On Fri, Sep 19, 2014 at 3:17 PM, Ben Koziol - NOAA Affiliate <
ben.koziol at noaa.gov> 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
Chris.Barker at noaa.gov
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Received on Mon Sep 22 2014 - 10:40:15 BST
