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‎cf/cellconnectivity.py‎

Lines changed: 54 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -6,31 +6,57 @@
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class CellConnectivity(mixin.PropertiesData, cfdm.CellConnectivity):
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"""A cell connectivity construct of the CF data model.
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TODOUGRID
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A cell measure construct provides information that is needed about
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the size or shape of the cells and that depends on a subset of the
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domain axis constructs. Cell measure constructs have to be used
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when the size or shape of the cells cannot be deduced from the
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dimension or auxiliary coordinate constructs without special
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knowledge that a generic application cannot be expected to have.
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The connectivity measure construct consists of a numeric array of the
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metric data which spans a subset of the domain axis constructs,
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and properties to describe the data. The connectivity measure construct
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specifies a "measure" to indicate which metric of the space it
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supplies, e.g. connectivity horizontal areas, and must have a units
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property consistent with the measure, e.g. square metres. It is
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assumed that the metric does not depend on axes of the domain
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which are not spanned by the array, along which the values are
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implicitly propagated. CF-netCDF connectivity measure variables correspond
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to connectivity measure constructs.
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A cell connectivity construct defines explicitly how cells
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arranged in two or three dimensions in real space but indexed by a
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single domain (discrete) axis are connected. Connectivity can only
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be provided when the domain axis construct also has a domain
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topology construct, and two cells can only be connected if they
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also have a topological relationship. For instance, the
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connectivity of two-dimensional face cells could be characterised
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by whether or not they have shared edges, where the edges are
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defined by connected nodes of the domain topology construct.
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The cell connectivity construct consists of an array recording the
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connectivity, and properties to describe the data. There must be a
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property indicating the condition by which the connectivity is
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derived from the domain topology. The array spans the domain axis
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construct with the addition of a ragged dimension that indexes a
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unique identity for the cell as well as the identities of all
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other cells to which it is connected. The cell identity must be
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recorded in the first element of the ragged dimension, otherwise
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the order is arbitrary. Note that the connectivity array for point
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cells is, by definition, equivalent to the array of the domain
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topology construct.
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When cell connectivity constructs are present they are considered
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to be definitive and must be used in preference to the
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connectivities implied by inspection of any other constructs,
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apart from the domain topology construct, which are not guaranteed
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to be the same.
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In CF-netCDF a cell topology construct can only be provided by a
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UGRID mesh topology variable. The construct array is supplied
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either indirectly by any of the UGRID variables that are used to
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define a domain topology construct, or directly by the UGRID
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"edge_edge_connectivity" variable (for edge cells) or
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"face_face_connectivity" variable (for face cells). In the direct
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case, the integer indices contained in the UGRID variable may be
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used as the cell identities, although the CF data model attaches
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no significance to the values other than the fact that some values
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are the same as others.
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Restricting the types of connectivity to those implied by the
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geospatial topology of the cells precludes connectivity derived
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from any other sources, but is consistent with UGRID encoding
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within CF-netCDF.
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See CF Appendix I "The CF Data Model".
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**NetCDF interface**
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{{netCDF variable}}
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.. versionadded:: TODOUGRIDVER
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.. versionadded:: UGRIDVER
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"""
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@@ -44,9 +70,14 @@ def __repr__(self):
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@property
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def connectivity(self):
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"""TODOUGRID Measure which indicates the metric of space supplied.
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"""The connectivity type.
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.. versionadded:: TODOUGRIDVER
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{{cell connectivity type}}
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.. versionadded:: UGRIDVER
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.. seealso:: `del_connectivity`, `get_connectivity`,
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`has_connectivity`, `set_connectivity`
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"""
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return self.get_connectivity(default=AttributeError())
@@ -78,7 +109,7 @@ def identity(
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* The netCDF variable name, preceded by ``'ncvar%'``.
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* The value of the *default* parameter.
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.. versionadded:: TODOUGRIDVER
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.. versionadded:: UGRIDVER
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.. seealso:: `id`, `identities`, `long_name`, `connectivity`,
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`nc_get_variable`, `standard_name`

‎cf/domaintopology.py‎

Lines changed: 82 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -6,31 +6,84 @@
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class DomainTopology(mixin.PropertiesData, cfdm.DomainTopology):
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"""A domain topology construct of the CF data model.
88
9-
TODOUGRID
10-
11-
A cell measure construct provides information that is needed about
12-
the size or shape of the cells and that depends on a subset of the
13-
domain axis constructs. Cell measure constructs have to be used
14-
when the size or shape of the cells cannot be deduced from the
15-
dimension or auxiliary coordinate constructs without special
16-
knowledge that a generic application cannot be expected to have.
17-
18-
The cell measure construct consists of a numeric array of the
19-
metric data which spans a subset of the domain axis constructs,
20-
and properties to describe the data. The cell measure construct
21-
specifies a "measure" to indicate which metric of the space it
22-
supplies, e.g. cell horizontal areas, and must have a units
23-
property consistent with the measure, e.g. square metres. It is
24-
assumed that the metric does not depend on axes of the domain
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which are not spanned by the array, along which the values are
26-
implicitly propagated. CF-netCDF cell measure variables correspond
27-
to cell measure constructs.
9+
A domain topology construct defines the geospatial topology of
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cells arranged in two or three dimensions in real space but
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indexed by a single (discrete) domain axis construct, and at most
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one domain topology construct may be associated with any such
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domain axis. The topology describes topological relationships
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between the cells - spatial relationships which do not depend on
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the cell locations - and is represented by an undirected graph,
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i.e. a mesh in which pairs of nodes are connected by links. Each
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node has a unique arbitrary identity that is independent of its
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spatial location, and different nodes may be spatially co-located.
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The topology may only describe cells that have a common spatial
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dimensionality, one of:
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* Point: A point is zero-dimensional and has no boundary vertices.
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* Edge: An edge is one-dimensional and corresponds to a line
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connecting two boundary vertices.
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* Face: A face is two-dimensional and corresponds to a surface
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enclosed by a set of edges.
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Each type of cell implies a restricted topology for which only
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some kinds of mesh are allowed. For point cells, every node
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corresponds to exactly one cell; and two cells have a topological
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relationship if and only if their nodes are connected by a mesh
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link. For edge and face cells, every node corresponds to a
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boundary vertex of a cell; the same node can represent vertices in
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multiple cells; every link in the mesh connects two cell boundary
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vertices; and two cells have a topological relationship if and
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only if they share at least one node.
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A domain topology construct contains an array defining the mesh,
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and properties to describe it. There must be a property indicating
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the spatial dimensionality of the cells. The array values comprise
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the node identities, and all array elements that refer to the same
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node must contain the same value, which must differ from any other
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value in the array. The array spans the domain axis construct and
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also has a ragged dimension, whose function depends on the spatial
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dimensionality of the cells.
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For point cells, the array's ragged dimension values are composed
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of the node identity of each cell in the first element, followed
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in arbitrary order by the identity of each node to which it is
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connected by a mesh link.
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For edge and face cells, the array's ragged dimension values are
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the node identities of the boundary vertices of each cell, in the
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same order that the boundary vertices are stored by the auxiliary
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coordinate constructs. Each boundary vertex except the last is
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connected by a mesh link to the next vertex along the ragged
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dimension, and the last vertex is connected to the first.
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When a domain topology construct is present it is considered to be
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definitive and must be used in preference to the topology implied
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by inspection of any other constructs, which is not guaranteed to
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be the same.
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In CF-netCDF a domain topology construct can only be provided for
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a UGRID mesh topology variable. The information in the construct
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array is supplied by the UGRID "edge_nodes_connectivity" variable
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(for edge cells) or "face_nodes_connectivity" variable (for face
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cells). The topology for node cells may be provided by any of
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these three UGRID variables. The integer indices contained in the
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UGRID variable may be used as the mesh node identities, although
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the CF data model attaches no significance to the values other
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than the fact that some values are the same as others. The spatial
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dimensionality property is provided by the "location" attribute of
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a variable that references the UGRID mesh topology variable,
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i.e. a data variable or a UGRID location index set variable.
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See CF Appendix I "The CF Data Model".
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**NetCDF interface**
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{{netCDF variable}}
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The netCDF variable name of the UGRID mesh topology variable may
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be accessed with the `nc_set_variable`, `nc_get_variable`,
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`nc_del_variable`, and `nc_has_variable` methods.
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.. versionadded:: TODOUGRIDVER
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.. versionadded:: UGRIDVER
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"""
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@property
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def cell(self):
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"""TODOUGRID Measure which indicates the metric of space supplied.
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"""The cell type.
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.. versionadded:: TODOUGRIDVER
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{{cell type}}
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.. versionadded:: UGRIDVER
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.. seealso:: `del_cell`, `get_cell`, `has_cell`, `set_cell`
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"""
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return self.get_cell(default=AttributeError())
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@cell.setter
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def cell(self, value):
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def cell(self, value):
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self.set_cell(value)
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@cell.deleter
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* The netCDF variable name, preceded by ``'ncvar%'``.
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* The value of the *default* parameter.
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.. versionadded:: TODOUGRIDVER
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.. versionadded:: UGRIDVER
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.. seealso:: `id`, `identities`, `long_name`, `cell`,
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`nc_get_variable`, `standard_name`

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