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Compute Change Raster (Image Analyst Tools)

Summary

Calculates the absolute, relative, categorical, or spectral difference between two raster datasets.

Usage

  • This tool compares two rasters and generates a new raster containing the difference between the two. For example, use this tool to find out how carbon storage pixel values have changed between 2001 and 2020 or to see how land cover has changed from 2010 to 2015.

  • The following calculation types are available to compute the change raster:

    • Difference—The mathematical difference, or subtraction, between the pixel values in the From Raster parameter and the pixel values in the To Raster parameter.

      \(Output \space = \space (To \space Raster) \space - \space (From \space Raster)\)

    • Relative difference—The difference in pixel values accounting for the quantities of the values being compared.

      \(Output \space = \space (To \space Raster \space - \space From \space Raster) \space / \space max(To \space Raster, \space From \space Raster)\)

    • Categorical difference—The difference between two categorical or thematic rasters in which the output shows every class transition that occurred between the two rasters.

    • Spectral Euclidean Distance—The Euclidean distance between two multiband rasters, where each pixel is treated as a vector. Larger values indicate more change between the images.

    • Spectral Angle Difference—The spectral angle between two multiband rasters, where each pixel is treated as a vector. Larger angles indicate more change between the images.

    • Band With Most Change—The band that accounts for the most change in each pixel between two multiband rasters.

  • The output from the Categorical difference calculation type is a raster dataset with an attribute table. The table contains the transition types (for example, Forest to Urban), the number of pixels included in each transition type, and the estimated area of each transition type. Area is calculated as the pixel size multiplied by the number of pixels in each transition type. The units match the linear units of the input raster data.

  • You can limit the analysis to specific classes when computing the difference between two categorical rasters. For example, to visualize urban growth, you can include all the classes in the From Classes list, but only the Urban class in the To Classes list. The result will contain all of the transitions that contributed to the Urban category.

  • If the input rasters contain different cell sizes or extents, you can specify the cell size and extent in the Cell Size and Output Extent environment settings.

  • When the Compute Change Method parameter is set to Categorial difference, the From Raster and To Raster parameters must have an associated raster attribute table with a Value or ClassValue field. The class names for the corresponding class values are used for the output class transmission names. The tool uses the standard field class names CLASS_NAME or CLASSNAME. If these field names do not exist, you can use the Classname Field for From Raster and Classname Field for To Raster parameters to define them.

Parameters

Label Explanation Data type

From Raster

The initial or earlier raster to be analyzed.

Raster Dataset; Raster Layer; Mosaic Dataset; Mosaic Layer; Image Service; String

To Raster

The final or later raster to be analyzed. This is the raster that will be compared to the initial raster.

Raster Dataset; Raster Layer; Mosaic Dataset; Mosaic Layer; Image Service; String

Compute Change Method

(Optional)

Specifies the type of calculation that will be performed between the two rasters.

  • Difference—The mathematical difference, or subtraction, between the pixel values in the rasters will be calculated. This is the default.

  • Relative difference—The difference in pixel values, accounting for the quantities of the values being compared, will be calculated.

  • Categorical difference—The difference between two categorical or thematic rasters will be calculated. The output will contain class transitions that occurred between the two rasters.

  • Spectral Euclidean distance—The Euclidean distance between the pixel values of two multiband rasters will be calculated.

  • Spectral angle difference—The spectral angle between the pixel values of two multiband rasters will be calculated. The output is in radians.

  • Band with most change—The band that accounts for the most change in each pixel between two multiband rasters will be calculated.

String

From Classes

(Optional)

The list of class names from the From Raster parameter that will be included in the computation. If no classes are provided, all classes will be included.

This parameter is active when the Compute Change Method parameter is set to Categorical difference.

String

To Classes

(Optional)

The list of class names from the To Raster parameter that will be included in the computation. If no classes are provided, all classes will be included.

This parameter is active when the Compute Change Method parameter is set to Categorical difference.

String

Filter Method

(Optional)

Specifies the pixels that will be categorized in the output raster. This parameter is active when the Compute Change Method parameter is set to Categorical difference.

  • Changed pixels only—Only the pixels that changed categories will be categorized in the output. Pixels that did not change categories will be grouped in a class called No Change.

  • Unchanged pixels only—Only the pixels that did not change categories will be categorized in the output. Pixels that changed categories will be grouped in a class called No Change.

  • All pixels—All pixels will be categorized in the output. This is the default.

String

Transition Class Colors

(Optional)

Specifies the color that will be used to symbolize the output classes. When a pixel changes from one class type to another, the output pixel color represents the initial class type, the final class type, or a blend of the two.

This parameter is active when the Compute Change Method parameter is set to Categorical difference.

  • Average From and To colors—The color of the output class will be the average of the from (initial) and to (final) class colors. This is the default.

  • From color—The color of the output class will match the color of the from (initial) class.

  • To color—The color of the output class will match the color of the to (final) class.

String

Classname Field for From Raster

(Optional)

The field that will store class names in the From Raster parameter value. The tool automatically searches for the ClassName field or Class_Name field to use.

Use this parameter if the input does not contain these standard field names.

Field

Classname Field for To Raster

(Optional)

The field that will store class names in the To Raster parameter value. The tool will automatically search for the ClassName field or Class_Name field to use.

Use this parameter if the input does not contain these standard field names.

Field

Return value

Label Explanation Data type

Output Raster

The output change raster dataset.

Raster

Environments

Cell Alignment, Cell Size, Compression, Current Workspace, Extent, Geographic Transformations, NoData, Output CONFIG Keyword, Output Coordinate System, Parallel Processing Factor, Pyramid, Raster Statistics, Resampling Method, Scratch Workspace, Snap Raster, Tile Size

Licensing information

  • Basic: Requires Image Analyst
  • Standard: Requires Image Analyst
  • Advanced: Requires Image Analyst