[HOT] Re : New Bing Imagery in Mali and delimitation of riverbanks

Pierre Béland infosbelas-gps at yahoo.fr
Sun Jun 24 18:37:11 BST 2012


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 <jaakko at helleranta.com>
>À : Pierre Béland <infosbelas-gps at yahoo.fr> 
>Cc : HOT Openstreetmap <hot at openstreetmap.org> 
>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 <infosbelas-gps at yahoo.fr> 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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