read.coastline.shapefile: Read a coastline File in Shapefile Format

Description

Read coastline data stored in the shapefile format (see reference 1).

Usage

read.coastline.shapefile(
  file,
  lonlim = c(-180, 180),
  latlim = c(-90, 90),
  encoding = NA,
  monitor = FALSE,
  debug = getOption("oceDebug"),
  processingLog
)

Value

x a coastline object.

Arguments

file: name of file containing coastline data (a file ending in .shp) or a zipfile that contains such a file, with a corresponding name. The second scheme is useful for files downloaded from the NaturalEarth website (see reference 2).
lonlim, latlim: numerical vectors specifying the west and east edges (and south and north edges) of a focus window. Coastline polygons that do not intersect the defined box are skipped, which can be useful in narrowing high-resolution world-scale data to a local application.
encoding: ignored.
monitor: Logical indicating whether to print an indication of progress through the file.
debug: set to TRUE to print information about the header, etc.
processingLog: if provided, the action item to be stored in the log. (Typically only provided for internal calls; the default that it provides is better for normal calls by a user.)

A hack for depth contours

The following demonstrates that this code is getting close to working with depth contours. This should be handled more internally, and a new object for depth contours should be constructed, of which coastlines could be a subset.

Author

Dan Kelley

References

The ``shapefile'' format is described in ESRI Shapefile Technical Description, March 1998, available at https://www.esri.com/content/dam/esrisites/sitecore-archive/Files/Pdfs/library/whitepapers/pdfs/shapefile.pdf (last checked 2021-03-24).
The NaturalEarth website https://www.naturalearthdata.com/downloads/ provides coastline datasets in three resolutions, along with similar files lakes and rivers, for borders, etc. It is highly recommended.