# Cell Types For Unstructured Grid CF standard

Similar to the data types that already exist NetCDF Users Guide, we could add cell types to the netCDF library which describe the geometry of a cell. This would provide the information about how many vertices a cell has and there for how many node index values to expect in the connectivity. Each cell type would have a standard node ordering which describes how to format and use the connectivity data.

0 NC_PTS A series of scattered points: earthquake locations 1 NC_TRK A series of connected points: Drifter data 2 NC_LIN An arbitrary list of lines each described by two end points: edge data 3 NC_TRI Triangles described by the location of three vertices's 4 NC_QAD Quadrilaterals described by the location of four vertices's 5 NC_PNT etc 6 NC_HEX etc 7 NC_SPT etc 8 NC_OCT etc 9 NC_MXD Mixed 2D polygon cells 43 NC_TETRAHEDRON ! Numbers are based on: #of faces #of sides 64 NC_HEXAHEDRON 1443 NC_PYRAMID ! for more complex types: #of faces #of sides #of faces #of sides 3423 NC_WEDGE 9999 NC_UNSTRUCT ! MIXED 3D solids cells

*Better formatting?*

**we need good pictures to do this properly'''
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## questions

- Not sure about these 3D types:
- other suggestions for numbering, naming, geometries?

- Do extruded cells need an NC_XXXXX integer typing?
- For each of these we need to define a node numbering scheme,

a face numbering scheme, and an edge numbering scheme

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