Plots from Gridded Data

2.3 Plots from Gridded Data

This section describes how to make plots from gridded data sets. The set of steps involve:

2.3.0	Connecting to a Data Source on a Remote Server
2.3.1	Selecting the display to be made
2.3.2	To make a plot of 3D data
2.3.3	Subsetting Times
2.3.4	Spatial Subsetting

2.3.0 Connecting to a Data Source on a Remote Server

In the Data Chooser select the Catalogs tab.

../data/choosers/images/CatalogChooser.gif

Choose one of the remote Catalogs: such as https://resources.unidata.ucar.edu/georesources/idvcatalog.xml for Unidata's catalog of near real-time model output.

A tree view of the catalog will be displayed. Open one, such as the "NCEP NAM 80km CONUS model data (real and near time)", by clicking on one of the tab icons ( icon ).

The list of this model's run times appears. Click on one time to select it, and then click on the Add Source button. You have selected this model run's output to be accessible by the IDV.

2.3.1 Selecting the display to be made

The gridded data source that you selected will be shown in the Field Selector window. In the Fields panel are folders of data categorized as 2D and 3D fields. Click on the 2D grid tab ( icon

) to expand that category list. A list of all 2D grid parameters in the data source appears. When one of the fields is selected the list of applicable displays will be shown. For a complete list of example displays, see Example Displays.

Try creating a Contour Plan View by selecting that display in the list and clicking on the Create Display button. The display will be created and shown in the main window. The display's legend should also be shown. You can bring up the control window by right clicking on the name in the legend and selecting Control Window from the popup menu.

2.3.2 To make a plot of 3D data

Click on the 3D grid tab to expand that category. A list of all 3D grid parameters appears. To make a plot, first click on a parameter name such as "Geopotential height at isobaric levels."

Display types suitable for this parameter are listed in then Displays panel. Select Contour Plan View and click on the Create Display button.

The initial plot is at the lowest level in the data grid, such as 1000 millibar in this example. To shift the level to other levels:

Right click on the legend (such as "T Contour Plan View Level 1000") to get a pop-up menu.
Click on Control Window to bring up this display's Control window
In the Control window click on the Levels: box to bring up the pop-up menu of native grid levels in the data
select the desired level, such as 500, from the list.

The plot will move to 500 millibars.

To zoom, rotate or pan this 3D display, see Zoom, Rotate, and Pan. Rotate the display by dragging with the right mouse button. (you see that the 500 millibar contours are above the surface). The key combination Ctrl-R will restore the display to the original overhead view.

To toggle on the time animation loop, use the Run/Stop icon in the animation control. Read more about Time Animation Widget.

To remove an existing display, use the File->Remove Display menu of the display's control window or the popup menu.

2.3.3 Subsetting Times

The IDV automatically loads data for all data times selected in the data selection step, and loads them as displays for an animation loop. Creating several displays may take time. If you only need to see one data time, it is better to only create displays for that time.

To make time selections that apply to all data in one data source, double click on the data source name in the left panel of the Field Selector window to bring up the Data Source Properties editor. Click on the Times tab to subset the times.

Initially all times are selected for display by the IDV - indicated by the times in this window being grayed out and the box "Use All" being checked. To limit the selection to fewer times than all times, first check off the box "Use All." Then select the times you want to use by clicking on the times (note: you can select multiple times with the Shift and Control keys).

To make time selections for one field, use the Times selector in the lower right panel of the Field Selector, under the Displays panel, after you select the field, and before you create the display. This will override the default times for the data source.

2.3.4 Spatial Subsetting

You can also spatially subset the grid using the Spatial Subset tab of the Data Source Properties or the Field Selector. This works similar to the times subsetting where you can set the property for all fields in the Data Source or override the default for a particular field.

For more information on time and spatial subsetting, see the Data Source Properties page of this User's Guide.

Unidata's Integrated Data Viewer > Getting Started