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 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.

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

Syntax

ATan(in_raster_or_constant)

Parameter	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