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 in radians. If degrees are desired, the resulting raster must be multiplied by the radianstodegrees conversion factor of 180/pi, or approximately 57.296.
For further assistance, a procedure to follow and some examples of converting output from radians to degrees are available.
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.
