Data are downloaded (from https://maps.ngdc.noaa.gov/viewers/wcs-client/, by
default) and a string containing the full path to the downloaded file is returned.
Typically, this return value is used with read.topo to read the
data. Subsequent calls to download.topo
with identical parameters will simply return the name of the cached file,
assuming the user has not deleted it in the meantime.
For convenience, if destfile is not
given, then download.topo will construct a filename from the other arguments,
rounding longitude and latitude limits to 0.01 degrees.
download.topo(west, east, south, north, resolution, destdir, destfile,
format, server, debug = getOption("oceDebug"))Longitudes of the western and eastern sides of the box.
Latitudes of the southern and northern sides of the box.
Optional grid spacing, in minutes. If not supplied,
a default value of 4 (corresponding to 7.4km, or 4 nautical
miles) is used. Note that (as of August 2016) the original data are on
a 1-minute grid, which limits the possibilities for resolution.
Optional string indicating the directory in which to store
downloaded files. If not supplied, "." is used, i.e. the data file
is stored in the present working directory.
Optional string indicating the name of the file. If not supplied, the file name is constructed from the other parameters of the function call, so subsequent calls with the same parameters will yield the same result, thus providing the key to the caching scheme.
Optional string indicating the type of file to download. If
not supplied, this defaults to "gmt". See “Details”.
Optional string indicating the server from which to get the data. If not supplied, the default "https://gis.ngdc.noaa.gov/cgi-bin/public/wcs/etopo1.xyz" will be used.
an integer specifying whether debugging information is
to be printed during the processing. This is a general parameter that
is used by many oce functions. Generally, setting debug=0
turns off the printing, while higher values suggest that more information
be printed. If one function calls another, it usually reduces the value of
debug first, so that a user can often obtain deeper debugging
by specifying higher debug values.
String indicating the full pathname to the downloaded file.
All versions of download.topo to date have used a NOAA server as
the data source, but the URL has not been static. A list of the
servers that have been used is provided below,
in hopes that it can help users to make guesses
for server, should download.topo fail because of
a fail to download the data. Another
hint is to look at the source code for
getNOAA.bathy in the marmap package,
which is also forced to track the moving target that is NOAA.
August 2016. http://maps.ngdc.noaa.gov/mapviewer-support/wcs-proxy/wcs.groovy
December 2016. http://mapserver.ngdc.noaa.gov/cgi-bin/public/wcs/etopo1.xyz
June-September 2017. https://gis.ngdc.noaa.gov/cgi-bin/public/wcs/etopo1.xyz
The data are downloaded with download.file, using a URL
devised from reverse engineering web-based queries constructed by
the default server used here. Note that the data source is "etopo1",
which is a 1 arc-second file [1,2].
Three values are permitted for format,
each named after the
targets of menu items on the
NOAA website (as of August 2016): (1) "aaigrid" (for
the menu item "ArcGIS ASCII Grid"), which
yields a text file, (2) "netcdf" (the default,
for the menu item named
"NetCDF"), which yields a NetCDF file
and (3) "gmt" (for the menu item named
"GMT NetCDF"), which yields a NetCDF file in
another format. All of these file formats are
recognized by read.topo.
(The NOAA server has more options, and if
read.topo is extended to handle them, they will
also be added here.)
1. https://www.ngdc.noaa.gov/mgg/global/global.html
2. Amante, C. and B.W. Eakins, 2009. ETOPO1 1 Arc-Minute Global Relief Model: Procedures, Data Sources and Analysis. NOAA Technical Memorandum NESDIS NGDC-24. National Geophysical Data Center, NOAA. doi:10.7289/V5C8276M [access date: Aug 30, 2017].
The work is done with download.file.
Other functions that download files: download.amsr,
download.coastline,
download.met
Other things related to topo data: [[,topo-method,
[[<-,topo-method, as.topo,
plot,topo-method, read.topo,
subset,topo-method,
summary,topo-method,
topo-class, topoInterpolate,
topoWorld
# NOT RUN {
library(oce)
topoFile <- download.topo(west=-64, east=-60, south=43, north=46,
resolution=1, destdir="~/data/topo")
topo <- read.topo(topoFile)
imagep(topo, zlim=c(-400, 400), drawTriangles=TRUE)
data(coastlineWorldFine, package="ocedata")
lines(coastlineWorldFine[["longitude"]], coastlineWorldFine[["latitude"]])
# }
# NOT RUN {
# }
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