# ATan (Spatial Analyst)

Available with Spatial Analyst license.

Available with Image Analyst license.

## Summary

Calculates the inverse tangent of cells in a raster.

## 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")``````

## Licensing information

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