After selecting a top-level item type in the filters menu, markers for every second level item type appear on the map by default. The user can then filter further by checking off second level item types, but there should be an indicator that 'all' are included first.
For example:
Item Type:
Event
Event Types
All Event Types
D.C. History
Marches and Rallies
Openings and Dedications
Encampment
Environmental Disaster
Concerts
Concert
Cultural Gathering
Inaugurations
Remembrances
Planning and Design
Here, "All Event Types" would be checked by default. If the user selected any of the other Event Types, "All Event Types" would lose its checked state.
After selecting a top-level item type in the filters menu, markers for every second level item type appear on the map by default. The user can then filter further by checking off second level item types, but there should be an indicator that 'all' are included first.
For example:
Item Type: Event
Event Types
Here, "All Event Types" would be checked by default. If the user selected any of the other Event Types, "All Event Types" would lose its checked state.