Geodatabase Schema Overview#

The contents of an NG911 geodatabase must conform to the specifications set out in the Standard.

Feature Datasets#

The geodatabase should contain at its top level two feature datasets: the required feature dataset NG911 and the optional feature dataset OptionalLayers. Both feature datasets should use a coordinate reference system prescribed by the Standard.

Feature Classes#

A compliant geodatabase must contain eight feature classes in the NG911 feature dataset. These include the point feature class ADDRESS_POINT, the line feature class ROAD_CENTERLINE, and the polygon feature classes DISCREPANCYAGENCY_BOUNDARY, ESB_EMS_BOUNDARY, ESB_FIRE_BOUNDARY, ESB_LAW_BOUNDARY, ESZ_BOUNDARY, and PSAP_BOUNDARY.

The Toolkit does not currently have any functionality related to optional feature classes.

Fields and Domains#

All required feature classes must have the fields specified by the Standard. They must not contain any additional fields (other than those required automatically created for geodatabase feature classes, such as OBJECTID), and the fields must be configured correctly (e.g., the data types must be correct). Further, some fields are required to have domains assigned to them, and those domains must be defined as specified by the Standard.

Topology Rules#

The Standard prescribes a number of topological relationships that must hold true within and between required feature classes.

One-Member Rules#

Rule	Member
Must Not Overlap (Area)	`DISCREPANCYAGENCY_BOUNDARY`
Must Not Have Gaps (Area)	`ESB_EMS_BOUNDARY`
Must Not Have Gaps (Area)	`ESB_FIRE_BOUNDARY`
Must Not Have Gaps (Area)	`ESB_LAW_BOUNDARY`
Must Not Have Gaps (Area)	`PSAP_BOUNDARY`
Must Not Overlap (Line)	`ROAD_CENTERLINE`
Must Not Have Dangles (Line)	`ROAD_CENTERLINE`
Must Not Self-Overlap (Line)	`ROAD_CENTERLINE`
Must Not Self-Intersect (Line)	`ROAD_CENTERLINE`
Must Be Single Part (Line)	`ROAD_CENTERLINE`

Two-Member Rules#

Member 1	Rule	Member 2
`ADDRESS_POINT`	Must Be Properly Inside (Point-Area)	`DISCREPANCYAGENCY_BOUNDARY`
`ROAD_CENTERLINE`	Must Be Inside (Line-Area)	`DISCREPANCYAGENCY_BOUNDARY`
`ESB_EMS_BOUNDARY`	Must Cover Each Other (Area-Area)	`DISCREPANCYAGENCY_BOUNDARY`
`ESB_FIRE_BOUNDARY`	Must Cover Each Other (Area-Area)	`DISCREPANCYAGENCY_BOUNDARY`
`ESB_LAW_BOUNDARY`	Must Cover Each Other (Area-Area)	`DISCREPANCYAGENCY_BOUNDARY`
`ESZ_BOUNDARY`	Must Cover Each Other (Area-Area)	`DISCREPANCYAGENCY_BOUNDARY`
`PSAP_BOUNDARY`	Must Cover Each Other (Area-Area)	`DISCREPANCYAGENCY_BOUNDARY`

Exceptions#

The ADDRESS_POINT and ROAD_CENTERLINE feature classes include the field TopoExcept, which allows users to flag individual features as exempt from certain rules.

`DANGLE_EXCEPTION`#

In ROAD_CENTERLINE only, setting TopoExcept = DANGLE_EXCEPTION exempts a feature from the rule Must Not Have Dangles (Line).

`INSIDE_EXCEPTION`#

In ADDRESS_POINT, setting TopoExcept = INSIDE_EXCEPTION exempts a feature from the rule Must Be Properly Inside (Point-Area) with respect to DISCREPANCYAGENCY_BOUNDARY.

In ROAD_CENTERLINE, setting TopoExcept = INSIDE_EXCEPTION exempts a feature from the rule Must Be Inside (Line-Area) with respect to DISCREPANCYAGENCY_BOUNDARY.

`BOTH_EXCEPTION`#

In ROAD_CENTERLINE only, setting TopoExcept = BOTH_EXCEPTION applies the effects of both DANGLE_EXCEPTION and INSIDE_EXCEPTION