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Converting output in radians to degrees for trigonometric tools

Available with Spatial Analyst license.

Available with Image Analyst license.

The output values from certain trigonometric tools are in radians. To convert them to degrees, the values need to be multiplied by a conversion factor of 180/pi, or approximately 57.2958.

In Python, this conversion can be done in the expression directly, or you can define a variable to store the value once and reuse it as needed. Using the ACos tool as an example, the syntax could be in the following form:

>>> import math
>>> from arcpy.sa import *
>>> OutRas = ACos (InRas) * 180.0 / math.pi

Or, you can use a variable for the conversion factor:

>>> import math
>>> rad2deg = 180.0 / math.pi
>>> from arcpy.sa import *
>>> OutRas = ACos (InRas) * rad2deg

The following illustrations demonstrate the results of converting the output values from radians to degrees.

Note:

The variable defined in the example above will be used in these examples.

Examples of converting trigonometric outputs in radians to degrees

Tool

Illustration and Python syntax

ACos
ACos illustration with output converted from Radians to Degrees
OutRas = ACos(InRas) * rad2deg
ASin
ASin illustration with output converted from Radians to Degrees
OutRas = ASin(InRas) * rad2deg
ATan
ATan illustration with output converted from Radians to Degrees
OutRas = ATan(InRas) * rad2deg

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