[talk-au] What do you prefer for Barmah-Millewa: swamp or wood?

[cleary]

You are right to point out that OSM offers a different choice of options compared with the NSW LPI BaseMap. Some time ago, when I couldn't find a legend on the BaseMap, I contacted NSW Spatial Services and I was directed to https://portal.spatial.nsw.gov.au/portal/apps/sites/#/home/pages/map-viewers where the NSW Map is shown with an explanatory legend.

In regard to swamps etc., the BaseMap shows only (1) land subject to inundation, (2) swamp-wet and (3) swamp-dry. I have studied the map and satellite imagery in other parts of NSW and I have visited some areas.  

As you have note, the BaseMap's "swamp-wet" does not differentiate the vegetation in the areas. After studying satellite imagery, I have mapped such areas in which trees are a significant features of the vegetation as natural=wetland + wetland=swamp. However where the vegetation has few or no trees and has more grass-type growth, i have used natural=wetland + wetland=marsh.   

The LPI BaseMap's "land subject to inundation" equates closely with natural=wetland in OSM and "swamp-dry" (seen in drier areas of the state rather than in the Murray River area) seems best mapped in OSM as natural=mud. 





On Tue, 12 May 2020, at 12:13 PM, Little Maps wrote:
> Thanks Michael. Sorry, my last email overlapped with yours. I think a 
> major problem is that the way the LPI Basemap, and folks in Australia 
> generally, use the terms forest, swamp and wetland differs slightly 
> from the way they are described in the OSM wiki pages. For example, the 
> OSM guidelines restrict the term ‘swamp’ to areas with dense trees, 
> whereas the Basemap calls many treeless wetlands ‘swamps’. 
> 
> I initially mapped most of the forest as ‘swamp’ as this followed the 
> OSM wiki page guideline, but wasn’t really happy with this, as I always 
> thought of the place as a ‘flooded forest’ rather than a ‘forested 
> wetland’. Hence my query to the list server. I’ll follow your 
> suggestion below and will change the polygons back to wood in the next 
> day or two, with a ’Wetland’ overlay in most areas to show its 
> seasonally flooded. In practice there won’t be any great precision to 
> the wetland overlay as it’s such a mosaic.
> 
> Thanks again for everyone’s great feedback. Best wishes Ian
> 
> 
> > On 12 May 2020, at 9:55 pm, cleary <osm at 97k.com> wrote:
> > 
> > 
> > One further consideration is that NSW LPI BaseMap shows most of the NSW side of this area as wetland, subject to periodic inundation, while only small areas are shown as swamp.   At the moment, OSM shows most of it as swamp while the named swamps are shown as wetland - exactly the opposite of the LPI BaseMap.  
> > 
> > While the BaseMap is not perfect, it is a reasonably reliable guide in the absence of better information. 
> > 
> > While the BaseMap shows wetland and swamp, it does not show wooded areas. So perhaps the suggestion to show natural=wood and natural=wetland as separate polygons might be a useful approach although I suspect that the two together might then be rendered much the same as natural=swamp.  I too would appreciate other views on this topic. 
> > 
> > 
> > 
> > 
> >> On Tue, 12 May 2020, at 8:37 AM, Little Maps wrote:
> >> Hello everyone, I don’t know if there is any right / wrong answer to 
> >> this question, hence I’m keen to know your preferences...
> >> 
> >> I’m mapping wetlands and vegetation along the Murray River upstream of 
> >> Yarrawonga, and am now mapping in Millewa forest. Millewa (in NSW) and 
> >> Barmah forest (in Vic) support large red gum forests which flood 
> >> regularly. Some areas flood annually, others less frequently. It 
> >> depends on how much water flows down the Murray and which stream 
> >> regulators in the forests are opened or closed.
> >> 
> >> My question is: would it be better to map this as a forest (i.e. 
> >> natural=wood) or as a ‘swamp’, which OSM defines as ‘an area of 
> >> waterlogged forest, with dense vegetation’, tagged as natural=wetland, 
> >> wetland=swamp, seasonal=yes. I’ve read the OSM wiki pages on both 
> >> options.
> >> 
> >> I’ve made a first stab at the area 
> >> https://www.openstreetmap.org/#map=14/-35.8026/145.1484
> >> and have mapped all but the extremes as swamp as this indicates that 
> >> the area floods regularly, which natural:wood does not show. However 
> >> most other areas on the river I’ve come across are mapped as 
> >> natural:wood with relatively small inliers for treeless wetlands and 
> >> some treed swamps.
> >> 
> >> It’s a quick job to change from wetland:swamp to natural:wood and vice 
> >> versa and I don’t hold any strong preferences myself. If the general 
> >> consensus is that the area would be better called a wood (i.e. forest) 
> >> rather than a seasonal wetland I’ll change it immediately.
> >> (I haven’t mapped Barmah forest in Vic, as that was already mapped as 
> >> natural:wood but much of Barmah actually floods even more frequently 
> >> than Millewa).
> >> 
> >> Thanks very much for your advice. Best wishes Ian
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