Page History

example_unstructured_grid_config.zip

DELFT-FEWS is a location oriented system. All time series data must be referenced to a (geographic) location. Scalar time series need no additional information. For grid time series data, each point in the grid must be referenced to a location in a grid structure.

...

In irregular grids the grid has a fixed number of rows and columns, but the cell height and width is not equal in each row and column. For these grids additional information is required on the location of each individual cell in the grid to allow display in the grids display as well as for use in the spatial interpolation routine.

For regular grids it is sometimes not required to add the location to the grids.xml when you only want to import/export the grid. Most grid transformations will not work when the output location is missing in the grids.xml. Regular grids that need a custom projection (projectionFile, polarStereoGraphic, geostationarySatelliteView, transverseMercator, mercator, albersEqualArea, azimuthalEquidistant, lambertAzimuthalEqualArea, rotatedCartesian, lambertConformalConic, rotatedSouthPole, rotatedNorthPole, rotatedCartesian, azimuthalEquidistant) should ALWAYS be listed in the grids.xml. The grid geometry should be available in the imported file (netcdf/grib).

When available on the file system, the name of the XML file is for example:

...

Figure 28 Elements of the grids configuration

regular

Definition of a regular grid. One or more regular grids may be defined.

...

Optional, when specified the grid cell boundaries can be based on the neighbour neighbor cells. Number of rows and columns in grid, at least two rows and two columns. Don't configure this for scattered point grids.

...

Coordinate system the grid is defined in. This may be a different coordinate system to that used in the main map display. The coordinate system may also differ per grid. A grid may be regular in one coordinate system, but may be irregular in another. Defining the grid in the regular coordinate system is generally easier.

You can also use the EPGS codes

cellCentre

Definition of the cell centre points of all cells in the irregular grid. The number of cellCentre points defined must be the same as the number of cells in the grid (rows x columns).

...

Since 2013.01. Csv file with cell centers. Csv file should contain an "x" and "y" column. The cell centers should be listed from the upper left to the lower right, row by row. For regular grids always try to use a regular grid with a (custom) geodatum. For config example see: 06Grids-ConfigExamples

netcdfFile

Since 2015.02. Reference to a UGRID NetCDF file that contains only grid geometry meta data. This only supports mesh topologies (unstructured grids) with 2D coordinates. This can be 1D network, 2D triangular, 2D flexible or 3D layered mesh topologies. This currently only works for files that are compliant to the UGRID 1.0 conventions. For more information see httpshttp://ugrid-conventions.github.comio/ugrid-conventions/ugrid-conventions

Irregular grid definition from a UGRID NetCDF file

file

Name of a UGRID NetCDF file in the map layer files folder or a full absolute path to a UGRID NetCDF file. The file must have extension ".nc".

...

Name of a mesh topology variable in the UGRID NetCDF file that contains the meta-data attributes of the mesh on which the data is defined.

...

The (stagger) location within the mesh at which the data is defined. Only node, edge and face are supported. Data defined at nodes or edges will be handled as points in FEWS. Data defined at faces will be handled as polygons in FEWS. If the mesh in the netcdf file does not contain valid face bound coordinate variables, then data defined at faces will be handled as points in FEWS.

locationIndexSetVariableName

Name of a location index set variable in the NetCDF file that contains the indices of the locations at which the data is defined. The location index set variable in the NetCDF file should point to a mesh topology variable and a (stagger) location within the mesh. This is only supported if the location index set variable in the NetCDF file contains coordinates (i.e. a coordinates attribute that points to coordinate variables that contain only coordinates for the index set, not for the entire mesh).

Using a UGRID NetCDF file as unstructured grid definition

To import/export unstructured grid/flexible mesh data in Delft-FEWS, use a timeSeriesImport/ExportRun with type "NETCDF-CF_GRID" or use a generalAdapter import/exportNetcdfActivity. For this to work you need to add an irregular grid definition to the grids.xml configuration file. The easiest way to do this, is by using the option "netcdfFile" (see above) that refers to a NetCDF file that contains a UGRID mesh topology (and no data).

In an unstructured grid the data can be defined either on the nodes, the edges or the faces of the mesh (staggerLocations). Also see http://ugrid-conventions.github.io/ugrid-conventions/#data-defined-on-unstructured-meshes.

An example configuration can be downloaded here: example_unstructured_grid_config.zip. The example shows what is minimally needed to be present in the UGRID NetCDF file and how one can configure it in FEWS.

Each grid definition in grids.xml is valid for only one staggerLocation and this should match the staggerLocation of the data that you are going to import using the grid definition. The staggerLocation on which the data is defined can be deduced from the data variable in a netcdf file that contains the data to import. The data variable (e.g. "water_level") has an attribute called "location" and a dimension (e.g. nmesh2d_face) that both indicate its staggerLocation. In the grid geometry choose the corresponding staggerLocation. If you want to import different data variables that are defined on different staggerLocations in the same mesh, then you will have to create separate grid definitions for different staggerLocations using the same mesh from the same netcdf file, e.g.:

<irregular locationId="SFBayFM_data_on_faces">
    <netcdfFile>
        <file>sfbay_flowgeom.nc</file>
        <geoDatum>UTM10N</geoDatum>
        <meshTopologyVariableName>mesh2d</meshTopologyVariableName>
        <staggerLocation>face</staggerLocation>
    </netcdfFile>
</irregular>
<irregular locationId="SFBayFM_data_on_nodes">
    <netcdfFile>
        <file>sfbay_flowgeom.nc</file>
        <geoDatum>UTM10N</geoDatum>
        <meshTopologyVariableName>mesh2d</meshTopologyVariableName>
        <staggerLocation>node</staggerLocation>
    </netcdfFile>
</irregular>

D-Flow FM (Dutch: D-HYDRO)

It is possible to use a D-Flow flexible mesh (D-Flow FM) flowgeom UGRID NetCDF file, produced by a D-Flow FM model run, as grid definition in Delft-FEWS. If your D-Flow FM model run does not produce a flowgeom file, then add the following line in the D-Flow FM .mdu file in the output section, e.g.:

[output]
...
FlowGeomFile    = f34_flowgeom.nc    # *_flowgeom.nc Flow geometry file in NetCDF format.
...

The produced flowgeom file must be in UGRID 1.0 NetCDF format. Therefore you must use MapFormat = 4 in the D-Flow FM .mdu file in the output section:

[output]
...
MapFormat    = 4    # Map file format, 1: netCDF, 2: Tecplot, 3: netCFD and Tecplot, 4: NetCDF-UGRID
...

The flowgeom file format will match the configured map file format. If MapFormat is set to 4, then D-Flow FM will produce a valid UGRID file. With MapFormat set to 1 it will produce a format that looks very much like UGRID, but is not the same. Delft-FEWS can only use valid UGRID files. Using MapFormat 1 files with Delft-FEWS may cause problems.

If you have set MapFormat = 4, but the flowgeom file produced by D-Flow FM still causes errors in Delft-FEWS, then you may need to update to a newer version of DFlow-FM (1.2.2 or later). Note that in that case, you can manually create a valid flowgeom from the map file by removing all variables that depend on time from the netcdf file. This can be done using the third party command line tool nccopy, using a command like this (with uppercase -V):

nccopy -V mesh2d,wgs84,mesh2d_node_x,mesh2d_node_y,mesh2d_node_z,mesh2d_edge_nodes,mesh2d_edge_x,mesh2d_edge_y,mesh2d_edge_x_bnd,mesh2d_edge_y_bnd,mesh2d_face_nodes,mesh2d_face_x,mesh2d_face_y,mesh2d_face_x_bnd,mesh2d_face_y_bnd,mesh2d_FlowElem_ba,mesh2d_FlowElem_bl,mesh2d_edge_type map.nc flowgeom.nc

The tool nccopy is part of the NetCDF library binary distribution.

Config Examples

<irregular locationId="meshLocation">
	<netcdfFile>
		<file>simplebox_hex7_map.nc</file>
		<meshTopologyVariableName>mesh2d<<meshTopologyVariableName>insert_mesh_variable_name_here</meshTopologyVariableName>
		<staggerLocation>face</staggerLocation>
	</netcdfFile>
</irregular>

...

<irregular locationId="Swan2D_G2_cellcenters">
	<rows>1318</rows>
	<columns>317</columns>
	<esriShapeFile>
		<file>swan2D_G2_cellcenters.shp</file>
		<projectionFileAvailable>true</projectionFileAvailable>
		<x>%X%</x>
		<y>%Y%</y>
	</esriShapeFile>
</irregular>

<irregular locationId="Grid_Waqua_Zeedelta">
    <rows>1539</rows>
    <columns>501</columns>
    <csvFile>
        <file>Grid_Waqua_Zeedelta.csv</file>
        <geoDatum>Rijks Driehoekstelsel</geoDatum>
        <x>%X%</x>
        <y>%Y%</y>
    </csvFile>
</irregular> 

<regular locationId="KNMI-HIRLAM-V70">
	<description>grid def. for KNMI-HIRLAM v7.0 with rotated pole</description>
	<rows>226</rows>
	<columns>136</columns>
	<rotatedSouthPole>
		<latitude>-30</latitude>
		<longitude>-15</longitude>
	</rotatedSouthPole>
	<gridCorners>
		<geoDatum>WGS 1984</geoDatum>
		<upperLeft>
			<x>-30.8688</x>
			<y>79.63847</y>
		</upperLeft>
		<lowerRight>
			<x>10.29617</x>
			<y>26.065</y>
		</lowerRight>
	</gridCorners>
</regular>

...

<regular locationId="QPF">
	<description>QPF Grid for ABRFC</description>
	<rows>159</rows>
	<columns>335</columns>
	<polarStereographic>
		<originLatitude>90.0</originLatitude>
		<originLongitude>-105.0</originLongitude>
		<scaleAtOrigin>0.933</scaleAtOrigin>
		<equatorRadius>6367470.0</equatorRadius>
		<poleRadius>6367470.0</poleRadius>
	</polarStereographic>
	<gridCorners>
		<geoDatum>WGS 1984</geoDatum>
		<upperLeft>
			<x>-106.67471389477944</x>
			<y>39.37455858318055</y>
			<z>0.0</z>
		</upperLeft>
		<lowerRight>
			<x>-92.34455929643786</x>
			<y>32.390342856654044</y>
			<z>0.0</z>
		</lowerRight>
	</gridCorners>
</regular>

Generating XML

...

For NetCDF and GRIB files you can generate the grids.xml with F12>Clipboard>Copy grib geometry form file