Salut dega,
Canvec ne découpe pas la végétation aux routes (entités linéaires). Pour
certaines entités "surface" donc les lacs, en effet, la végétation sera
percée. Ce n'est pas le cas par contre avec les batiments, agglomération...
Je suis d'accord avec les explications de Frank. Je crois que l'OSM est
beaucoup plus qu'une carte qui vise l'utilisation des données spatiales
pour des applications. Si l'OSM n'est qu'une carte alors pourquoi connecter
les segments de routes ? Des segments proches suffirait pour avoir une
belle carte ! Mais à quoi servirait le réseau routier pour des applications
de navigation.
En suivant les directives documentées pour le chargement de Canvec, Canvec
reste une source utile pour les régions non cartographiées et
complémentaire pour les régions où il existe des contributeurs OSM.
Cheers,
Michel
On Wed Nov 19 2014 at 7:39:16 PM Ga Delap <gade...@gmail.com> wrote:
> Salut Frank, long time no see
> > ... What if you get an extract of OSM, and you're only
> > interested in the forests, because you want to calculate the percentage
> > of forest coverage. You don't get information about lakes, heath and
> > other land uses when you don't cut out holes from multipolygons.
> You're right but that's a moot point.
> From my point of view, OSM is not a tool for GIS professionals. It's a
> community project ("activité citoyenne"). From a scientific and rigorous
> perspective, a forest must have a hole for any 2D entity (lake, river,
> road,
> street and building). But, if you go that way, editing the map will become
> so
> complex (or arduous as you say) that no normal contributor will be
> interested
> any more.
>
> Look at this "monstruous" way:
> http://openstreetmap.org/way/175486790
> It's a CanVec import with 1420 nodes, part of relation 2344036.
> The way was imported after many of the streets have been created. So the
> forest is "on top" of streets and roads and there's no hole for them.
> Do you really think a human being will get satisfaction and pride if he/she
> have to dig holes around every street?
> And look at the above example. The golf course is on top of the forest
> (without a hole) albeit it has a significant area.
>
> It the goal is to use the OSM database as a rigorous GIS ressource, then
> the
> tools designed for humans (Id, Potlatch, JOSM) will have to be modified to
> automatically create a hole around any 2D object. If they are not
> modified, you
> may say goodbye to normal contributors.
>
> You may also broadcast this message to Europe because the first european
> forest
> I looked at do not have holes for lake, rivers and roads.
> http://www.openstreetmap.org/#map=15/52.1965/-3.8386
>
> Regards,
>
> dega
>
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