nhdplusTools (version 0.7.1)

get_partial_length: Get Partial Flowline Length

Description

Finds the upstream and downstream lengths along a given flowpath (flowline in nhdplus terminology). Internally, the function rescales the reach measure to a flowpath measure and applies that rescaled measure to the length of the flowpath.

Usage

get_partial_length(hl, net = NULL, fl = NULL)

Value

list containing `up` and `dn` elements with numeric length in km.

Arguments

hl

list containing a hydrologic location with names reachcode and reach_meas.

net

data.frame containing a flowpath network with reachcode, frommeas, tomeas, and lengthkm attributes. Not required if `fl` is provided.

fl

data.frame containing one flowline that corresponds to the reachcode and measure of `hl`. Not required if `hl` is provided.

Examples

source(system.file("extdata", "walker_data.R", package = "nhdplusTools"))
hydro_location <- list(comid = 5329339,
                       reachcode = "18050005000078",
                       reach_meas = 30)

(pl <- get_partial_length(hydro_location, walker_flowline))

hydro_location <- sf::st_sf(hydro_location,
                            geom = nhdplusTools::get_hydro_location(data.frame(hydro_location),
                                                                    walker_flowline))

net <- navigate_network(hydro_location,
                        mode = "DM", network = walker_flowline,
                        distance_km = 4, trim_start = TRUE)

plot(sf::st_geometry(walker_flowline[walker_flowline$COMID == hydro_location$comid,]))
plot(sf::st_geometry(hydro_location), add = TRUE)
plot(sf::st_geometry(net), add = TRUE, col = "blue", lwd = 2)

sf::st_length(net)
pl$dn