Hi, You can do it with open source tools with the gdistance package from R. Start with this: http://cran.r-project.org/web/packages/gdistance/vignettes/gdistance-vignette.pdf
(from this page: http://cran.r-project.org/web/packages/gdistance/index.html ) You can use the QGIS ManageR plugin to import easily geo data into R. I would do it this way: Take the OSM coastline (you need a polygon). Rasterize it (0=ocean, 1=earth). Import this into R (use the raster package). Define a full conductivity for earth and zero conductivity for water. The rest is straightforward (cf. gdistance-vignette.pdf pp. 12-15). There is a full example for a very similar application (here, the cost is related to sloppy terrain, not water; water is simpler as it is binary). You can use R alone or with QGIS. I suggest you read the first 10 pages of one of the "Documents with fewer than 100 pages" at http://cran.r-project.org/other-docs.html It should be enough to understand the gdistance-vignette.pdf Hope this helps, Mayeul Le mardi 14 juin 2011 à 21:13 +0200, Iván Sánchez Ortega a écrit : > On Martes 14 Junio 2011 17:52:08 Ævar Arnfjörð Bjarmason escribió: > > The routing libraries I've found seem to all assume that I want to > > route across roads, whereas for this task all I need is just a > > coastline shapfile of the planet. I'd then find out if A and B are on > > different coastlines, or the shortest path between them on land. > > > > Is there anything that does this already? > > The thing you want is called a "navigation mesh". You might want to search > for > libraries to make and transverse them. > > Do read: > > http://theory.stanford.edu/~amitp/GameProgramming/MapRepresentations.html > > > Cheers, _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
