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

[Stéphane Henriod]

Hi

I know I am bit insisting (and maybe I'm the only one interested in the
topic?) but what I don't like with the flood_prone = yes is that it is not
easily extensible to other types of hazards (landslides, rockfalls,
avalanches, cyclones...), that are of the highest relevance for many parts
of the world. Am I the only one here who thinks that we should rather try
to promote a model that allows for inclusion of other natural hazards?

This wiki page <http://wiki.openstreetmap.org/wiki/OpenHazardMap> is my
first effort towards this but I am 100% ready to re-think the whole if
someone has a better idea!

And to come back to the initial question, I guess that waterway=riverbank
must be used in almost everycase, to delineate the "normal" extent of the
rivers. Even in areas with huge fluctuations of the water levels, people
are clever enough to build infrastructure where there is *in general* no
water. flood_prone=yes (or any similar tag) should be reserved for extents
bigger than waterway=riverbank (and where, usually, you will find fields,
houses... that might be affected by the high waters).

Cheers,

Stéphane
--
"Le mot progrès n'aura aucun sens tant qu'il y aura des enfants malheureux"
-- Albert Einstein

"A journey does not need reasons. Before long, it proves to be reason
enough in itself. One thinks that one is going to make a journey, yet soon
it is the journey that makes or unmakes you." -- Nicolas Bouvier

Photos de voyages, photos de montagne: http://www.henriod.info



On Sun, Jun 24, 2012 at 7:37 PM, Pierre Béland <infosbelas-gps at yahoo.fr>wrote:

> 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.  See waterway=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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