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I have a point shapefile, with each point representing the location of a weather station and storing values for wind SPEED and DIRECTION (in degrees).

My goal is to create a continous surface (raster) for wind direction by interpolating the two wind's components (X and Y) derived using the sine and cosine of the wind direction as described here: http://mmc2.geofisica.unam.mx/cursos/geoest/Articulos/Geostatistics/Non-Linear%20Surface%20Interpolations.htm:

X=H*sin(q)

Y=H*cos(q)

where H is the wind speed, q is the wind direction (in degrees).

I did some web searches, and I found a very good comment from @whuber (Generating wind direction raster using its U and V components in ArcGIS Desktop?), who was suggesting to use the ATan2 function.

Would the following formula (where v and u are the two wind's components, corresponding to the Y and X components in the first cited web source) suffice to achieve the mentioned goal?:

(ATan2(v, u) / (2*3.14159265) + 0.5) * 360
  • For the sine and cosine, you provide them in the units of whatever your function takes. Read the function documentation. – BradHards May 2 '17 at 8:16
  • The formula looks correct to me (I'd use pi to more precision, but that's just me and probably irrelevant given wind direction is normally rounded anyway), but test it to see that you're getting reasonable results. – barrycarter May 3 '17 at 0:20
  • Thank you @barrycarter for your comment. The last formula is actually out from a larger comment, whose math/trigonometric details I cannot always follow. So, I wanted to be sure that that last bit was fit to my general goal. – NewAtGis May 3 '17 at 6:16
  • I am still wondering: if the formula (ATan2(v, u) / (2*3.14159265) + 0.5) * 360 eliminates the need of negating both components (as touched upon here: gis.stackexchange.com/questions/110136/…). I also wonder if the above formula returns the same result as the one (d=atan2(v / u)*180/pi) provided by ArcGIS help to get the direction from components (desktop.arcgis.com/en/arcmap/10.3/manage-data/raster-and-images/…). Any elucidation is welcome. – NewAtGis May 5 '17 at 11:24

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