On 06/29/2012 09:22 PM, James Umbanhowar wrote:
I have just had a correspondence with another mapper who was remapping
Lake Mead shorelines to match new imagery. Due to a multi-year drought,
Lake Mead and other reservoirs in the west have had significantly
declining water levels. However, the lake levels could increase
dramatically if there were a couple of years of normal/high water.
Alternately, Devil's Lake in North Dakota has had many years of
increasing water levels as the closed basin it drains has had relatively
high precipitation.
The question I have for y'all is do we have any recommendations for how
to map these? For the reservoirs, I think that one could make an
argument for mapping the full level and tagging it with landuse
reservoir (which is rendered as water), but is there any value in
drawing lower lake levels if they persist for many years? Would it be
useful to date the imagery/ survey date used for the shoreline?
Although this answer probably won't help you much, I'd much like to see
it like it is done on some maps with lake Aral, where the 1970's
shoreline is shown in a lightblue outline (and a small text by it). But
that's a renderer thing, and I'm at a loss to find a tag for it.
It could then look something like these two images:
http://www.roalter.it/pub/img/shore-in.png
http://www.roalter.it/pub/img/shore-out.png
As far as I know, with OSM the shoreline should be drawn at the highest
point/high tide (see
http://wiki.openstreetmap.org/wiki/Tag:waterway%3Driverbank, under
Varying water level)
--
Cheers,
Alex
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