# create polyline(s) or polygon(s) represents 100 ft vertical setback from ridgelines

Question asked by williamw on Jun 26, 2017
Latest reply on Dec 21, 2017 by williamw

I am posting this question to the SA Community after I have been working on this on and off. I have yet find a consistent solution and hope someone would share insights to the tools I should look into or methodology that's similar to this case.

The problem - To draw polylines or polygons that represent 100ft vertical setback from the ridges (see 2nd screenshot). My study of area is approx 1500 acres. Here is a screen shot.

This is what I have done thus far after soliciting help from the 3D forum and nearby GIS expert. Thus far, all is running on ArcGIS Pro with both SA and 3D available.

Attempted Method 1:

Semi-manually created 3D ridgelines (as shown in black in the screen shot above, and this is not an issue here, let's ignore why the lines have to be manually edited). In Scene, make 2 copies of a ridgelines and duplicate them 100ft vertically down from the original location. The duplicate lines were placed on either side of the ridge while viewing in 3D. Convert the lines to 3D points (Feature Vertices to Point). Then create contour polyline from the 3D points (Add Geometry Attribute then Points to Line). Build a Terrain Dataset, and use Surface Difference tool to create a polygon. The contour polyline was set to hardline. I played with this method twice at the same location with variance in width (meaning how far apart I placed the duplicated lines) but I yield different result depending on how far of the offset lines I placed.

Attempted Method 2:

Based on Abdullah Anter suggestion from my previous posting. It worked for a small area, but cannot apply to a large area. Because my subtracted ridgeline elevation ranges from 400ft to 1000ft at almost every 10ft interval, using the Contour List essentially create new set of contour of the entire terrain. I could however, convert the new contours to a new raster then intersect the my original and new rasters, but what would be the right tool to create the intersecting lines or areas? Cut/Fill?

BTW, I believe this problem can only be done ridgeline by ridgeline, but I welcome any inputs that can shown me otherwise. Any suggestion on how to create a horizontal warped plane from the ridgeline is welcome, too.

Here is snapshot what the Planners would like to see, a band that traverse along the hillside. Thank you.