oce (version 0.9-3)

read.coastline: Scan a coastline data file

Description

Read a coastline file in mapgen, matlab, or Splus format

Usage

read.coastline(file, type=c("R","S","mapgen","shapefile"),
  debug=getOption("oceDebug"), monitor=FALSE, processingLog)
read.coastline.shapefile(file, lonlim=c(-180,180), latlim=c(-90,90),
  debug=getOption("oceDebug"), monitor=FALSE, processingLog)

Arguments

file

name of file containing coastline data.

type

type of file, one of "R", "S", "mapgen" or "shapefile".

debug

set to TRUE to print information about the header, etc.

latlim

range of (signed) latitudes, used only for shapefiles. Regions that do not intersect this range are skipped.

lonlim

as latlim, but a signed longitude.

monitor

print a dot for every coastline segment read (ignored except for reading "shapefile" type)

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.)

Value

• An object of class "coastline", which is a list containing
• data
  a list containing [object Object],[object Object]
• metadata
  a NULL item that may be used in a future version.
• processingLog
  A processingLog of processing, in the standard oce format.

A hack for depth contours

The following demonstrates that this code is getting close to working with depth contours. But this should be handled more internally, and a new object for depth contours should be constructed, of which coastlines could be a subset. library(oce) d <- read.coastline.shapefile("~/Dropbox/DepthContours/DepthContours.shp") isna <- is.na(d[["latitude"]]) idx<-1+cumsum(isna) lat<-split(d[["latitude"]][!isna], idx[!isna]) lon<-split(d[["longitude"]][!isna], idx[!isna]) depths <- d[["depths"]] n <- length(depths) D<-200 plot.window(c(-180,180),c(-90,90), xlab="", ylab="", asp=1) for (i in 1:n) { if (depths[i]==D) lines(lon[[i]],lat[[i]]) }

Details

The S and R formats are identical, and consist of two columns, lon and lat, with land-jump segments separated by lines with two NAs.

The MapGen format is of the form # -b -16.179081 28.553943 -16.244793 28.563330 BUG: the 'arc/info ungenerate' format is not yet understood.

References

The NOAA site http://www.ngdc.noaa.gov/mgg/coast/ is a popular source for coastline data files.

Canadian coastlines in ``shapefile'' format are provided at http://coastalmap.marine.usgs.gov/GISdata/basemaps/canada/shoreline/canada_wvs_geo_wgs84.htm (link tested December 2011) or, with registration, from http://www.geobase.ca/geobase/en/search.do?produit=nrn&language=en (link tested December 2011). The ``shapefile'' format is described in ESRI Shapefile Technical Description, March 1998, available at http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf (link tested December 2011).

See Also

The documentation for coastline-class explains the structure of coastline objects, and also outlines the other functions dealing with them.

Examples

library(oce)
cl <- read.coastline("7404.dat")
# If no plot yet:
plot(cl)
# To add to an existing plot:
lon <- longitude(cl)
lat <- latitude(cl)
lines(lon, lat)
# Note: another trick is to do something like the following,
# to get issues of whether longitude is defined in (-180,180)
# or (0,360)
lines(lon, lat)
lines(lon-360, lat)