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Zonal Geometry

Available with Spatial Analyst license.

Summary

Calculates the specified geometry measure (area, perimeter, thickness, or the characteristics of ellipse) for each zone in a dataset.

Learn more about how Zonal Geometry works

Illustration

Zonal Geometry illustration
OutRas = ZonalGeometry(InRas1,"VALUE","AREA")

Usage

  • A zone is defined as all areas in the input that have the same value. The areas do not have to be contiguous. Both raster and feature can be used for the zone input.

  • If the Input raster or feature zone data (in_zone_data in Python) has overlapping polygons, the zonal analysis will not be performed for each individual polygon. Since the feature input is converted to a raster, each location can only have one value.

    An alternative method is to process the zonal operation iteratively for each of the polygon zones and collate the results.

  • When specifying the Input raster or feature zone data (in_zone_data in Python), the default zone field will be the first available integer or text field. If no other valid fields exist, the ObjectID field (for example, OID or FID) will be the default.

  • The data type of the output raster for each of the geometry types will be floating point.

  • If a particular zone consists of only one cell or if the zone is a single square block of cells, the orientation of the ellipse (which, in this case, is a circle) is set to 90 degrees.

  • See Analysis environments and Spatial Analyst for additional details on the geoprocessing environments that apply to this tool.

Syntax

ZonalGeometry (in_zone_data, zone_field, {geometry_type}, {cell_size})
ParameterExplanationData Type
in_zone_data

Dataset that defines the zones.

The zones can be defined by an integer raster or a feature layer.

Raster Layer; Feature Layer
zone_field

Field that holds the values that define each zone.

It must be an integer field of the zone dataset.

Field
geometry_type
(Optional)

Geometry type to be calculated.

  • AREA The area for each zone.
  • PERIMETER The perimeter for each zone.
  • THICKNESS The deepest (or thickest) point within the zone from its surrounding cells.
  • CENTROID Locates the centroids of each zone.
String
cell_size
(Optional)

The processing cell size for the zonal operation.

This is the value in the environment if specifically set. If the environment is not set, the default for the cell size is determined by the type of the zone data as follows:

  • If the zone dataset is a raster, the cell size is the same as the zone raster.
  • If the zone dataset is a feature, the cell size is the shorter of the width or height of the extent of the zone feature dataset in the output spatial reference, divided by 250.

Analysis Cell Size

Return Value

NameExplanationData Type
out_raster

The output zonal geometry raster.

Raster

Code sample

ZonalGeometry example 1 (Python window)

This example determines the area for each zone defined by the input polygon shape file.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outZonalGeometry = ZonalGeometry("zones.shp", "Classes", "AREA", 0.2)
outZonalGeometry.save("C:/sapyexamples/output/zonegeomout3")
ZonalGeometry example 2 (stand-alone script)

This example determines the area for each zone defined by the input polygon shape file.

# Name: ZonalGeometry_Ex_02.py
# Description:Calculates for each zone in a dataset the specified geometry 
#   measure (area, perimeter, thickness, or the characteristics 
#   of ellipse).
# Requirements: Spatial Analyst Extension

# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *

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

# Set local variables
inZoneData = "zones.shp"
zoneField = "Classes"
cellSize = 0.2

# Execute ZonalStatistics
outZonalGeometry = ZonalGeometry(inZoneData, zoneField, "AREA", cellSize)  

# Save the output 
outZonalGeometry.save("C:/sapyexamples/output/zonegeomout2")

Licensing information

  • ArcGIS Desktop Basic: Requires Spatial Analyst
  • ArcGIS Desktop Standard: Requires Spatial Analyst
  • ArcGIS Desktop Advanced: Requires Spatial Analyst

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