Overlays

[pdavidc]

Provide a mechanism for hierarchically grouping features. From the COE requirements document:

Overlays (feature grouping)

• The map engine shall support a concept of hierarchical overlays which are containers for groups of features, and child overlays.
• Overlays shall be able to have visibility toggled on and off showing / hiding all child overlays and features
• Overlays shall be able to be removed resulting I all child overlays and features also being removed
• Overlays shall have a z-index making it possible to control which overlays feature data appears on top or below another overlays feature data
• Map engine shall provide a way to retrieve an overlay by unique id

[pdavidc]

NASA comments on the COE requirements document:

WorldWind provides this capability through the layer mechanism. It’s possible for applications to implement the grouping feature mentioned here using layers. Z-control is provided based on layer order.