Hello, I am a graduate student working on a species distribution modeling project and I'm looking for clarification on whether or not I have made the proper calculations. I am utilizing an original Puerto Rico 1-arc-second DEM ESRI file downloaded from NOAA (http://www.ngdc.noaa.gov/dem/squareCellGrid/download/1561), and I am trying to calculate sine and cosine to use as proxies for aspect. ArcGIS helpdesk says the data must be in radians to properly calculate sine and cosine. I ran the tools "sin" and "cos" in ArcMap 10 to obtain the two data sets; however, I stumbled upon this in ArcGIS help (http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009z000000nm000000.htm) stating that if the input you wish to convert are in degrees, you must first transform them into radians. The original DEM is in meters. If the DEM is in meters then what is used to calculate sine and cosine (degrees or radians). I feel that I may not have the properly calculated output.
I need the data (aspect) in linear form as sine and cosine to determine aspect as "northness" (a value from 1 to -1) and "westness" or "eastness" (a value from 1 to -1). There is no tool to transform aspect data from degrees (the tool "aspect" in spatial analyst creates aspect in degrees) to radians to then use the radians data to calculate sine "sin" and cosine "cos". Does anyone have any advice?
