Hi, 2009/12/31 <srmix...@hotmail.com>: > The state of California has some good landcover shapefiles on the > Department of Forestry and Fire Protection site. They are sorted by > county. The smallest are under a meg while the largest - Fresno - is more > than 400 megs. The average size is around 30 to 40 megs. These would be a > great addition to OSM since they contain valuable metadata. Once the > areas have been added, the state will take on a similar look to states > like Georgia and Massachusetts that have > had statewide imports done. Another good example of what California can > be is the Corine Land Cover (WikiProject Corine Land Cover). > > There are several challenges with the data. Here are a couple. > * It is a huge dataset and will need some optimization. The straight > lines have points every five meters, creating jagged edges that > aren't visually attractive. Josm has a plugin but that's probably not > the best way. A spline interpolation would really improve it > dramatically. It will increase data size, but it's worth it. Maybe > there is a batch mode program available to do that. Mapshaper has a > tool to optimize a shapefile by reducing the details in the file. It > may not be working though. Here is a rough idea of what the areas > look like without being simplified. > > * Only vegetation data should be used. The > urban/residential/water/unknown should be skipped since the quality > isn't good enough for this purpose and would just create tons of > conflicts with existing data. Also there is/will be better data > available. > > * We can use some filters to split the shapefiles into different > features. This is also great to prepare the OSM files for each type > instead having it mixed all together. > > * All these polygons have overlapping ways. This should be avoided > because it creates tones of duplicate nodes/ways. Each polygon should > be split in single ways and the area defined with a relation. > According to the description, mapshaper will do that to. There may be > a way to do this with postgis or through a Perl script.
You can use ogr2osm to convert from shapefile to .osm deduplicating common nodes and ways and creating multipolygons as appropriate. http://svn.openstreetmap.org/applications/utils/import/ogr2osm/ Cheers _______________________________________________ Imports mailing list Imports@openstreetmap.org http://lists.openstreetmap.org/listinfo/imports