Flip Streams

Ensures that stream linestrings are oriented in an upstream direction, i.e., that the start (mouth) of each linestring is lower than its end. The elevations of the start and end of each linestring are obtained using fwa_add_elevatr_elevation_to_point() or fwa_add_gm_elevation_to_point() and linestrings whose start is more than min_difference m higher than their end are reversed. All other linestrings are not altered.

Usage

fwa_flip_streams(x, source = NULL, zoom = 12, min_difference = 5)

Arguments

x

An sf tibble with a column blk and linestrings of streams (or stream segments).

source

A string of the source of the elevations. Possible values are "elevatr" (no API key required) and "google" (requires a Google Maps Elevation API key). If NULL (the default) "google" is used but this is and source should be set explicitly.

zoom

A whole number between 1 and 14 of the zoom level of the Terrain Tiles. Higher zoom levels have a finer resolution but take longer to download. Ignored if source = "google".

min_difference

A non-negative number of the minimum difference (m) between the elevations of the start and end of a linestring for it to be reversed.

Value

A copy of x with the linestrings oriented upstream.

See also

fwa_add_elevatr_elevation_to_point(), fwa_add_gm_elevation_to_point() and fwa_join_stream_segments()

Examples

if (FALSE) { # \dontrun{
watershed <- fwa_add_watershed_to_blk(data.frame(blk = 356308001, rm = 1000))
network <- fwa_add_collection_to_polygon(watershed)
network <- select(network, blk = blue_line_key)
fwa_flip_streams(network)
} # }