Saving and Loading Overlay Groups

In CDAT, the Overlay Groups area in the Layers | Overlay control tab lets you save and load a set of overlays that you frequently use. Overlay groups are useful for when you’ve created a complex set of overlays, arranged them in the correct order, changed their properties, and want to save and re-use them.

As an example of loading an overlay group, open any of the example data files that you're familiar with (the examples below show chlorophyll concentration from the example_viirs_chlor_sep_2022.nc data file), then:

  1. Select the Layers | Overlay control tab.
  2. In the Overlay Groups list select the Oceanographic group.
  3. Click the Load button at the bottom of the list (or you can also double-click Oceanographic).
  4. A set of overlays is added to the Overlay List.

Your data view will have overlays that look like the following:

CDAT window showing chlorophyll data in the eastern Atlantic with the oceanographic overlay group.

To create and save your own custom overlay group:

  1.  Optional: Start fresh by removing any existing overlays using the  Remove button.
  2. Create, edit, and rearrange your own set of overlays. 
  3. Click the Create button in the Overlay List — a Create new overlay group window will appear.
  4. Select the overlays for your new group (Ctrl-click or ⌘-click to select multiple items).
  5. Enter your new group name in the text field or select an existing overlay group in the list to replace it.
  6. Click Save. 

The following is an example of a custom set of overlays being saved:

CDAT window showing custom overlay group save window for ocean color data

Now you can load your custom group by selecting it in the Overlay Groups list and clicking the  Load button.  The new overlays are inserted into the Overlay List before any existing items — it often makes sense to clear out any overlays before opening a new group.

NOTE: You cannot save a shape overlay to a group because it references an external data file.

Bonus exercises:

  • Read the user's guide Section 3.5.3 on overlay groups.
  • Click the Help or ? button at the bottom of the overlay layers tab and read the CDAT in-application help on overlays and overlay groups.
  • Try opening the Atmospheric overlay group.
  • Read the user's guide Section 3.11 on user preferences to see where overlay groups are stored (or select Open User Resources Directory from the Tools | Preferences menu).  Try installing the NOAAOceanColorMasks.jso file from the cw_utils_sample_data.zip Download cw_utils_sample_data.zip file into your <RESOURCES>/overlays/  directory for use with the Multilayer Mask Overlays exercises.