Overlay Layers

Overlay Layers icon The Overlay Layers tool combines two layers into a single layer using various methods including intersect, erase, union, identity, and symmetrical difference.

Workflow diagram

Overlay layers workflow diagram

Example

  • The department of environmental quality wants to monitor the impact of livestock grazing on the state's water quality. Biologists with the department need to determine where the land deemed to be grazing allotments intersects with certain watersheds. Overlay layers via an intersect operation can be used to find intersecting areas.
  • A development company wants to build a new golf resort in one of three centrally located counties in their state. Before they can begin planning, they need to determine whether there is enough privately owned land within those counties available to purchase for the resort. Overlay layers via an erase operation can be used to remove the publicly owned lands from the selected counties.

Usage notes

  • Sliver features may be excluded based on the tolerance of the processing spatial reference.
  • The following table outlines the available overlay operations per input and overlay geometry types:

    Input and overlay geometry typesIntersectEraseUnionIdentitySymmetric difference

    Point and point

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    Point and polyline

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    Point and polygon

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    Polyline and point

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    Polyline and polyline

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    Polyline and polygon

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    Polygon and point

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    Polygon and polyline

    Polygon and polygon

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  • The supported overlay methods and input geometries are described in the following table:

    Overlay methodDescription

    Intersect

    overlay intersect icon

    The features or portions of features in the overlay that overlap the input features are preserved. The input and feature geometry must be the same.

    Erase

    overlay erase icon

    The features or portions of features in the overlay features that overlap the input features are removed.

    Union

    overlay union icon

    The result will contain a geometric union of the input layer and overlay layer. All features and their attributes will be written to the layer.

    Identity

    overlay identity icon

    The result will contain features or portions of features of the input features and overlay features. Features or portions of features that overlap in both input layer and overlay layer will be written to the output layer.

    Symmetric difference

    overlay symmetric difference icon

    The result will contain features or portions of features of the input layer and the overlay layer that do not overlap.

Parameters

ParameterDescriptionData Type

Input Layer

The input layer for the overlay operation.

Features

Overlay Layer

The overlay layer for the overlay operation.

Features

Overlay Operation

Specifies the type of overlay to be performed. Overlay operations include:

  • Intersect - Computes a geometric intersection of the input layers. Features or portions of features that overlap in both the input layer and overlay layer will be written to the output layer.
  • Erase - Only those features or portions of features in the overlay layer that are not within the features in the input layer are written to the output.
  • Union - Computes a geometric union of the input layer and overlay layer. All features and their attributes will be written to the layer.
  • Identity - Computes a geometric intersection of the input features and identity features. Features or portions of features that overlap in both input layer and overlay layer will be written to the output layer.
  • Symmetrical Difference - Features or portions of features in the input layer and overlay layer that do not overlap will be written to the output layer.

String

Output layer

The output layer will retain the same schema of the input layer.

Considerations and limitations

  • Input and overlay layers may be point, line, or polygon features.