R/download.R

In environmentalinformatics-marburg/ESD:

#' Download of NDVI Products
#'
#' @description
#' This function serves as a wrapper around the underlying product-related 
#' download functions. Currently supported datasets originate from the Moderate 
#' Resolution Imaging Spectroradiometer (MODIS) aboard the Terra and Aqua 
#' satellite platforms and the Advanced Very High Resolution Radiometer (AVHRR) 
#' Global Inventory Modeling and Mapping studies (GIMMS).
#'
#' @param type \code{character}. Currently available options are \code{"MODIS"}
#' (default) and \code{"GIMMS"}.
#' @param ... Additional arguments passed to the underlying download functions
#' for MODIS (\code{\link{runGdal}}; see 'Details') and GIMMS data 
#' (\code{\link{downloadGimms}}).
#'
#' @return
#' If \code{type = "GIMMS"}, a \code{character} vector of local filenames. Else 
#' if \code{type = "MODIS"}, a \code{list} of product and date-specific 
#' output files in \code{character} format, see \code{\link{runGdal}}.
#'
#' @details 
#' Note that when working with the MODIS M*D13 product series, the optional 
#' 'SDSstring' argument passed to \code{\link{runGdal}} must at least include 
#' the following four SDS:
#' \itemize{
#' \item{'NDVI' (or 'EVI'), #1 (or #2)}
#' \item{'VI_Quality', #3}
#' \item{'pixel_reliability', #12}
#' \item{'composite_day_of_the_year', #11}
#' }
#' Accordingly, the minimum requirement for 'SDSstring' is \code{"101000000011"} 
#' (\code{"011000000011"}) for the NDVI (EVI).
#' 
#' @author
#' Florian Detsch
#'
#' @seealso
#' \code{\link{runGdal}}, \code{\link{downloadGimms}}.
#'
#' @references 
#' LP DAAC (2016) MOD13Q1: MODIS/Terra Vegetation Indices 16-Day L3 Global 250m 
#' Grid SIN V006. Available online:
#' \url{https://lpdaac.usgs.gov/dataset_discovery/modis/modis_products_table/mod13q1_v006}.
#' 
#' @examples
#' \dontrun{
#' ## Reference extent (Schwaebische Alb)
#' ext <- readRDS(system.file("extdata/alb.rds", package = "ESD"))
#'
#' ## MODIS download
#' mds <- download("MODIS", product = "M*D13A1", collection = "006", 
#'                 extent = ext, begin = "2015001", end = "2015031")
#' mds                 
#'
#' ## GIMMS download
#' gms <- download("GIMMS", x = as.Date("2015-01-01"), y = as.Date("2015-01-31"),
#'                 dsn = paste0(getOption("MODIS_outDirPath"), "NDVI3g.v1_alb"))
#' gms                 
#' }
#'
#' @export download
#' @name download
download <- function(type = c("MODIS", "GIMMS"),
                     ...) {

  if (type[1] == "MODIS") {
    MODIS::runGdal(...)
  } else if (type[1] == "GIMMS") {
    gimms::downloadGimms(...)
  } else {
    stop("Specified product not supported.\n")
  }
}