On Fri, Sep 19, 2014 at 3:17 PM, Ben Koziol - NOAA Affiliate < [email protected]> wrote:
> Storing geometries inside netCDF is something I've also been thinking > about. I even went as far as to start writing some code to do this for > polygons (https://github.com/bekozi/ncvec) using ragged arrays. > This seems like the "right" way to do it to me -- if you have a bunch of related things that aren't the same size, what you really want it in a ragged array. Not CF I know... > CF kinda-sorts support ragged arrays: http://cfconventions.org/Data/cf-conventions/cf-conventions-1.6/build/cf-conventions.html#Example%20H.2.4.1 At least you could do polygons in a similar fashion, and maybe propose an addition to CF. > I also have some Python code for converting polygons from a watersheds > shapefile into the UGRID format ( > https://github.com/ugrid-conventions/ugrid-conventions/blob/v0.9.0/ugrid-conventions.md#2d-flexible-mesh-mixed-triangles-quadrilaterals-etc-topology). > The major limitation here is that UGRID expects no gaps between the "faces" > which limits its ability to store multi-geometries (i.e. Hawaii). > It also expects each "face" to have the same number of vertices, more or less. But it's a good idea to leverage that -- let's keep things as consistent as possible. And you may be abel to do it pretty much in UGRID, but storing: nodes: these would be all the vertices of all the polygons boundary_node_connectivity: this would specify the segments that define the polygons then use a polygon_index variable, or something, that would be n_boundaries in length, and specify which segments belonged to which polygon. Though, unless your goal is interoperability with UGRID for one reason or another, probably better to use a ragged-array approach. -Chris -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception [email protected]
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