Using IDV Via OPeNDAP

There are several OPeNDAP external tools that can access and display HDF-EOS data directly. Here we use IDV to display HDF-EOS5 data. Follow these simple steps to display the data of interest.

We use a NASA OMI HDF-EOS5 data for illustration. You can also download it here external . More OMI data served with OPeNDAP can be found at NASA GES DISC .

1. Download and install IDV

For more information about how to download and install IDV, click here external

2. Start IDV

When IDV starts for the first time, you will see three windows respectively:

2.a IDV Help Tips window. An optional window with tips on using the IDV. You can close this window.

Figure 1 Help Window
2.b Dashboard window. Used for selecting data to analyze and visualize.

Figure 2 Dashboard
2.c Unidata IDV window. This is the main window for displaying data visualizations.

Figure 3 Main Window

3. Choose the HDF file

You need to choose the data you want to display. Currently you have three options to choose the data:

Option 1: Clicking the Data Choosers tab on the dashboard window. Toward the left side of the window there is a list of options to choose the data. Click URLs under General
Option 2: Clicking Data on the main menu and then choosing Choose Data
Option 3: Clicking File on the main menu and then choosing New->Data Source

and provide (copy & paste) the following example OPeNDAP URL:

        http://acdisc.sci.gsfc.nasa.gov/opendap/HDF-EOS5/Aura_OMI_Level3/OMTO3d.003/2009/OMI-Aura_L3-OMTO3d_2009m0531_v003-2012m0406t062756.he5
      

Figure 4 Type an example OPeNDAP URL

in the URL: box and choose Data from an OPeNDAP server in the Data Source Type box. Alternatively, if the above NASA URL doesn't work, you can try The HDF Group OPeNDAP demo server URL that serves the same data:

        https://eosdap.hdfgroup.org:8080/opendap/data/NASAFILES/hdf5/OMI-Aura_L3-OMTO3d_2009m0531_v003-2009m0602t070659.he5
      

Figure 5 Type an alternate OPeNDAP URL

You would see a window like:

Figure 6 Data Chooser

4. Display the HDF data

Once the data is loaded you will be taken to the Field Selector window. The Field Selector window is divided into four sub-categories: Data Sources, Fields, Displays and Region Stride. This window is used to select the field to be displayed and the visualization option.

Figure 7 Field Selector

In order to create a display:

Select the data of interest from the Data Source window
Select the data field you want to display. To do this, you need to click the 'Fields' name(2D grid in this example) under Fields, Then choose the data field you want to display(Best Total Ozone Solution in this example).
Select the display type. In this case click Plan Views and then select Color-Shaded Plan View.
Optionally use the subsetting list to have the required (region, time, stride etc.) settings.
Press Create Display

You can view the data in the Unidata workshop IDV window. It should look like:

Figure 8 Map View

Last modified: 11/11/2020