Has anyone found an effective ArcGIS 10.3.1 workflow for smoothing streamlines generated from ArcHydro...or hydrology in general?
(Fill -> Flow Dir. -> Flow Acc. -> Stream Def. -> Stream Seg.-> Drainage Line Processing) outputs a polyline that requires manual QA/QC to determine if lines are real and flowing appropriately. Lines look pretty good at 1:1k.
The influence of the source 1 meter DEM becomes more apparent when zooming in.
ArcGIS smooth tool (Advanced Editing toolbar) allows the user to specify a maximum allowable offset. Although you can enter a value between 0 and 1, there does not appear to be any difference between 0.1, 0.2, 0.3, etc. and 1.
ArcToolbox -> Cartography Tools -> Generalization -> Smooth Line tool grants the user the ability to leverage the PAEK or BEZIER INTERPOATION algorithm. PAEK is the default within the editing environment. BEZIER appears better at capturing the far bends or oxbows in a meandering watercourse.
Additionally, Esri help documentation highlights the difference between shapefiles and geodatabase feature classes when smoothing. Only feature classes are capable of true Bezier curves in between adjacent vertices. Shapefiles approximate a curve with multiple straight line segments.
At the moment, I am deriving preliminary stream polylines from a 1 meter bare earth DEM (partially hydro-enforced) with the ArcHydro workflow above. I'm then comparing the output shapes to ancillary surface water data and editing the raster-derived lines manually to add or subtract vertices, so they line up with 6" resolution aerial imagery.
To avoid the jagged line appearance at large scales, my best guess is to:
- Make sure all line editing is taking place on a GDB feature class.
- Utilize Cartography Tools -> Smooth Line tool -> BEZIER_INTERPOLATION
- Ensure close match to aerial imagery by editing the pre-smoothed feature class.
Any other tips for increasing accuracy/efficiency?
Is it possible to make the Smooth tool in the Advanced Editing Toolbar utilize BEZIER INTERPOLATION?