Calculates the inverse tangent (based on x,y) of cells in a raster.
Illustration
OutRas = ATan2(InRas1, InRas2)
Usage
ATan2 converts rectangular coordinates (x,y) to polar (r,θ), where r is the distance from the origin and θ is the angle from the x-axis.
Conversion of rectangular to polar coordinates
The equation for determining ATan2 is: tanθ = y / x (where θ is the angle).
The ATan2 operation represents all quadrants in a Cartesian matrix (based on sign).
The values of the first specified input are used as the numerator in the calculation of the tangent angle (y). The values of the second specified input are used as the denominator in the calculation of the angle (x).
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] < ∞
This domain applies to both inputs.
The Range is: -pi < [out_value] ≤ pi
Note that -∞ and ∞ represent the smallest negative and largest positive value supported by the particular raster format, respectively.
If both input values are 0, the output will be NoData.
If first input value is 0, the output will be 0.
The input values to ATan2 are interpreted as being in linear units, and to give meaningful results, they should both be in the same unit.
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.
If both inputs are single band rasters or one of the inputs is a constant, the output will be a single band raster.
If both inputs are multiband rasters, the tool will perform the operation on each band from one input, and the output will be a multiband raster. The number of bands in each multiband input must be the same.
If one of the inputs is a multiband raster and the other input is a constant, the tool will perform the operation using the constant value for each band in the multiband input, and the output will be a multiband raster.
In ArcPy, if both inputs are multidimensional rasters with the same number of variables, the tool will perform the operation for all slices with the same dimension value, and the output will be a multidimensional raster. The variables in the inputs must have the same dimensions or common dimension but no uncommon dimensions.
If both inputs have one variable but different names, set the matchMultidimensionalVariable geoprocessing environment to False to perform the operation.
In ArcPy, if one of the inputs is a multidimensional raster and the other input is a constant, the tool will perform the operation for all slices for all variables using the constant value, and the output will be a multidimensional raster.
Parameters
Label
Explanation
Data Type
Input raster or constant value 1
The input that specifies the numerator, or y value, to use when calculating the inverse tangent.
A number can be used as an input for this parameter, provided a raster is specified for the other parameter. To specify a number for both inputs, the cell size and extent must first be set in the environment.
Raster Layer; Constant
Input raster or constant value 2
The input that specifies the denominator, or x value, to use when calculating the inverse tangent.
A number can be used as an input for this parameter, provided a raster is specified for the other parameter. To specify a number for both inputs, 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 angle of the input values.
The input that specifies the numerator, or y value, to use when calculating the inverse tangent.
A number can be used as an input for this parameter, provided a raster is specified for the other parameter. To specify a number for both inputs, the cell size and extent must first be set in the environment.
Raster Layer; Constant
in_raster_or_constant2
The input that specifies the denominator, or x value, to use when calculating the inverse tangent.
A number can be used as an input for this parameter, provided a raster is specified for the other parameter. To specify a number for both inputs, 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 angle of the input values.
Raster
Code sample
ATan2 example 1 (Python window)
This example calculates the inverse tangent for two input Grid rasters.
import arcpy
from arcpy import env
from arcpy.ia import *
env.workspace = "C:/iapyexamples/data"
outATan2 = ATan2("degs", "negs")
outATan2.save("C:/iapyexamples/output/outatan2")
ATan2 example 2 (stand-alone script)
This example calculates the inverse tangent for two input Grid rasters.
# Name: ATan2_Ex_02.py
# Description: Calculates the inverse tangent of pixels based
# on (y, x) values from two rasters
# Requirements: Image Analyst Extension
# Import system modules
import arcpy
from arcpy import env
from arcpy.ia import *
# Set environment settings
env.workspace = "C:/iapyexamples/data"
# Set local variables
inRaster1 = "degs"
inRaster2 = "negs"
# Check out the ArcGIS Image Analyst extension license
arcpy.CheckOutExtension("ImageAnalyst")
# Execute ATan2
outATan2 = ATan2(inRaster1, inRaster2)
# Save the output
outATan2.save("C:/iapyexamples/output/outatan2.tif")
