Why I got other values aside from the eight valid output directions when applying flow direction to elevation raster cells?

VannarySeng

Hi, I am using ArcGIS Pro 2.9.0. I would like to know why I got other values aside from the eight output directions (1,2,4,8,16,32,64,128) when I applied the flow direction tool to my elevation raster cell (DEM). I used the sink function to see whether those values correspond to sinks. It seems that was not the case. However, It output correctly if I used the fill tool on my elevation raster cell before applying it to the flow direction tool.  

I would like to know what the other values mean and how to get the correct flow direction output without using the fill tool because I would like to keep the depression points in my raster. 

Thank you

 

Luke_Pinner

What flow modeling algorithm did you specify?

D-Infinity (DINF) output is angle in degrees going counter-clockwise from 0 (due east) to 360 (due east), not the D8 direction codes (1,2,4,8,16,32,64,128).