Example script for globcolour chl-a data download

globcolour_download

###################################################
### Download globcolour.info data from ftp site ###
###################################################

# Load libraries
require(raster)
require(tidyverse)

# first request data from https://hermes.acri.fr/index.php?class=archive
# then emailed ftp site address

# define ftp path
url <- "ftp://ftp_hermes:hermes%@ftp.hermes.acri.fr/366819505/"
fn <- RCurl::getURL(url,
                      ftp.use.epsv = FALSE,
                      dirlistonly = TRUE,
                      verbose = F)

# format list of all files
files <- strsplit(fn, "\r*\n")[[1]]
files <- sort(files)

# find files that are merged using GSM algorithm
files <- files[grep("GSM", files)]

# compbine file list with url
url_fn <- paste0(url, files)
url_fn <- sort(url_fn)
url_fn

#Following mdsumner download NSIDC geotiffs to local drive based on required fn
dir.create("globcolour", showWarnings = T)

#Function to get all the files, though avoid re-downloading
download_it <- function(x, path = "globcolour") {
  file <- file.path(path, basename(x))
  if (!file.exists(file)) {
    curl::curl_download(x, file)
    return(TRUE)
  } 
  FALSE
} 

#TRUE if we downloaded it, FALSE if it was already there
test <- purrr::map_lgl(url_fn, download_it)

# test
ncdf4::nc_open(url_fn[1])
ncdf4::nc_open(paste0("globcolour", "/", files[1]))

# ends