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ATan

Available with Spatial Analyst license.

Available with Image Analyst license.

Summary

Calculates the inverse tangent of cells in a raster.

Illustration

ATan 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 here -∞ 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. If degrees are desired, 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 some examples of converting output in radians to degrees are available.

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

Syntax

ATan (in_raster_or_constant)
ParameterExplanationData Type
in_raster_or_constant

The input for which to calculate the inverse tangent values.

In order 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

NameExplanationData 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")

Licensing information

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

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