Package 'pathroutr'

Alaska coastline

Description

Alaska 1:250000 coastal data polygon. This is provided by the Alaska Department of Natural Resources and was obtained from their open data portal (https://gis.data.alaska.gov/datasets/alaska-1250000). Note, only those polygons that intersect with the bounding box of our harbor seal movement are included.

Usage

akcoast

Format

Simple feature collection with 273 features and 5 fields:

geometry

POLYGON

Source

https://gis.data.alaska.gov/datasets/alaska-1250000

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Identify track points that intersect with a barrier polygon

Description

This function identifies the segments of consecutive points that intersect with the barrier polygon feature. The result is a tibble of segment records that identify portions of the track that will need to be re-routed.

Usage

get_barrier_segments(trkpts, barrier)

Arguments

trkpts	Simple Feature points ('sf', 'sfc_POINT'/'sfc_MULTIPOINT') that represent track points. Order is accepted as is and the bounding box of trkpts should be within the bounding box of the barrier polygon.
barrier	Simple Feature polygon ('sf', 'sfc_POLYGON'/'sfc_MULTIPOLYGON') representing the barrier feature. Should be the same barrier as supplied to the prt_visgraph() function.

Value

tibble representing segments of consecutive points that intersect with the barrier feature. the start_pt and end_pt geometry columns represent the bookend points for each segment that do not intersect with the barrier feature. The n_pts column is the number of points to be re-routed.

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land barrier

Description

A polygon dataset used to test and demonstrate package functions for routing paths around barriers

Usage

land_barrier

Format

Simple feature collection with 19 features and 0 fields:

geometry

MULTIPOLYGON

Source

geopackage file available in extData

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points of interest

Description

A point dataset used to test and demonstrate package functions for routing paths around barriers

Usage

poi

Format

Simple feature collection with 67 features and 0 fields:

geometry

MULTIPOINT

Source

geopackage file available in extData

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Extend a path to include given start and end points

Description

This function extends the calculated shortest path to start and end with the provided start_pt and end_pt geometries. This ensures that the final sample of new points along the re-routed path include the portion of the line from the start_pt/end_pt to the nearest network node.

Usage

prt_extend_path(l_geom, start_pt, end_pt)

Arguments

l_geom	geometry passed from inside prt_shortpath()
start_pt	start point
end_pt	end point

Value

linestring

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Find the nearest node for start and end points in segs_tbl

Description

Find the nearest node for start and end points in segs_tbl

Usage

prt_nearestnode(segs_tbl, vis_graph)

Arguments

segs_tbl	output from get_barrier_segments()
vis_graph	sfnetwork output from prt_visgraph()

Value

segs_tbl tibble with updated columns for nearest start and end nodes

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Re-route track points around barrier feature

Description

This is a convenience wrapper, and the suggested function, for re-routing a trkpts series of ordered POINT features around a barrier polygon via vis_graph built with the prt_visgraph() function. The output can be used as a starting point for a custom process to replace the original geometry. Or, provide the output tibble directly to prt_update_points() along with trkpts for simply updating in place.

Usage

prt_reroute(trkpts, barrier, vis_graph, blend = TRUE)

Arguments

trkpts	Simple Feature points ('sf', 'sfc_POINT'/'sfc_MULTIPOINT') that represent track points. Order is accepted as is and the bounding box of trkpts should be within the bounding box of the barrier polygon.
barrier	Simple Feature polygon ('sf', 'sfc_POLYGON'/'sfc_MULTIPOLYGON') representing the barrier feature. Should be the same barrier as supplied to the prt_visgraph() function.
vis_graph	sfnetwork from prt_visgraph()
blend	boolean whether to blend start/end points into network

Details

The blend = TRUE argument will blend all of the start_pt / end_pt geometries in segs_tbl into the vis_graph network via the sfnetworks::st_network_blend() function. This process creates new nodes within vis_graph that are positioned at the perpendicular intersection between each point and the nearest edge. With blend = FALSE the nearest existing node is used. In highly complex coastlines, the use of blend = FALSE could result in re-routed paths that still intersect land or do not accurately represent the intended result. For less complex situations and when computational speed is important, blend = FALSE may be appropriate.

Value

a two-column tibble with column fid representing the row index in trkpts to be replaced by the new geometry in geometry column. If trkpts and barrier do not spatially intersect and empty tibble is returned.

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Calculate the shortest path through a visibility network between two points

Description

Given a segs_tbl tibble created by get_barrier_segments() and a vis_graph created by prt_visgraph(), this function adds a geometry column to segs_tbl that is the shortest path from the POINT geometries provided in the start_pt / end_pt columns of segs_tbl.

Usage

prt_shortpath(segs_tbl, vis_graph, blend = TRUE)

Arguments

segs_tbl	tibble from get_barrier_segments()
vis_graph	sfnetwork from prt_visgraph()
blend	boolean whether to blend start/end points into network

Details

The blend = TRUE argument will blend all of the start_pt / end_pt geometries in segs_tbl into the vis_graph network via the sfnetworks::st_network_blend() function. This process creates new nodes within vis_graph that are positioned at the perpendicular intersection between each point and the nearest edge. With blend = FALSE the nearest existing node is used. In highly complex coastlines, the use of blend = FALSE could result in re-routed paths that still intersect land or do not accurately represent the intended result. For less complex situations and when computational speed is important, blend = FALSE may be appropriate.

This function is typically called directly by prt_reroute and users are discouraged from using this function directly.

Value

segs_tbl data frame with added geometry column for shortest path LINESTRING that connects the start_pt and end_pt coordinates

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Trim tracks to start and end outside barrier

Description

Trim tracks to start and end outside barrier

Usage

prt_trim(trkpts, barrier)

Arguments

trkpts	Simple Feature points ('sf', 'sfc_POINT'/'sfc_MULTIPOINT') that represent track points. Order is accepted as is and the bounding box of trkpts should be within the bounding box of the barrier polygon.
barrier	Simple Feature polygon ('sf', 'sfc_POLYGON'/'sfc_MULTIPOLYGON') representing the barrier feature. Should be the same barrier as supplied to the prt_visgraph() function.

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Update track points with fixed geometry

Description

Original geometry is updated in place and (currently) no record of those points that were updated is provided.

Usage

prt_update_points(rrt_pts, trkpts)

Arguments

rrt_pts	output from prt_reroute() or tibble with rrt_idx and geometry columns
trkpts	original trkpts Simple Features Collection

Value

trkpts with updated geometry

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Create a visibility graph

Description

Create a visibility graph

Usage

prt_visgraph(
  barrier,
  buffer = 0,
  centroids = FALSE,
  centroid_limit = 1e+07,
  aug_points = NULL
)

Arguments

barrier	simple feature 'POLYGON' or 'MULTIPOLYGON' that can be cast into 'POLYGON'
buffer	integer specifying buffer distance for barrier
centroids	logical whether to include centroids in the mesh
centroid_limit	integer minimum size (m^2) for adding centroid to triangles
aug_points	simple feature 'POINT' or 'MULTIPOINT' as additional nodes

Value

sfnetwork

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Spatial predicates

Description

These are custom spatial predicate functions that are negated versions of the spatial predicates st_within(), st-crosses(), and st_intersects

Usage

not_crosses(x, y)

not_within(x, y)

not_intersects(x, y)

Arguments

x, y	simple features.

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