Layers used in VO can be grouped to four (4) different types:

  1. Hydrologic Object Layers – Layers that are used to store and display hydrologic objects.
  2. Support Layers – Layers that provide support functions.
  3. Base Map Layers – Layers that provide background map data (Available only in ArcGIS).
  4. Imported Layers – Layers added by users.

Both the Hydrologic Object Layers and Support Layers are system layers and are saved in the project file. They can’t be removed from Table of Content.