meaning.   Some people share nodes to make the match
perfect.  Others find that annoying to edit.

To share nodes in JOSM click on two nodes and select join.
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