ArcMap

Cell Size Projection Method (Environment setting)

Tools that honor the Cell Size Projection Method environment will use the specified method for calculating the output raster cell size when datasets are projected during analysis.

Learn more about How the Cell Size Projection Method setting works

Usage notes

  • The default Convert units method (CONVERT_UNITS in Python) is equivalent to the method used in previous releases.
  • It is recommended that you specify the cell size projection method appropriate for the analysis.

Dialog syntax

  • Convert units—Units are converted based on the types of coordinate systems involved. When projecting from one projected coordinate system (PCS) to another PCS, linear units are converted by the relevant factor. When transforming from one geographic coordinate system (GCS) to another GCS, angular units are converted. When projecting from GCS to PCS, or PCS to GCS, the output cell size is calculated based on the average of the ratios of the four sides and the two diagonals of the projected extent to the original extent. This is the default.
  • Preserve resolution—The same number of square cells are preserved in the projected extent as are in the original extent. The output cell size is calculated based on the ratios of the areas of the projected extent to the original extent.
  • Center of extent—The center of the original extent is projected to the output coordinate system. The output cell size is calculated by taking the average of the projected distances from the center point to its four adjacent points.

Scripting syntax

arcpy.env.cellSizeProjectionMethod = cellsizeprojectionmethod_option

cellsizeprojectionmethod_optionExplanation

CONVERT_UNITS

Units are converted based on the types of coordinate systems involved. When projecting from one projected coordinate system (PCS) to another PCS, linear units are converted by the relevant factor. When transforming from one geographic coordinate system (GCS) to another GCS, angular units are converted. When projecting from GCS to PCS, or PCS to GCS, the output cell size is calculated based on the average of the ratios of the four sides and the two diagonals of the projected extent to the original extent.

This is the default.

PRESERVE_RESOLUTION

The same number of square cells are preserved in the projected extent as are in the original extent. The output cell size is calculated based on the ratios of the areas of the projected extent to the original extent.

CENTER_OF_EXTENT

The center of the original extent is projected to the output coordinate system. The output cell size is calculated by taking the average of the projected distances from the center point to its four adjacent points.

cellSizeProjectionMethod syntax
import arcpy

# Set the workspace, Output Coordinate System and Cell Size Projection Method environments
arcpy.env.workspace = "C:/workspace"
arcpy.env.outputCoordinateSystem = arcpy.SpatialReference("WGS 1984 UTM Zone 18N")

# Set Cell Size Projection Method environment
arcpy.env.cellSizeProjectionMethod = "PRESERVE_RESOLUTION"

# Set local variables
InZones = "C:/data/parcels.shp"
InZoneField = "Parcel_ID"
InValueRaster = "C:/data/Slope"

# Check out a Spatial Analyst license
arcpy.CheckOutExtension("Spatial")

# Process: Calculate the mean slope of each parcel area.
out = arcpy.sa.ZonalStatistics(InZones, InZoneField, InValueRaster, "MEAN", "DATA")
out.save("mean_ParSlp")

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