Re: [talk-au] Why set coast line to nation park or, administrative boundaries?
On Wed, 29 Mar 2023 at 14:05, OSM via Talk-au wrote: > Since the coastline tag is also supposed to represent the high water mark > then I would say that they should be snapped together (since they then > represent the same feature - that is, the high water mark). This would mean > that the boundary data already in OSM from the government basemaps would > just be their own mapping of the high water mark, and probably be less up > to date or refined as our own. > Exactly. So if anything we should be actively snapping them. > This is my first time responding on talk-au, lmk if I've messed up any > formatting to link to the original question. > It's come through but as a new thread, and for some reason from talk-au instead of from you and via talk-au. ___ Talk-au mailing list Talk-au@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Why set coast line to nation park or, administrative boundaries?
I looked at the separation of park boundaries and coastlines down in Wilson's Prom a while ago and asked the #oceania discord at the time but never ended up changing anything. If you look at the legal definition of many national parks, their boundaries are defined by the high water mark. Since the coastline tag is also supposed to represent the high water mark then I would say that they should be snapped together (since they then represent the same feature - that is, the high water mark). This would mean that the boundary data already in OSM from the government basemaps would just be their own mapping of the high water mark, and probably be less up to date or refined as our own. The other issue I wasn't sure about was the copyright of the government maps that declare these national parks as following the high water mark. You could argue that its a legal fact and therefore can't be copyrighted but it is also hard to find that information outside of government run archives. (The parks are usually represented on maps of the area by the Surveyor General and make references to the high water mark, at least in Vic). This is my first time responding on talk-au, lmk if I've messed up any formatting to link to the original question. On Tue, 28 Mar 2023, at 10:58 AM, Warin wrote: Hi Looks like some are setting natural features to government boundaries. A recent case along the WA south coast has been going on for some years.. The coast line looks very confused and the National Park boundaries are being changed to the coast line in reverse of what is stated on the change sets... (bangs head on wall). I was altered to it by OSMInspector identifying the National Park boundary being broken by the 'adjustment' of the 'coastline' ... that broke the National Park boundary... The National Park boundary looks, in some places, to be the low tide mark and then in other places to be the hi tide mark, so it is not consistent. I do understand where the two (natural feature and government boundary) coincide that it is easier to use the same way. But every now and then someone moves it to conform to the latest imagery of the natural feature .. thus moving the government boundary .. unintended but there we go. My only solution si to have them as separate ways .. making it easier to divorce the new nodes added for the new nature feature addition from the old government boundary. Any other ideas??? ___ Talk-au mailing list Talk-au@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-au___ Talk-au mailing list Talk-au@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Why set coast line to nation park or administrative boundaries?
Slightly different issue… but the accuracy of governmental admin boundaries can vary a lot depending where you are in Aus. In regional NSW, allotment boundaries (and associated park, state forest and local gov boundaries) as shown on the NSW gov base map (and as often used in OSM) are often inaccurate by 20-50 m and sometimes lots more. This inaccuracy is clearly stated on the Six Maps FAQ page (see Q 6&7). https://www.spatial.nsw.gov.au/__data/assets/pdf_file/0005/216383/SIXMapsFAQ.pdf Basically, this statewide dataset is not intended to be used at the high zoom levels that we can use in OSM. Personally, I’d echo Frederick and Andrew’s view that we may be seeking a false sense of exactitude by focusing on small apparent differences between statewide datasets and natural features. Cheers Ian___ Talk-au mailing list Talk-au@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Why set coast line to nation park or administrative boundaries?
Personally I'd prefer to snap them, it makes it easier for us to maintain, better for data consumers, and overall cleaner data. I speculate these departmental GIS teams are creating the boundaries from their own coastline datasets anyway, so why not just have them match OSM's coastline? I think it's unlikely these GIS representations are the absolute set in stone authority, if they rebuild their GIS data with newer coastline data their boundary geometry will change. I agree with Frederik here, if someone wants the boundaries exactly as they appear in the government published dataset they should go there and not expect OSM to be exactly the same. They shouldn't be untouchable objects in OSM, we can hold a different representation of the boundary to the department's GIS dataset that doesn't make OSM wrong. I think you'll find exactly what Frederik says, that the moment you step foot on the land out of the water you'll be deemed in the national park for most purposes, except particular cases where the boundaries does extend out in the water. > ___ Talk-au mailing list Talk-au@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Why set coast line to nation park or administrative boundaries?
Hi, I would advise caution with this. Government bodies will typically hold their own GIS data for park boundaries or administrative boundaries, and the GIS data they have will never fully align with the coastline. However, it is not our job to be an agent for publishing government data. We have to look further and ask for the actual situation. If the national park boundary is mostly along the coastline but there's a tiny patch of sand where the coastline has changed but the public data has not - does that really mean that this little patch is not part of the national park (and I could go there and, whatever, light a fire or something I'm not allowed to do in the national park)? OpenStreetMap becomes more complex the more different boundaries we track. Having a coastline with an administrative boundary that runs "almost" along the coast but is always a meter off, and then having in addition to that a national park boundary that is also "almost" the same but not quite - we should only do that if it is an important feature. "Hey, everyone knows that along the coast of XY there's this one meter wide stretch that is not officially part of the XY city so the city rule about nude bathing doesn't apply there" or whatever, that might be a reason to carefully map the difference - but if the difference is not "on purpose" but just an imprecision that the city and national park administration were likely to fix if they had the technical means then I would not try to map these boundaries separate from the coastline. Especially since they will certainly not be verifiable on the ground... Bye Frederik On 28.03.23 11:33, cleary wrote: Warin's proposal, that natural features be separated from administrative boundaries, is strongly supported. Boundaries are often near natural features but they rarely align precisely. Further, natural features such as coastline and waterways can change surprisingly quickly while administrative boundaries change much less often. On Tue, 28 Mar 2023, at 10:58 AM, Warin wrote: Hi Looks like some are setting natural features to government boundaries. A recent case along the WA south coast has been going on for some years.. The coast line looks very confused and the National Park boundaries are being changed to the coast line in reverse of what is stated on the change sets... (bangs head on wall). I was altered to it by OSMInspector identifying the National Park boundary being broken by the 'adjustment' of the 'coastline' ... that broke the National Park boundary... The National Park boundary looks, in some places, to be the low tide mark and then in other places to be the hi tide mark, so it is not consistent. I do understand where the two (natural feature and government boundary) coincide that it is easier to use the same way. But every now and then someone moves it to conform to the latest imagery of the natural feature .. thus moving the government boundary .. unintended but there we go. My only solution si to have them as separate ways .. making it easier to divorce the new nodes added for the new nature feature addition from the old government boundary. Any other ideas??? ___ Talk-au mailing list Talk-au@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-au ___ Talk-au mailing list Talk-au@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-au -- Frederik Ramm ## eMail frede...@remote.org ## N49°00'09" E008°23'33" ___ Talk-au mailing list Talk-au@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-au
