Calculate Approximate Keylines from Valley or Ridge Networks

Generates approximate keylines by sampling elevation values along main valley or ridge lines and matching them to the nearest pre-computed contour lines.

Important: These keylines are a computational approximation only and should be treated as an orientation for field work. Keylines must always be verified, refined, and adjusted on-site by an experienced practitioner.

Usage

create_keylines(dtm, lines, contours, n_keylines = 3)

Arguments

dtm: A SpatRaster object (terra). The digital elevation model.
lines: A sf or SpatVector object. Either the main valley lines from extract_main_valleys() or the main ridge lines from extract_main_ridges().
contours: A sf or SpatVector object. Pre-computed contour lines with an elevation column named level, typically from calc_geomorph_metrics().
n_keylines: Integer. The desired number of keylines per valley or ridge. Default is 3. Note that the actual number returned may be lower if the input line does not span enough elevation range to support the requested number.

Value

A sf object containing the approximate keylines with the following columns:

level: Elevation of the keyline in map units (usually metres).
line_id: Integer ID identifying which valley or ridge the keyline belongs to.
note: A reminder that these lines are approximations requiring field validation.

Note

Keyline design is a landscape design methodology developed by P.A. Yeomans. The placement of keylines in the field requires expert judgment and cannot be fully automated. This function provides a spatial approximation to support planning and desktop analysis only.

Examples

if (FALSE) { # \dontrun{
# From valley lines
valley_keylines <- create_keylines(dtm, main_valleys, contours, n_keylines = 3)

# From ridge lines
ridge_keylines <- create_keylines(dtm, main_ridges, contours, n_keylines = 3)
} # }