Using McIDAS-V via OPeNDAP

There are several OPeNDAP tools that can access and display NASA HDF/HDF-EOS data directly. Here we use McIDAS-V to display HDF-EOS5 data. Follow these simple steps to display a dataset from remote HDF/HDF-EOS file via OPeNDAP.

We use a NASA AURA OMI HDF-EOS5 data for illustration.

1. Download and install McIDAS-V

You can download the latest McIDAS-V from here . Please click here for installation instruction.

2. Start McIDAS-V

When McIDAS-V starts for the first time, you will see three windows respectively:

1. McIDAS-V Help Tips window. An optional window with tips on using the McIDAS-V. You can close this window.
   
   Figure 1. Help Tips Window
   
2. Data Explorer window. Used for selecting data to analyze and visualize.
   
   Figure 2. Data Explorer
   
3. McIDAS-V window. This is the main window for visualizing data with map.
   
   Figure 3. McIDAS-V Window
   

3. Choose the HDF file

You need to choose the data you want to display. Please follow the steps to choose the data:

1. Click the Data Sources tab on the Data Explorer window. Toward the left side of the window there is a list of options to choose the data. Expand General TreeView item and click the URLs node.
2. Choose Grid files (netCDF/GRIB/OPeNDAP/EMPAK) in the Data Type: drop-down selection box.
3. Type the example OPeNDAP URL:
   Figure 4. Type an example OPeNDAP URL

   https://eosdap.hdfgroup.org:8080/opendap/data/NASAFILES/hdf5/OMI-Aura_L3-OMDOAO3e_2004m1001_v003-2008m0222t095640.he5
   in the URL: drop-dwon text selection box.
4. Press the Add Sourcebutton on the right bottom corner.

You will see a window like Figure 5:

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 panes: Data Sources, Fields, Displays, and Region/Stride. This window is used to select the field to be displayed and the visualization option.

To create a display:

1. Select the data of interest from the Data Sources: pane.
2. Select a grid type that you want to display by expanding a TreeView item (2D grid in this example) under Fields TreeView pane. Then, choose the data field that you want to display (Ozone vertical column density in this example).
3. Select the display type. For example, click Plan Views TreeView item and then choose Color-Shaded Plan View.
4. Optionally, subset data by unchecking Use Default check box first and selecting a region with mouse.
5. Press the Create Display button.

The selected data field will appear in the McIDAS-V window. It will look like Figure 7.

Last modified: 11/11/2020