Compute Change Raster (Image Analyst)

Доступно с лицензией Image Analyst.

Краткая информация

Вычисляет абсолютные, относительные или категорийные различия между двумя растрами.

Использование

  • 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 and the pixel values in the To Raster.

      Output = (To Raster) - (From Raster)

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

      Output = (To Raster - From Raster) / max(To Raster, From 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.

  • The output from the Categorical difference computation 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 your 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 analyzing categorical change, the From Raster and To Raster parameter values must both have an associated raster attribute table. The attribute table must have either a VALUE field, CLASS_NAME field, CLASSNAME field, or one string field.

Параметры

ПодписьОписаниеТип данных
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
(Дополнительный)

Specifies the type of calculation to perform 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 in which the output contains class transitions that occurred between the two rasters.
String
From Classes
(Дополнительный)

The list of class names from the From Raster parameter to 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
(Дополнительный)

The list of class names from the To Raster parameter to 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
(Дополнительный)

Specifies the pixels to 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. All pixels that did not change categories will be grouped in a class called Other.
  • Unchanged pixels only —Only the pixels that did not change categories will be categorized in the output. All pixels that changed categories will be groups in a class called Other.
  • All pixels —All pixels will be categorized in the output. This is the default.
String
Transition Class Colors
(Дополнительный)

Specifies the color to use 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.

  • 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

Возвращаемое значение

ПодписьОписаниеТип данных
Output Raster

The output change raster dataset.

Raster

ComputeChangeRaster(from_raster, to_raster, {compute_change_method}, {from_classes}, {to_classes}, {filter_method}, {define_transition_colors})
ИмяОписаниеТип данных
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
(Дополнительный)

Specifies the type of calculation to perform between the two rasters.

  • DIFFERENCEThe mathematical difference, or subtraction, between the pixel values in the rasters will be calculated. This is the default.
  • RELATIVE_DIFFERENCEThe difference in pixel values, accounting for the quantities of the values being compared, will be calculated.
  • CATEGORICAL_DIFFERENCEThe difference between two categorical or thematic rasters will be calculated in which the output contains class transitions that occurred between the two rasters.
String
from_classes
[from_classes,...]
(Дополнительный)

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

This parameter is enabled when the compute_change_method parameter is set to CATEGORICAL_DIFFERENCE.

String
to_classes
[to_classes,...]
(Дополнительный)

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

This parameter is enabled when the compute_change_method parameter is set to CATEGORICAL_DIFFERENCE.

String
filter_method
(Дополнительный)

Specifies the pixels to be categorized in the output raster. This parameter is enabled when the compute_change_method parameter is set to CATEGORICAL_DIFFERENCE.

  • CHANGED_PIXELS_ONLYOnly the pixels that changed categories will be categorized in the output. All pixels that did not change categories will be grouped in a class called Other.
  • UNCHANGED_PIXELS_ONLYOnly the pixels that did not change categories will be categorized in the output. All pixels that changed categories will be groups in a class called Other.
  • ALLAll pixels will be categorized in the output. This is the default.
String
define_transition_colors
(Дополнительный)

Specifies the color to use 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 enabled when the compute_change_method parameter is set to CATEGORICAL_DIFFERENCE.

  • AVERAGEThe color of the output class will be the average of the from (initial) and to (final) class colors. This is the default.
  • FROM_COLORThe color of the output class will match the color of the from (initial) class.
  • TO_COLORThe color of the output class will match the color of the to (final) class.
String

Возвращаемое значение

ИмяОписаниеТип данных
out_raster_dataset

The output change raster dataset.

Raster

Пример кода

ComputeChangeRaster example 1 (Python window)

This example calculates the difference in NDVI pixel values between 2000 and 2020.

# Import system modules
import arcpy
from arcpy.ia import *

# Check out the ArcGIS Image Analyst extension license
arcpy.CheckOutExtension("ImageAnalyst")

NDVIchange = arcpy.ia.ComputeChangeRaster(
	"NDVI_2000.tif", "NDVI_2020.tif", "DIFFERENCE")
	
NDVIchange.save("C:/Data/NDVI_2000_2020.tif")
ComputeChangeRaster example 2 (stand-alone script)

This example calculates the relative difference in NDVI pixel values between 2000 and 2020.

# Import system modules
import arcpy
from arcpy.ia import *

# Check out the ArcGIS Image Analyst extension license
arcpy.CheckOutExtension("ImageAnalyst")

# Define input parameters
FromRaster = "C:/Data/NDVI_2000.tif"
ToRaster = "C:/Data/NDVI_2020.tif"
ChangeType = "RELATIVE_DIFFERENCE"

# Execute - calculate the relative difference in NDVI from 2000 to 2020
NDVIrelativeChange = arcpy.ia.ComputeChangeRaster(
	FromRaster, ToRaster, ChangeType)
	
# Save output
NDVIrelativeChange.save("C:/Data/Relative_NDVI_2000_2020.tif")
ComputeChangeRaster example 3 (stand-alone script)

This example computes the land cover change from 2000 to 2020, extracting only the pixels that changed from the Forest, Agriculture, Water, or Barren classes into Urban.

# Import system modules
import arcpy
from arcpy.ia import *

# Check out the ArcGIS Image Analyst extension license
arcpy.CheckOutExtension("ImageAnalyst")


LandcoverChange = arcpy.ia.ComputeChangeRaster(
	"Landcover_2000.tif", "Landcover_2020.tif", "CATEGORICAL_DIFFERENCE", 
	"'Forest';'Agriculture';'Water';'Barren'", "'Urban'", 
	"CHANGED_PIXELS_ONLY", "AVERAGE")
	
# Save output  
LandcoverChange.save("C:/Data/Landcover_2000_2020.tif")

Информация о лицензиях

  • Basic: Обязательно Image Analyst
  • Standard: Обязательно Image Analyst
  • Advanced: Обязательно Image Analyst

Связанные разделы