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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
Current content can be found at unidata.ucar.edu.
To learn about what's going on, see About the Archive Site.
Hi Nathan,With the holidays etc. I haven't had a chance yet to respond to this until now.
Yes, sort of. Actually the GridDataSource class is an abstract class that simply holds the 2d and 3d data categories. For netcdf files a GeoGridDataSource is created which knows how to handle gridded netcdf files (a sub-class knows howI'm trying to modify IDV to retrieve a catalog of gridded data and then the gridded data itself from a specific web service. This catalog and retrieval would look quite similar to the current IDV Catalog chooser.My question is: Is there a way to create a GridDataSource without a .nc file? It appears that once a user chooses a model and time and clicks Add Source, IDV creates a DataSource of type GridDataSource and retrieves a .nc file from the ucar server. This Data Source is then used to display all the available 2D and 3D parameters and forecast times in the Data Selector window, and the same data source is also used when creating the display. Is that correct?
to handle OpenDap based data)
The issue is that from the web service I will only be receiving XML. The XML document would describe the grid data, including parameters and forecast times. But the actual .nc file will not be available until the final step of Create Display, and it seems that IDV needs the .nc file for a grid data source at the step of Add Source in the Chooser window. I have no intention of heavily modifying the baseline of IDV, I'm only adding functionality on top of it. I'm just interested in knowing if there's something I'm missing or not understanding about DataSources for gridded data and how they are used to fill the Data Selector window and then create a display.
So you'll have an xml document that defines a collection of available data sources - e.g., like our catalog chooser. Does the granularity of this xml doc go down to the parameter level? or is that held in another document. For example, our catalog chooser lists the model data available. The user selects a particular model/run and then the GeoGridDataSource is created that then opens the netcdf file (or queries the opendap server) to determine
the parameters/times.If you end up having an xml document that describes the fields available you could create a DataSource class that reads the xml, creates the appropriate DataChoices and knows how to read the data for a particular
field and create the appropriate visad.Data data structure.
On an unrelated note, nice easter eggs. ;)
Shhh.
There is another unidata group that is developing Java libraries for reading in a variety of data formats, including Grib.And just out of curiousity, does anyone know of any active work on enabling IDV to read GriB files directly?
We are hoping to integrate this effort into the IDV in the coming months. -Jeff
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