Get Flowline Index
given an sf point geometry column, return COMID, reachcode, and measure for each.
get_flowline_index( flines, points, search_radius = 0.1, precision = NA, max_matches = 1 )
flines |
sf data.frame of type LINESTRING or MULTILINESTRING including COMID, REACHCODE, ToMeas, and FromMeas. Can be "download_nhdplusv2" and remote nhdplusv2 data will be downloaded for the bounding box surround the submitted points. NOTE: The download option may not work for large areas, use with caution. |
points |
sf or sfc of type POINT |
search_radius |
numeric the distance for the nearest neighbor search to extend. See RANN nn2 documentation for more details. |
precision |
numeric the resolution of measure precision in the output in meters. |
max_matches |
numeric the maximum number of matches to return if multiple are found in search_radius |
Note 1: Inputs are cast into LINESTRINGS. Because of this, the measure output of inputs that are true multipart lines may be in error.
Note 2: This algorithm finds the nearest node in the input flowlines to identify which flowline the point should belong to. As a second pass, it can calculate the measure to greater precision than the nearest flowline geometry node.
Note 3: Offset is returned in units consistent with the projection of the flowlines.
Note 4: See 'dfMaxLength' input to sf::st_segmentize() for details of handling of precision parameter.
data.frame with five columns, id, COMID, REACHCODE, REACH_meas, and offset. id is the row or list element in the point input.
source(system.file("extdata", "sample_flines.R", package = "nhdplusTools"))
get_flowline_index(sample_flines,
sf::st_sfc(sf::st_point(c(-76.87479,
39.48233)),
crs = 4326))
get_flowline_index("download_nhdplusv2",
sf::st_sfc(sf::st_point(c(-76.87479,
39.48233)),
crs = 4326))
get_flowline_index(sample_flines,
sf::st_sfc(sf::st_point(c(-76.87479,
39.48233)),
crs = 4326), precision = 30)
get_flowline_index(sample_flines,
sf::st_sfc(list(sf::st_point(c(-76.86934, 39.49328)),
sf::st_point(c(-76.91711, 39.40884)),
sf::st_point(c(-76.88081, 39.36354))),
crs = 4326),
search_radius = 0.2,
max_matches = 10)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.