ATan (Spatial Analyst)

Available with Spatial Analyst license.

Available with Image Analyst license.

Summary

Calculates the inverse tangent of cells in a raster.

Illustration

OutRas = ATan(InRas)

Usage

• In mathematics, all trigonometric functions have a defined range of valid input values called the domain. The output values from each function also has a defined range. For this tool the following are true:

  • The Domain is: -∞ < [in_value] < ∞

  • The Range is: -pi/2 ≤ [out_value] ≤ pi/2

  Note that -∞ and ∞ represent the smallest negative and largest positive value supported by the particular raster format, respectively.

• The input values to this tool are interpreted as unitless.

• Output values are always floating point, regardless of the input data type.

• The output values from this tool are in radians. To use degrees instead, the resulting raster must be multiplied by the radians-to-degrees conversion factor of 180/pi, or approximately 57.296.

  For further assistance, a procedure to follow and examples of converting output in radians to degrees are available.

• If the input is a multiband raster, the output will be a multiband raster. The tool will perform the operation on each band in the input.

• In ArcPy, if the input is a multidimensional raster, all slices from all variables will be processed, and the output will be a multidimensional raster.

• See Analysis environments and Spatial Analyst for additional details on the geoprocessing environments that apply to this tool.

Parameters

Dialog

Label	Explanation	Data Type
Input raster or constant value	The input for which to calculate the inverse tangent values. To use a number as an input for this parameter, the cell size and extent must first be set in the environment.	Raster Layer; Constant

Return Value

Label	Explanation	Data Type
Output raster	The output raster. The values are the inverse tangent of the input values.	Raster

Python

ATan(in_raster_or_constant)

Name	Explanation	Data Type
in_raster_or_constant	The input for which to calculate the inverse tangent values. To use a number as an input for this parameter, the cell size and extent must first be set in the environment.	Raster Layer; Constant

Return Value

Name	Explanation	Data Type
out_raster	The output raster. The values are the inverse tangent of the input values.	Raster

Code sample

ATan example 1 (Python window)

This example calculates the inverse tangent of the values in the input Grid raster.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outATan = ATan("degs")
outATan.save("C:/sapyexamples/output/outatan")

ATan example 2 (stand-alone script)

This example calculates the inverse tangent of the values in the input Grid raster and outputs a TIFF raster.

# Name: ATan_Ex_02.py
# Description: Calculates the inverse tangent of cells in a raster
# Requirements: Spatial Analyst Extension

# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *

# Set environment settings
env.workspace = "C:/sapyexamples/data"

# Set local variables
inRaster = "degs"

# Execute ATan
outATan = ATan(inRaster)

# Save the output 
outATan.save("C:/sapyexamples/output/outatan.tif")

Environments

Auto Commit, Cell Size, Cell Size Projection Method, Current Workspace, Extent, Geographic Transformations, Mask, Output CONFIG Keyword, Output Coordinate System, Scratch Workspace, Snap Raster, Tile Size

Licensing information

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