Create a River Network Object from a Shapefile

Uses readOGR in package 'rgdal' to read a river shapefile, and establishes connectivity of segment endpoints based on spatial proximity.

line2network(path = ".", layer, tolerance = 100, reproject = NULL,
  supplyprojection = NULL)

Arguments

path	File path, default is the current working directory.
layer	Name of the shapefile, without the .shp extension.
tolerance	Snapping tolerance of segment endpoints to determine connectivity. Default is 100, therefore care should be exercised when working with larger units of distance, such as km.
reproject	A valid Proj.4 projection string, if the shapefile is to be re-projected. Re-projection is done using spTransform in package 'sp'.
supplyprojection	A valid Proj.4 projection string, if the input shapefile does not have the projection information attached.

Value

Returns an object of class "rivernetwork" containing all spatial and topological information. See rivernetwork-class.

Note

Since distance can only be calculated using projected coordinates, line2network() will generate an error if a non-projected input shapefile is detected. To resolve this, the shapefile can be re-projected in a GIS environment, or using reproject=, shown in the second example below.

Examples

filepath <- system.file("extdata", package="riverdist")

Gulk_UTM5 <- line2network(path=filepath, layer="Gulk_UTM5")
#> 
#>  Units: m 
plot(Gulk_UTM5)

# # Re-projecting in Alaska Albers Equal Area projection:

AKalbers <- "+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 +towgs84=0,0,0"

Gulk_AKalbers <- line2network(path=filepath, layer="Gulk_UTM5", reproject=AKalbers)
#> 
#>  Units: m 
plot(Gulk_AKalbers)