D8 algorithm to get flow direction in ArcGIS Desktop

Question

I am using ArcGIS 10 for the get the flow direction from DEM. I wonder about the algorithm they have used while calculating flow direction. It is mentioned there that it is using D8 model. D8 model should have the value 1,4,8,16,32,64 and 128. But I am getting the value from 1 to 255. Please correct me if my understanding is not correct.
I want the actual values of D8 model ( 1, 4,8,16,32,64 and 128) in flow direction rather than 1 to 255.
Is it possible to get that value?

A Salim Khan · Answer

The raster you are using is probably an eight bit raster in which the values will range from 1 to 255 regardless of the algorithmic values.

Nxaunxau · Answer

Values other than the D8 values indicate that you have sinks in your DEM. Try the work flow shown here..

http://resources.arcgis.com/en/help/main/10.2/index.html#/Deriving_runoff_characteristics/009z0000005p000000/

D8 algorithm to get flow direction in ArcGIS Desktop

2 Answers

Add your own answers!

Ask a Question