Refine Lines, Breaklines & Edges

(Dikes, Thalweg, Streets, Topographic Features)

In many cases provided vector data does not fit the elevation models contours.
Example: Dike path points are given every 25m. If you need points in between, you cannot interpolate linear. The result would be the grey line in Example 1. The interpolation has to consider the related DEM data to produce the much more suitable magenta line in Example 1.

1. Build a corridor with a width w
2. Build new line with fixpoints in a distance
   between dL_min and dl_max
3. Move fixpoints to the highest / lowest point within
   the corridor
   - Using a Relative DEM also allows
   detection of shore lines or slope shoulder
   and feed points
4. Filtering line
   - Automatically tries smoothing with
   splines and other filters
   - Force less sinous lines by virtually
   reducing heights in greater distance:
   User Input: m / 100
   - Prefer points with a strong curvature by
   increasing the curvature factor c
6. Reduce Points and keep a threshold t
Example 1: Dike

Example 2: Ditch

This is the same problem as with dikes. If you interpolate linear to increase the point density, you will cut edges and you will end up with wrong elevation values after mapping.

Example 3: Shorelines (Upper and Lower)

The same technique can also be used to automatically move lines to the shore, bottom or shoulder lines of wider channels, which are very often not clearly visible. I recommend relative elevation models for shoreline detection. Normally the results are way more accurate in flat terrain.

TOP: Relative Elevation Model (used for detection)
BOTTOM: Absolute Elevations (original data)

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