Hi Jaakko
The riverbank tag is the one used to establish how the rivers are rendered on
maps. It is suggested to also use the new flood_prone tag to provide
information about flooded zones. But the flood_prone tag is not presently
interpreted by the renderers. Seewaterway=riverbank wiki page
(http://wiki.openstreetmap.org/wiki/Tag:waterway%3Driverbank).
To trace in areas like the Niger river, the ideal situation would be to have
high resolution imagery at various seasons.With the Bing imagery, the portrait
is very different looking at the low and high resolution imageries wich were
probably not taken at the same period. I interpreted the new high resolution
imagery to establish
the riverbank. There are flooded plains that look like rivers with low
resolution imageries. There are old segments of rivers were it is hard to state
using the imagery if water still circulates. Comments about these subjects from
people having local knowledge would be very interesting.
The following Compare map shows a portion of the Niger river that I redrawed
around Gao based on new high resolution Bing Imagery.
http://www.geotribu.net/applications/baselayers/index.php?zoom=12&lon=-0.081845312741164&lat=16.310225072508&l1=mapquest&l2=bingaerial&l3=googlesat&l4=yahoosat
The Mapquest layer shows ther riverbank has it was before I remapped it in
OSM. No islands are traced and the riverbank it shows correspond approximately
to the low
resolution Bing imagery that we see at zoom level 12. The high
resolution Bing Imagery that we see at higher zoom levels gives a
different perspective and make me draw a riverbanks that extends less
then in the original version (select Mapnik layer).
Pierre
>________________________________
> De : Jaakko Helleranta.com <[email protected]>
>À : Pierre Béland <[email protected]>
>Cc : HOT Openstreetmap <[email protected]>
>Envoyé le : Dimanche 24 juin 2012 1h57
>Objet : Re: [HOT] New Bing Imagery in Mali and delimitation of riverbanks
>
>
>Better use the flood_prone=yes (
>http://wiki.openstreetmap.org/wiki/Key:flood_prone ) than riverbank, no?
>
>
>Flood_prone already renders with OUSM, too:
>http://ousm.fr/?zoom=16&lat=18.57912&lon=-72.33423&layers=B000F
>
>
>-Jaakko
>
>
>
>On Sat, Jun 16, 2012 at 11:06 PM, Pierre Béland <[email protected]>
>wrote:
>
>New highres Bing Imagery is available in Mali, at least around Gao in the
>north part along the Niger river. This Imagery let us reconsider where to
>trace the Niger riverbanks. This Imagery was taken at high water and in many
>parts we see flooded farmlands. This brings the question about where should
>we trace the riverbank. If at high water levels, many villages will be in the
>middle of rivers or lakes. For areas like the Niger river, what should be the
>rule?
>>
>>Pierre
>>
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>>
>
>
>
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