ArcMap

Create Accuracy Assessment Points

Available with Spatial Analyst license.

Summary

Creates randomly sampled points for post-classification accuracy assessment.

A common practice is to randomly select hundreds of points and label their classification types by referencing reliable sources, such as field work or human interpretation of high-resolution imagery. The ground truth points are then compared with the classification results at the same locations.

Usage

  • This tool creates a set of random points and assigns a class to them based on ground truth data.

  • This tool can also assign a class to the set of points using a previously classified image or a feature class.

  • After running this tool, you can edit the table if you want to manually assign a class to some or all of the points.

Syntax

CreateAccuracyAssessmentPoints (in_class_data, out_points, {target_field}, {num_random_points}, {sampling})
ParameterExplanationData Type
in_class_data

Input Classification image or other thematic GIS data in raster or feature class format.

Typical data is a classification image (single band, integer data type) or the training polygon output from an ArcMap image classification toolbar.

If using polygons as input, only use those that are not used as training samples. They can also be GIS land-cover data in shapefile or feature class format.

Raster Layer | Feature Layer
out_points

The output point shapefile or feature class that contains the random points to be used for accuracy assessment.

Feature Class
target_field
(Optional)

Choose to have the tool associate a class with each point based on a previously classified dataset or if you want to manually identify each point.

  • CLASSIFIED —Select this option if you want to have the tool assign a class to each point based on an underlying classified image or feature class. This is the default.
  • GROUND_TRUTH —Select this option if you want to manually identify the class associated with each point using high-resolution imagery.
String
num_random_points
(Optional)

The total number of random points that will be generated.

The actual number may exceed but never fall below this number, depending on sampling strategy and number of classes. The default number of randomly generated points is 500.

Long
sampling
(Optional)

Specify a sampling scheme to use.

  • STRATIFIED_RANDOM —Create points that are randomly distributed within each class, where each class has a number of points proportional to its relative area. This is the default
  • EQUALIZED_STRATIFIED_RANDOM —Create points that are randomly distributed within each class, where each class has the same number of points.
  • RANDOM —Create points that are randomly distributed throughout the image.
String

Code sample

CreateAccuracyAssessment example 1 (stand-alone script)

This example creates random points for accuracy assessment.

import arcpy
from arcpy.sa import *

arcpy.gp.CreateAccuracyAssessmentPoints("cls.tif", "aapnt1.shp", "COMPUTED", "1500", "RANDOM")

Environments

Licensing information

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

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