The roads package offers iterative least cost path and minimum spanning tree methods for projecting forest road networks. The methods connect a set of target points to an existing road network using igraph https://igraph.org to identify least cost routes. The cost of constructing a road segment between adjacent pixels is determined by a user supplied weightRaster and a weightFunction; options include the average of adjacent weightRaster values, and a function of the elevation differences between adjacent cells that penalizes steep grades. These road network projection methods are intended for integration into R workflows and modelling frameworks used for forecasting forest change, and can be applied over multiple timesteps without rebuilding a graph at each timestep.

Installation

You can install the released version of roads from CRAN with:

install.packages("roads")

And the development version from GitHub with:

# install.packages("devtools")
devtools::install_github("LandSciTech/roads")

Example

To simulate the development of roads three inputs are needed: the current road network, the locations that should be connected to the road network (landings), and a weights raster that together with the weighting function determines the cost to connect two raster cells with a road. Typically the roads and landings are sf objects or sp Spatial* objects and the weight is a raster.

library(roads)
library(raster)

# data set installed with roads package
demoScen <- prepExData(demoScen)
scen <- demoScen[[1]]

prRoads <- projectRoads(landings = scen$landings.points, 
                        weightRaster = scen$cost.rast,
                        roads = scen$road.line, 
                        plotRoads = TRUE)

By default projectRoads uses an iterative least cost paths algorithm (roadMethod = "ilcp") to connect each landing to the existing road by the lowest cost path, updating the cost after each landing is connected. A minimum spanning tree method (roadMethod = "mst") is also available.

For more details see vignette("roads-vignette", package = "roads")

License

And

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.