IsoriX (version 0.5)

getelev: Download an elevation raster from internet

Description

The function getelev allows for the download of an elevation raster from internet. It downloads the "Global Multi-resolution Terrain Elevation Data 2010" from our server. The file was orifginally downloaded from: http://topotools.cr.usgs.gov/gmted_viewer/ and converted into a tif file by us. The function getelev uses the generic function downloadfile that can also be used to download directly other files.

Usage

getelev(
	path=NULL,
	overwrite=FALSE,
	verbose=interactive()
	) 
downloadfile(
  address=NULL,
  filename=NULL,
  path=NULL,
  overwrite=FALSE,
  md5sum=NULL,
  verbose=interactive()
)

Arguments

path

A string indicating where to store the file on the hard drive

overwrite

A logical indicating if an existing file should be re-downloaded

verbose

A logical indicating whether information about the progress of the procedure should be displayed or not while the function is running. By default verbose is TRUE if users use an interactive R session and FALSE otherwise. If a numeric is provided instead, additional information about the download will be provided if the number is greater than 1.

address

A string indicating where to download the file from

filename

A string indicating the name of the file to be writen on the disk

md5sum

An optional string indicating the MD5 hashes of the file for testing its integrity

Details

In the argument "path" is not provided, the file will be stored in the current working directory. The functions can create new directories, so you can also indicate a new path. If the package tools is installed, the integrity of the elevation raster is tested after a call to getelev. In case of corruption, try downloading the file again, specifying overwrite=TRUE to overwrite the corrupted file.

Examples

# NOT RUN {
## To download the high resolution
## raster in your current working
## directory, just type:
## getelev()
# }