Available with Image Analyst license.
Available with Spatial Analyst license.
Overview
Calculates the inverse tangent (based on x,y) of the pixels in a raster.
Notes
ATan2 function converts rectangular coordinates (x,y) to polar (r,θ), where r is the distance from the origin, and θ is the angle from the xaxis.
The equation for determining ATan2 is as follows:
tanθ = y / x
(where θ is the angle). The ATan2 operation represents all quadrants in a Cartesian matrix (based on sign).The value of the first specified input is used as the numerator in the calculation of the tangent angle (y). The value of the second specified input is 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 have a defined range. For this tool, the domain and range are as follows:
 Domain: ∞ < [in_value] < ∞
 Range: pi < [out_value] ≤ pi
If both input values are 0, the output will be NoData. If the first input value is 0, the output will be 0.
The input values to the ATan2 function are interpreted as being in linear units; to give meaningful results, they should both be in the same unit.
The output raster is always a floatingpoint type, regardless of the input value type.
The output values from this tool are interpreted as unitless.
For further assistance, a procedure to follow, and some examples of converting output from radians to degrees, are available.
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 function 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 function will perform the operation against the constant value for each band in the multiband input, and the output will be a multiband raster.
If both inputs are multidimensional rasters with same number of variables, the function will perform the operation for all slices with same dimension value, and the output will be a multidimensional raster. The variables in the inputs must have same dimensions or a common dimension but no uncommon dimensions.
If one of the inputs is a multidimensional raster and the other input is a constant, the function will perform the operation for all slices for all variables against the constant value, and the output will be a multidimensional raster.
Parameters
Parameter name  Description 

Raster  The input that specifies the numerator, or y value, to use when calculating the inverse tangent. 
Raster2  The input that specifies the denominator, or x value, to use when calculating the inverse tangent. 
Extent Type  Choose which extent should be used in the output raster:

Cellsize Type  Choose which cell size to use in the output raster. If all the input cell sizes are the same, all the options will yield the same results.
