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Delineate a corridor around a river

Source: R/delineate.R
delineate.Rd

Given a set of delineation parameters and input data, carry out corridor delineation, corridor segmentation and/or riverspace delineation as indicated by the user.

Usage

delineate(
  aoi,
  osm,
  dem = NULL,
  corridor_init = "valley",
  max_iterations = 10,
  capping_method = "shortest-path",
  angle_threshold = 100,
  corridor = TRUE,
  segments = FALSE,
  riverspace = FALSE
)

Arguments

aoi

A list of delineation parameters for an area of interest, namely $city_name, $river_name, $crs, $network_buffer, $dem_buffer, and $buildings_buffer. For more info see define_aoi().

osm

A list with OpenStreetMap data sets within the aoi, as objects of class sf::sfc

dem

Digital elevation model (DEM) of the region (only used if corridor_init is "valley")

corridor_init

How to estimate the initial guess of the river corridor. It can take the following values:

  • "valley": use the river valley boundary, as estimated from a Digital Elevation Model (DEM) (for more info see delineate_valley())

  • numeric or integer: use a buffer region of the given size (in meters) around the river centerline

  • An sf::sf or sf::sfc object: use the given input geometry

max_iterations

Maximum number of iterations employed to refine the corridor edges (see corridor_edge()).

capping_method

The method employed to connect the corridor edge end points (i.e., to "cap" the corridor), as character vector of length one. See cap_corridor() for the available methods.

angle_threshold

Only network edges forming angles above this threshold (in degrees) are considered when forming segment edges. See delineate_segments() and rcoins::stroke(). Only used if segments is TRUE.

corridor

Whether to carry out the corridor delineation

segments

Whether to carry out the corridor segmentation

riverspace

Whether to carry out the riverspace delineation

Value

A list object of class delineation containing zero or more of the following elements: "valley", "corridor", "segments", and "riverspace", each as an sf::sfc_POLYGON or sf::sfc_MULTIPOLYGON object (depending on the geometry of the input data). The list contains only the geometries corresponding to the delineation steps that were carried out (e.g., if segments is FALSE, the list will not contain a "segments" element). In any case, the returned object also contains the base layers and a list aoi with the parameters used for delineation.

Details

The returned delineation class is a list wrapping objects of class sf::sfc_POLYGON or sf::sfc_MULTIPOLYGON which can be retrieved through subsetting and converted to other common spatial classes in typical sf- or terra-based workflows.

Corridor delineation depends on the availability of OpenStreetMap street and railway data around the river. Sparse OSM data, especially too few river crossings, may lead to failed delineation.

Examples

if (FALSE) { # interactive()
# Define delineation parameters within area of interest
aoi <- define_aoi("Bucharest", "Dâmbovița")

# Get data
osm <- get_osm(aoi)
dem <- get_dem(aoi, osm)

# Delineate with defaults
delineate(aoi, osm, dem)

# Carry out all delineations
delineate(aoi, osm, dem, segments = TRUE, riverspace = TRUE)
}