Tabulate Intersection

• A zone is comprised of all features in the Input Zone Features that have the same values in the Zone Field(s). Similarly, a class is comprised of all features in the Input Class Features that have the same values in the Class Field(s). Features do not have to be contiguous to be in the same zone or class. This tool calculates how much of the zone is intersected by each class (area and percentage of zone area).

• If no Class Field(s) is specified, all features in the Input Class Features will be considered a single class. The Output Table will contain one record for each zone.

• If Class Field(s) is specified, the Output Table will contain n records for each zone, where n is the number of classes within that zone. For example, if a zone contains four classes, the Output Table will have four records for that zone.

• Numeric attributes from the Input Class Features can be summed by zone using the Sum Fields parameter. The sum values for a class represent a proportion of the sum values based on the percentage of the class intersecting the zone (similar to how a Ratio Policy works).

  Only fields with absolute values (not relative, normalized values such as percentages or densities) should be used as Sum Fields, since the values may be split and apportioned to different zones.

• Using higher dimension Input Class Features than the Input Zone Features is not supported. Unsupported combinations:

  • Zone = Points, Class = Polygons or Lines
  • Zone = Lines, Class = Polygons

• When the Input Zone Features and Input Class Features are polygons, the output table statistics will be based on area calculations.

  When the Input Class Features are lines, the output table statistics will be based on linear calculations.

  When the Input Class Features are points, the output table statistics will be based on feature count.

• When the Input Zone Features and the Input Class Features are the same dimension (both polygon, both line, or both point), the output PERCENTAGE field records the percentage of the zone feature that is intersected by the class.

  If the Input Zone Features and the Input Class Features are different dimensions (polygon zone with line class, polygon zone with point class, or line zone with point class), the output PERCENTAGE field records the percentage of the class intersecting the zone polygon.

  It is possible for the PERCENTAGE field to record a percent value greater than 100 percent when there are overlapping features in the Input Zone Features or the Input Class Features.

• The AREA field is included in the output table only when the Input Zone Features and Input Class Features are polygon. The AREA field contains the area of the Input Zone Features that the Input Class Features intersect.

  A LENGTH field is included in the output table when the Input Class Features are lines. The LENGTH field contains the length of intersection between the Input Zone Features and the Input Class Features.

  A PNT_COUNT field is included in the output table when the Input Class Features are points. The PNT_COUNT field contains the count of the number of Input Class Features points that intersect the Input Zone Features.

• When using feature layers, if any features are selected, only the selected features are used in calculations.

• Determining the intersection of zone and class features is done following the same rules as the Intersect tool.

• Use the Pivot Table tool to transform the Output Table into a table that contains one record for each zone with class attributes as separate attribute fields. Fill in the parameters for the Pivot Table tool as follows:

  • Input Table—Tabulate Intersection Output Table
  • Input Field(s)—Tabulate Intersection Zone Field(s)
  • Pivot Field—Tabulate Intersection Class Field
  • Value Field—Tabulate Intersection Sum Field or AREA, LENGTH, PERCENTAGE

Using TabulateIntersection in the Python window to find the area of each vegetation type in each zone.

import arcpy
arcpy.TabulateIntersection_analysis("Zones", "zone_id", "Vegetation", r"C:\Esri\veganalysis.gdb\vegtypeAreas", "VEGTYPE")
                    

Script that wraps TabulateIntersection in order to create a simple TabulateArea script tool. The TabulateArea script tool will only take polygon features as input.

'''
TabulateArea.py
Description: Shows how to wrap the TabulateIntersection tool to create a TabulateArea script tool
Requirements: Polygon Zone Feature Class, Polygon Class Feature Class

'''
import arcpy
import sys
import os

def AddMsgAndPrint(msg, severity=0):
    # Adds a Message (in case this is run as a tool)
    # and also prints the message to the screen (standard output)
    # 
    print(msg)

    # Split the message on \n first, so that if it's multiple lines, 
    #  a GPMessage will be added for each line
    try:
        for string in msg.split('\n'):
            # Add appropriate geoprocessing message 
            #
            if severity == 0:
                arcpy.AddMessage(string)
            elif severity == 1:
                arcpy.AddWarning(string)
            elif severity == 2:
                arcpy.AddError(string)
    except:
        pass

## Get Parameters
zoneFC = arcpy.GetParameterAsText(0)
zoneFld = arcpy.GetParameterAsText(1) # Only allow one field
classFC = arcpy.GetParameterAsText(2)
outTab = arcpy.GetParameterAsText(3)
classFld = arcpy.GetParameterAsText(4) # Optional and only allow one field
sum_Fields = ""
xy_tol = ""
outUnits = arcpy.GetParameterAsText(5)

## Validate parameters
# Inputs can only be polygons
zoneDesc = arcpy.Describe(zoneFC)
classDesc = arcpy.Describe(classFC)
if zoneDesc.shapeType != "Polygon" or classDesc.shapeType != "Polygon":
    AddMsgAndPrint("Inputs must be of type polygon.", 2)
    sys.exit()
    
# Only one zone field and class field
if zoneFld != "":
    if zoneFld.find(";") > -1 or classFld.find(";") > -1:
        AddMsgAndPrint("A maximum of one zone and/or class field is allowed.", 2)
        sys.exit()

## Run TI with restricted parameters
try:
    arcpy.TabulateIntersection_analysis(zoneFC, zoneFld, classFC, outTab, classFld, sum_Fields, xy_tol, outUnits)
except:
    arcpy.AddMessage("Tabulate Intersection Failed.")
AddMsgAndPrint(arcpy.GetMessages(), 0)


                    

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