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4.0.1 Using the Field Selector
The Field Selector is used to select data sources, parameters, data times, and types of displays to use for creating visualizations.
Field Selector

The Field Selector consists of 4 panels:

images/FieldSelectorWindow.gif
Data Sources
When the IDV reads in a data source, most of the time it only reads enough metadata to be able to create a list of data choices. Some of the datasets may be quite large and this allows you to only read those portions that you need instead of the entire dataset.
  1. Right click the sample_eta_grid.nc data source in the Data Sources panel of the Field Selector window and select the Properties menu.
  2. Each Data Source Properties Dialog will have one or more tabs for setting and viewing the properties of that data source. Tab through the properties of this data source.
  3. Click the Cancel button to close the window
Data Choices (Fields)
When a data source is loaded, a set of data choices are created from the metadata. This allows you to select a subset of the dataset.
  1. Select the sample_eta_grid.nc data source in the Data Sources panel of the Field Selector window.
  2. In the Fields panel, you will see two tabs - 3D grid and 2D grid indicating that this dataset has both 2D and 3D fields in it.
  3. Click on the little tab to the left of the 3D grid field to expand that tab. The list contains those 3D fields from the dataset that the IDV can display.
  4. Select the temperature field. When you select a field, the Displays and Data Subset panels are populated with entries applicable to that field.

Derived Choices

When a data source creates the list of data choices from the parameters in a dataset, it also uses a library of pre-defined derived quantities to create a list of choices for fields that can be calculated from the fields in the dataset.

Displays
When each data choice is created, the metadata for that choice is used to determine which displays are applicable to that field.
  1. Look at the list of available display types for your Dewpoint selection in the Displays panel.
  2. Select the Flow Vectors (from GridRelative_u & GridRelative_v) field and notice that the list of displays changes.
  3. Select the Sounding Data (T & dewpoint only) field and notice that you get another list of displays.
  4. Select Dewpoint (from T & RH) again.
  5. In the Displays panel, select Contour Plan View] so we can create a horizontal slice of the data and display it as contours.
Data Subsetting
The Data Subset panel allows you to temporally and spatially subset the data you've chosen. For this exercise, we will look at subsetting by time and level.

Times

Each data choice may or may not have times associated with it which are displayed in the Times panel. If there is a set of times, you can select all or just a subset of times to be displayed. There are two ways you can select a subset of times.

Levels

Each data choice may or may not have levels associated with it which are displayed in the Level tab of the Data Subset panel. If you do not select a level, the entire volume is read in.

When you are finished making all your selections, click the Create Display button to apply them and create the display. The subset of data you selected will be read from the data source and displayed in the currently active View Window.
images/MainWindowTD.gif

 


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U09-NRM-127: The role of Distributed Data Access Technologies in NRM - for ITC-IDV version 2.7 > Accessing and Displaying Data > Data Selection Overview