[Imports] California land cover import

[andrzej zaborowski]

Hi,

2009/12/31  <srmixter at 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