Overlay Layers (Standard Feature Analysis)

Summary

Overlays the geometries from multiple layers into one single layer. Overlay can be used to combine, erase, modify, or update spatial features. Overlay is much more than a merging of geometries; all the attributes of the features taking part in the overlay are carried through to the result.

Overlay is used to answer one of the most basic questions of geography, "What is on top of what?"

• What parcels are within the 100-year floodplain? (Within is just another way of saying on top of.)
• What roads are within what countries?
• What land use is on top of what soil type?
• What wells are within abandoned military bases?

Illustration

Usage

• Examples include the following:

  • The department of environmental quality wants to monitor the impact of grazing livestock 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 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 that they may be able to purchase for the resort. Overlay Layers can be used to remove the publically owned lands from the selected counties.

• The Overlay Layers tool requires two inputs: an input layer and an overlay layer. The availability of overlay method options depends on whether the input and overlay layers are points, lines, or areas.

  Overlay Method	Input Layer	Overlay Layer	Description
  Intersect	Points, lines, or areas	Points, lines, or areas	The features or portions of features in the input that are overlapped with the overlay features are kept. The type of output can be specified as Points, Lines, or Areas when intersecting line or area features. The dimension of the output geometry type must be the same or less than both the input and overlay dimensions, where Points=0 dimensions, Lines=1 dimension, and Areas=2 dimensions. This is the default method.
  Union	Areas	Areas	The input and overlay areas are combined.
  Erase	Areas	Points, lines, or areas	The features or portions of features in the input areas that are overlapped with the overlay features are removed.

Syntax

arcpy.sfa.OverlayLayers(inputLayer, overlayLayer, outputName, {overlayType}, {outputType}, {snapToInput}, {tolerance})

Parameter	Explanation	Data Type
inputLayer	The point, line, or polygon features that will be overlaid with the overlay layer.	Feature Set
overlayLayer	The features that will be overlaid with the input layer features.	Feature Set
outputName	The name of the output layer to create on your portal.	String
overlayType (Optional)	The type of overlay to be performed. 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. This is the default. UNION —Computes a geometric union of the input layers. All features and their attributes will be written to the output layer. This option is only valid if both the input layer and the overlay layer contain polygon features. 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.	String
outputType (Optional)	The type of intersection you want to find. This parameter is only valid when the overlay type is Intersect. INPUT —The features returned will be the same geometry type as the input layer or overlay layer with the lowest dimension geometry. If all inputs are polygons, the output will contain polygons. If one or more of the inputs are lines and none of the inputs are points, the output will be line. If one or more of the inputs are points, the output will contain points. This is the default. LINE — Line intersections will be returned. This is only valid if none of the inputs are points. POINT — Point intersections will be returned. If the inputs are line or polygon, the output will be a multipoint layer.	String
snapToInput (Optional)	Specifies if feature vertices in the input layer are allowed to move. The default is NO_SNAP and means if the distance between features is less than the tolerance value, all features from both layers can move to allow snapping to each other. When the value is SNAP, only features in the overlay layer can move to snap to the input layer features. NO_SNAP —Allow features from both layers to snap their vertices to each other. This is the default. SNAP —Only allow features in the overlay layer to move vertices to snap to the input layer.	Boolean
tolerance (Optional)	A double value of the minimum distance separating all feature coordinates as well as the distance a coordinate can move in X or Y (or both). The units of tolerance are the same as the units of the input layer's coordinate system.	Double

Derived Output

Name	Explanation	Data Type
output	The features that are the result of the overlay. The type of feature (point, line, or polygon) depends on the input parameter settings.	Feature Set

Environments

Extent

Licensing information

• Basic: Requires your account in ArcGIS Enterprise to have the Perform Analysis privilege
• Standard: Requires your account in ArcGIS Enterprise to have the Perform Analysis privilege
• Advanced: Requires your account in ArcGIS Enterprise to have the Perform Analysis privilege