xy2segvert: Convert XY Coordinates to River Locations

In riverdist: River Network Distance Computation and Applications

Convert XY Coordinates to River Locations

Description

This function determines the closest vertex in the river network to each point of XY data and returns a list of river locations, defined as segment numbers and vertex numbers.

Usage

xy2segvert(x, y, rivers)

Arguments

x	A vector of x-coordinates to transform
y	A vector of y-coordinates to transform
rivers	The river network object to use

Value

A data frame of river locations, with segment numbers in $seg, vertex numbers in $vert, and the snapping distance for each point in $snapdist. Two additional columns are $snap_x and $snap_y, which give the x- and y-coordinates snapped to the river network.

Note

Conversion to river locations is only valid if the input XY coordinates and river network are in the same projected coordinate system. Point data in geographic coordinates can be projected using sf_project in package 'sf', and an example is shown below.

Author(s)

Matt Tyers

See Also

pointshp2segvert, segvert2xy

Examples

data(Gulk,fakefish)
head(fakefish)

fakefish.riv <- xy2segvert(x=fakefish$x, y=fakefish$y, rivers=Gulk)
head(fakefish.riv)

plot(x=Gulk, xlim=c(862000,882000), ylim=c(6978000,6993000))
points(fakefish$x, fakefish$y, pch=16, col=2)
riverpoints(seg=fakefish.riv$seg, vert=fakefish.riv$vert, rivers=Gulk, pch=15, col=4)


## converting a matrix of points stored in long-lat to Alaska Albers Equal Area:
data(line98, Kenai1)
head(line98)  # note that coordinates are stored in long-lat, NOT lat-long

line98albers <- sf::sf_project(pts=line98, to="+proj=aea +lat_1=55 +lat_2=65 
    +lat_0=50 +lon_0=-154 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs 
    +ellps=GRS80")
head(line98albers)

zoomtoseg(seg=c(162,19), rivers=Kenai1)
points(line98albers)

riverdist documentation built on April 12, 2025, 2:24 a.m.