NetCDF Unstrukturiertes Gitter

Kurze Beschreibung

Ein aus beliebigen Polygonen - Dreiecke und Vierecke - aufgebautes Gitter wird beschrieben. Typische Dateitypen hierfür sind z. B. untrim_grid.dat sowie utrsub_grid.dat. Die Speicherung von Daten auf diesem Gitter, z. B. der Tiefe (Bathymetrie), wird an anderer Stelle beschrieben (siehe NetCDF Synoptische Daten im Dreiecksgitter). Ebenso werden hier keine Informationen über offene und geschlossene Kanten oder Positionen zum Einsteuern von Randwerten aufgeführt. Es wird ausschließlich die Struktur (Topologie) des Gitters beschrieben.

Die Beschreibung wurde vollständig für die staggered data Positionen node, edge und poly gestaltet.

Inhalt der Datei

Dimensionen

• Siehe NetCDF Dreiecksgitter, Abschnitt "Dimensionen".
• Zusätzlich zu den dort angegebenen Dimensionen werden noch benötigt:

  dimensions:

  nMaxMesh2_poly_nodes = maximum number of nodes in polygon ;

Lokale Koordinaten

Knoten

double Mesh2_node_x(nMesh2_node) ;

Mesh2_node_x:standard_name = "projection_x_coordinate" ;

Mesh2_node_x:long_name = "x-coordinate of 2D mesh nodes" ;

Mesh2_node_x:units = "m" ;

double Mesh2_node_y(nMesh2_node) ;

Mesh2_node_y:standard_name = "projection_y_coordinate" ;

Mesh2_node_y:long_name = "y-coordinate of 2D mesh nodes" ;

Mesh2_node_y:units = "m" ;

Kanten

double Mesh2_edge_x(nMesh2_edge) ;

Mesh2_edge_x:standard_name = "projection_x_coordinate" ;

Mesh2_edge_x:long_name = "x-coordinate of 2D mesh edges, e.g. center of edge" ;

Mesh2_edge_x:units = "m" ;

Mesh2_edge_x:bounds = "Mesh2_edge_x_bnd" \\ optional

double Mesh2_edge_y(nMesh2_edge) ;

Mesh2_edge_y:standard_name = "projection_y_coordinate" ;

Mesh2_edge_y:long_name = "y-coordinate of 2D mesh polygons, e.g. center of edge" ;

Mesh2_edge_y:units = "m" ;

Mesh2_edge_y:bounds = "Mesh2_edge_y_bnd" \\ optional

Polygone

double Mesh2_poly_x(nMesh2_poly) ;

Mesh2_poly_x:standard_name = "projection_x_coordinate" ;

Mesh2_poly_x:long_name = "x-coordinate of 2D mesh polygons, e.g. center of gravity or circumcenter" ;

Mesh2_poly_x:units = "m" ;

Mesh2_poly_x:bounds = "Mesh2_poly_x_bnd" \\ optional

double Mesh2_poly_y(nMesh2_poly) ;

Mesh2_poly_y:standard_name = "projection_y_coordinate" ;

Mesh2_poly_y:long_name = "y-coordinate of 2D mesh polygons, e.g. center of gravity or circumcenter" ;

Mesh2_poly_y:units = "m" ;

Mesh2_poly_y:bounds = "Mesh2_poly_y_bnd" \\ optional

(optional) Begrenzung für Kanten

double Mesh2_edge_x_bnd(nMesh2_edge,Two) ; \\ no metadata required

double Mesh2_edge_y_bnd(nMesh2_edge,Two) ; \\ no metadata required

(optional) Begrenzung für Polygone

double Mesh2_poly_x_bnd(nMesh2_poly,Three) ; \\ no metadata required

double Mesh2_poly_y_bnd(nMesh2_poly,Three) ; \\ no metadata required

Geografische Koordinaten

Knoten

double Mesh2_node_lon(nMesh2_node) ;

Mesh2_node_lon:standard_name = "longitude" ;

Mesh2_node_lon:long_name = "longitude of 2D mesh nodes" ;

Mesh2_node_lon:units = "degrees_east" ;

double Mesh2_node_lat(nMesh2_node) ;

Mesh2_node_lat:standard_name = "latitude" ;

Mesh2_node_lat:long_name = "latitude of 2D mesh nodes" ;

Mesh2_node_lat:units = "degrees_north" ;

Kanten

double Mesh2_edge_lon(nMesh2_edge) ;

Mesh2_edge_lon:standard_name = "longitude" ;

Mesh2_edge_lon:long_name = "longitude of 2D mesh edges, e.g. center of edge" ;

Mesh2_edge_lon:units = "degrees_east" ;

Mesh2_edge_lon:bounds = "Mesh2_edge_lon_bnd" // optional

double Mesh2_edge_lat(nMesh2_edge) ;

Mesh2_edge_lat:standard_name = "latitude" ;

Mesh2_edge_lat:long_name = "latitude of 2D mesh edges, e.g. center of edge" ;

Mesh2_edge_lat:units = "degrees_north" ;

Mesh2_edge_lat:bounds = "Mesh2_edge_lat_bnd" // optional

Polygone

double Mesh2_poly_lon(nMesh2_poly) ;

Mesh2_poly_lon:standard_name = "longitude" ;

Mesh2_poly_lon:long_name = "longitude of 2D mesh polygons, e.g. center of gravity or circumcenter" ;

Mesh2_poly_lon:units = "degrees_east" ;

Mesh2_poly_lon:bounds = "Mesh2_poly_lon_bnd" // optional

double Mesh2_poly_lat(nMesh2_node) ;

Mesh2_poly_lat:standard_name = "latitude" ;

Mesh2_poly_lat:long_name = "latitude of 2D mesh polygons, e.g. center of gravity or circumcenter" ;

Mesh2_poly_lat:units = "degrees_north" ;

Mesh2_poly_lat:bounds = "Mesh2_poly_lat_bnd" // optional

(optional) Begrenzung für Kanten

double Mesh2_edge_lon_bnd(nMesh2_edge,Two) ; \\ no metadata required

double Mesh2_edge_lat_bnd(nMesh2_edge,Two) ; \\ no metadata required

(optional) Begrenzung für Polygone

double Mesh2_poly_lon_bnd(nMesh2_poly,Three) ; \\ no metadata required

double Mesh2_poly_lat_bnd(nMesh2_poly,Three) ; \\ no metadata required

Topologische Daten

Knotenverzeichnis der Kanten

integer Mesh2_edge_nodes(nMesh2_edge,Two) ;

Mesh2_edge_nodes:standard_name = "???" \\ yet to be determined

Mesh2_edge_nodes:long_name = "list of nodes for all edges, start node - end node"

Bemerkung: Indizes starten mit Null!

Knotenverzeichnis der Polygone

integer Mesh2_poly_nodes(nMesh2_poly,Three) ;

Mesh2_poly_nodes:standard_name = "???" \\ yet to be determined

Mesh2_poly_nodes:long_name = "list of nodes for all polygons, counterclockwise"

Bemerkung: Indizes starten mit Null!

Polygonverzeichnis der Kanten

integer Mesh2_edge_polys(nMesh2_edge,Two) ;

Mesh2_edge_polys:standard_name "???" \\ yet to be determined

Mesh2_edge_polys:long_name = "list of (adjacent) polygons for all edges - left and right neigbour polygon"

Mesh2_edge_polys:_FillValue = fillvalue \\ indicates missing neighbour polygon, e.g. at domain boundaries

Bemerkung: Indizes starten mit Null!

Topologievariable

integer Mesh2 ;

Mesh2:standard_name = "???" \\ yet to be determined ;

Mesh2:long_name = "can be used to store a name for the grid" ;

Mesh2:dimensionality = 2 ; \\ flat mesh, no three-dimensional elements;

Mesh2:locations = "node edge poly" \\ data can be assigned to these locations ;

Mesh2:node_coordinates = "Mesh2_node_lon Mesh2_node_lat" ;

Mesh2:edge_coordinates = "Mesh2_edge_lon Mesh2_edge_lat" ;

Mesh2:poly_coordinates = "Mesh2_poly_lon Mesh2_poly_lat" ;

Mesh2:poly_node_connectivity = "Mesh2_poly_nodes" ;

Mesh2:edge_node_connectivity = "Mesh2_edge_nodes" ;

Mesh2:edge_poly_connectivity = "Mesh2_edge_polys" ; \\ different from Deltares

Koordinatentransformation

integer crs ; \\ value is equivalent to the EPSG code of the transformation

crs:grid_mapping_name = "transverse_mercator" ;

crs:scale_factor_at_central_merdian = value ;

crs:longitude_of_central_meridian = value ;

crs:latitude_of_projection_origin = value ;

crs:false_easting = value ;

crs:false_northing = value ;

Anmerkungen, Fragen

• Datei nutzt Deltares-CF-Erweiterungen. Ausnahme ist das Attribut edge_poly_cennectivity in der Topologievariable.
• Können auch für Kanten bounds angegeben werden?
• Müssen die Begrenzungen für beide Koordinatensysteme angegeben werden?
• Müssen die Indizes unbedingt mit Null starten?
• Die Beschreibung der Koordinatentransformation ist für UTM- und Gauß-Krüger-Koordinaten geeignet.

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