# Overlay Layers (GeoAnalytics Desktop)

## Summary

Overlays the geometries from multiple layers into a single layer. Overlay can be used to combine, erase, modify, or update spatial features.

Overlay is used to answer one of the most basic questions of geography, What is on top of what? The following are examples:

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

## Usage

• Use 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 intersect certain watersheds. Overlay Layers can be used to find intersecting areas.
• A development company wants to build a 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 supported overlay methods and input geometries are described in the following table:

Input and Overlay geometry typesIntersectEraseUnionIdentitySymmetric Difference

Point and point

Point and polyline

Point and polygon

Polyline and point

Polyline and polyline

Polyline and polygon

Polygon and point

Polygon and polyline

Polygon and polygon

Overlay methodDescription

Intersect

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.

This is the default.

Erase

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

Union

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

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

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

• This geoprocessing tool is powered by Spark. Analysis is completed on your desktop machine using multiple cores in parallel. See Considerations for GeoAnalytics Desktop tools to learn more about running analysis.

• When running GeoAnalytics Desktop tools, the analysis is completed on your desktop machine. For optimal performance, data should be available on your desktop. If you are using a hosted feature layer, it is recommended that you use ArcGIS GeoAnalytics Server. If your data isn't local, it will take longer to run a tool. To use your ArcGIS GeoAnalytics Server to perform analysis, see GeoAnalytics Tools.

## Syntax

`OverlayLayers(input_layer, overlay_layer, out_feature_class, overlay_type)`
 Parameter Explanation Data Type input_layer The point, line, or polygon features that will be overlaid with the overlay layer. Feature Layer overlay_layer The features that will be overlaid with the input layer features. Feature Layer out_feature_class A new feature class with overlaid features. Feature Class overlay_type Specifies 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.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

## Code sample

OverlayLayers example (stand-alone script)

The following Python window script demonstrates how to use the OverlayLayers tool.

``````#-------------------------------------------------------------------------------
# Name: OverlayLayers.py
# Description: Remove areas that are already developed from proposed development sites

# Import system modules
import arcpy

arcpy.env.workspace = "c:/data/data.gdb"
# Set local variables
inFeatures = "areasOfInterest"
overlayFeatures = "commercial"
out = "DevelopmentSites"
overlayType = "ERASE"

# Execute Overlay Layers
arcpy.gapro.OverlayLayers(inFeatures, overlayFeatures, out,
overlayType)``````

## Licensing information

• Basic: No
• Standard: No
• Advanced: Yes