On Tuesday 17 February 2015, malenki wrote: > > > >10000 ways each with 2000 nodes would be 20 million nodes. Evenly > >distributed on 14000 km outline means a node distance of 70cm - your > >average node distance seems to be more in the range of 10-20m - i > >suppose something is wrong here, for comparison the world coastline > > is only 33 million nodes. > > A subset of 92.331 km I just looked at has 8,764 nodes. That is not > too much imho. You should take into consideration that there are also > some islands which are responsible for the big growth in the count of > members.
Yes - my mistake, you probably don't get an average way size of more than about 50 nodes - that would bring you to about 500k nodes with 10k ways. > I am aware of this and not too lucky about it. > The shape existing until my updates started I created in 2009 with > Landsat Imagery. Then it had 8000 km length and was quite rough. > For curiosity I had a look at the first version of Lake Nasser – the > shore was 1733 km long. > > >There currently is no established rule what water level to map > >as natural=water in such a case (average/maximum/minimum) or how to > >tag separate mappings of different levels. In any case you might > > want to consider that mapping both the minimum and maximum based on > > lower resolution data (like Landsat images) would be ultimately > > more useful than mapping a fairly undefined in-between state in > > higher resolution. > > Imho the minimum would be empty ;) Not really - a typical reservoir cannot be fully emptied. There usually is a normal operational range of water levels which can of course also change over time. The old legacy Landsat images from 1999-2003 you can see on Bing and Mapbox Satellite at low zooms and which are probably the basis of the old mapping generally show a very high water level for Lake Nasser, probably close to the operational maximum. The normal seasonal variation of recent years can be well seen on and could be mapped from Landsat 8 images - like: http://earthexplorer.usgs.gov/metadata/4923/LC81740442014188LGN00/ http://earthexplorer.usgs.gov/metadata/4923/LC81740442015047LGN00/ -- Christoph Hormann http://www.imagico.de/ _______________________________________________ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
