Union (Coverage)

Summary

Computes the geometric intersection of two polygon coverages. All polygons from both coverages will be split at their intersections and preserved in the output coverage.

Learn more about how Union works

Illustration

Union Illustration

Usage

Syntax

Union_arc (in_cover, union_cover, out_cover, {fuzzy_tolerance}, {join_attributes})
ParameterExplanationData Type
in_cover

The coverage whose polygons will be combined with the union coverage.

Coverage
union_cover

The union coverage whose polygons will be combined with the input coverage.

Coverage
out_cover

The output coverage that will be created containing the results of the operation.

Coverage
fuzzy_tolerance
(Optional)

The minimum distance between coordinates in the output coverage. By default, the minimum fuzzy tolerance value from the input and union coverages is used.

Learn more about how the default fuzzy tolerance is calculated

Double
join_attributes
(Optional)

Specifies whether all items in both the input and the union coverage will be joined to the output coverage feature attribute table.

  • JOINAll items from both coverages will appear in the output coverage feature attribute table. If duplicate item names are encountered, the item in the input coverage will be maintained, and the one in the join file will be dropped. This is the default option and is used unless NO_JOIN is specified.
  • NO_JOINOnly the feature's internal number (cover#) from the input coverage and the union coverage are joined in the output coverage feature attribute table. This option is useful in reducing the size of the output coverage feature attribute table. The cover# field can then be used in the Add Join tool to link the features in the resulting coverage back to the features in the input or union coverage.
Boolean

Code Sample

Union example (stand-alone script)

The following stand-alone script demonstrates how to union two coverages.

# Name: Union_Example.py
# Description: Unions two coverages
# Requirements: ArcInfo Workstation
# Author: ESRI

# Import system modules
import arcpy
from arcpy import env

# Set environment settings
env.workspace = "C:/data"

# Set local variables
inCover = "tong_azone"
unionCover = "tong_flood2"
outCover = "C:/output/studyarea"
joinAttributes = "NO_JOIN"

# Execute Union
arcpy.Union_arc(inCover, unionCover, outCover, "", joinAttributes)

Environments

Related Topics

Licensing Information

ArcView: No
ArcEditor: No
ArcInfo: Requires ArcInfo Workstation installed

Published 6/8/2010