Issues when projecting Flow Direction Raster

[NealBanerjee]

Hello,

Ive noticed that when I try to project a flow direction raster (D8 format) it sometimes changes values of the cells and makes the output flow direction raster not work.  Im keeping same cell size (but switching units).  Im assuming this has something to do when how raster is interpolated (Im using Nearest).  Anyone have idea/suggestion to force values to stay the same?

Thanks

neal

[DanPatterson]

@NealBanerjee  have you gone over the documentation on...

Cell Size Projection Method (Environment setting)—ArcGIS Pro | Documentation

How the Cell Size Projection Method environment setting works—ArcGIS Pro | Documentation

It might give you some insight on your choices given your projection

Addendum.

It might be better to produce the flow direction from a projected DEM first

[NealBanerjee]

Ill check it out - thank you Dan!  Ill post if there is an easy change that "fixes" the issue. Definitely usually would produce directly from DEM, but using the NHD High-Resolution datasets which are quite large so thats why was try to extract area I need.  Thanks again

[DuncanHornby]

Another option is to accept the flow direction grid as-is, generate your catchment polygons and project those? Just an idea.