EFDC+ allows the export of NetCDF-CF (NetCDF- Climate and Forecast) formatted data. This allows EFDC+ output to be read and displayed on web servers. According to the UNIDATA User GuideAccording to the Unidata website the Network Common Data Form (NetCDF) software was originally intended to create, access, and share array-oriented data in a form that is self-describing and portable. These deal with a variety of data types that encompass single-point observations, time series, regularly-spaced grids, and satellite or radar images.
The NetCDF The NetCDF software functions as an input/output (I/O) library , that can be accessed from many scientific data processing and GIS software packages and different programming languages, such as C, FORTRAN, Fortran 90, C++, Java, Perl, Python, MATLAB, and other languages for which a NetCDF library is available. The A NetCDF library stores and retrieves data in self-describing, machine-independent datasets. Each NetCDF dataset , which are described on the Unidata website. The NetCDF user guide provides details on how NetCDF datasets can contain multidimensional, named variables (with different of various types that include integers, reals, characters, bytes, etc.), and each variable may be accompanied by ancillary data, such as units of measure or descriptive text. The interface includes a method for appending data to existing NetCDF datasets in prescribed ways, functionality that is not unlike a (fixed length) record structure. However, the NetCDF library also allows direct-access storage and retrieval of data by variable name and index and therefore is useful only for disk-resident (or memory-resident) datasets. You can learn about NetCDF compression here.
NetCDF is designed to:
• Facilitate the use of common datasets by distinct applications.
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• Establish an interface standard that simplifies the design of new software for accessing geoscience data.
There is now an unstructured (or flexible mesh) model data format for NetCDF called UGRID. From the EEMS10.4 version, DSI enhanced the NetCDF capabilities of the EFDC_Explorer Modeling System (EEMS), so that it is able to handle the UGRID format. Although UGRID is designed for unstructured grids, the advantage for EFDC+ and structured grids is that it writes output for only the active grid cells, rather than the full I,J grid required by web map services for displaying environmental data such as ncWMS. Furthermore, the structure of the output variables is clearly defined, along with the variable name and units. This allows users to easily process EFDC+ output using third-party software. UGRID is also based on the CF Metadata Conventions, but this approach currently assumes that the horizontal topology should be determined from the cell index of the EFDC+ grid rather than the I,J indices of the structured grid. The new version of EFDC+ is able to export UGRID approach adds conventions to specify the topology for unstructured (e.g., triangular) grids.
UGRID also provides powerful new capabilities for display on third-party web tools, some of which are listed here. This will provide an enhanced user experience when accessing real-time models using a WebGIS application.
EFDC+ can currently write the native output in NetCDF-CF format for Windows and Linux. EEEFDC_Explorer , (the pre-and post-processor for for EFDC+) can also convert EFDC the binary files output by EFDC+ (*.OUT files ) to netCDF.nc files, including the derived WQ water quality parameters. EFDC+ currently currently exports 44 parameters to NetCDF format. This allows EFDC+ output to be read and displayed on web servers.
EFDC+ exports the NetCDF files at the same interval that it produces the model linkages files, which is set in the tab for Timing and Linkage | Linkage | NetCDF.
The main configuration for NetCDF output is in the EFDC_Exlporer Linkage | NetCDF tabs as shown in Figure 1. Here the user can turn on netCDF output by checking the Output to NetCDF checkbox. The user may select the level at which the NetCDF data is compressed with the Deflate Level setting. This can range from 1, no compression, to 9 for maximum compression, but is recommended by UNIDATA Unidata to be set to 2 for the best balance between file size and speed.
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To convert the .nc file to s text file, the user can download the ncdump.exe tool and follow step-by-step instruction in UNIDATAUnidata.
1.1.2. Using ArcMap
A detailed guidance video for visualizing NetCDF output using ArcMap has been prepared by DSI and made available here: https://www.youtube.com/watch?v=vgT7dN4UK44
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ncWMS loads native netCDF files and displays them on a web browser. To make the output the same as EE8 EE10 would require further adjustment to the tool. For the purposes of this demonstration, the basic display of the output is shown in the next section.
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