Polygon - Single Layer Overlap

Overlaps occur when there are areas that are covered by more than one polygon feature. The Polygon - Single Layer Overlap quality control (QC Quality Control) check identifies areas where geometry overlaps exist within a polygon layer.

Note: By default, this QC check accounts for snapping tolerance. Polygon features with over 1 million vertices will be simplified to ensure performance. Projection-Based Unit is used in this check. Projection-Based Unit indicates the unit of measurement is pulled from the Spatial QC Projection this data target uses. If no Spatial QC Projection is used in this data target, the unit is pulled from the Data Target's projection.

Note: By default, Polygon - Single Layer Overlap accounts for snapping tolerance within GIS Geographic Information System. A computer application that involves storing and manipulating electronic maps and related data. Also, mapping software combining spatial information about where places and events are located with data attributes describing those places and events. editing applications. The following are applied automatically when the Sliver Filter parameter is configured.
- Feet: When configured to 0, the check runs with built-in tolerance of 0.0087 feet for all spatial reference systems measured in feet like most state plane projections.
- Meters: When configured to 0, the check runs with built-in tolerance of 0.0027 meters for all spatial reference systems measured in meters.

To run this check, a polygon feature class is required.

Configurations for QC check parameters contain filters to prevent selecting incompatible field types.

The following parameters can be specifically configured for the Polygon - Single Layer Overlap QC check.

  • Run On: Non-configurable. This QC check inspects the target dataset.

  • Severity: Sets the importance level of this QC check’s fallouts. Critical fallouts prevent export package outputs but will still provide fallouts.

  • Polygon Layer Name: The polygon layer that will be analyzed for overlaps. For example: Law_Boundary or EMS Emergency Medical Service. Response centers for services such as ambulance, fire department, hospital, and poisen control center._Boundary.

  • Reporting Unique ID: A unique identifier in the polygon layer that can be used to uniquely identify a singular feature.

  • Smallest Overlap to Report (Projection-Based Unit): Use to ignore overlaps smaller than a specified square area. 0 enforces the highest level of accuracy.

  • Sliver Filter (Projection-Based Unit): Shrinks overlap dimensions from all sides by this set distance to remove slivers from the results. 0 is strongly recommended and enforces the highest level of accuracy. For example, a 0.5 ft filter would shrink a 50 ft × 1 ft overlap to 49 ft × 0 ft, excluding it from the fallouts.

The following information is included for this QC check's fallout output.

  • QC check name
  • Description of the QC check
  • Feature class where the fallout appears
  • Extended information providing more details about the fallout
  • Latitude and Longitude of the fallout's location

The example below shows a possible error message you may receive when a record fails the Polygon - Single Layer Overlap QC check. The extended information provides the layer name, the polygons that overlap, and the size of the overlap detected in either square meters or feet.

Here is an example of possible error messages that may be received for the QC check.

In the example below, the boundaries between ESN Emergency Service Number. A three to five digit number representing a unique combination of emergency service agencies (law enforcement, fire and emergency medical service) designated to serve a specific range of addresses within a particular geographical area, or Emergency Service Zone (ESZ). The ESN facilitates selective routing and selective transfer, if required, to the appropriate PSAP and dispatching of the proper service agency(ies). 001 and ESN 002 do not aligned perfectly. A polygon overlap is detected here.

Here is an image of two boundary layers with an overlap demonstrating the results of the Polygon Overlaps QC check.