R/DownloadSentinel2.R

In mcgregorian1/cgaR: A way to share common functions from CGA

#' Download Sentinel 2 dataset from google cloud.
#'
#' This function requires Google Cloud Storage SDK, you can download and install this SDK
#' from google cloud website: https://cloud.google.com/sdk/install and make sure the system PATH is set 
#' so you can use 'gsutil' tool directly in command line.
#' 
#' And just to notice. Most L2A data is only available after 2018, if you want to use L2A before 2018, you need to download L1C data and do the atmophere correction using sen2cor yourself.
#' You can search if there is L2A data available in your study area using website: https://scihub.copernicus.eu/dhus/#/home , but that website doesn't support batch downloading, and download data 
#' from there is much more slower than from google cloud.
#' 
#' Once it started, press ctrl+c in the command line can stop it.
#'
#' If there's any bug, please let me know.
#'
#' Author: Jacory
#'
#' @param tilename what tile do you want to download
#' @param folder local folder used to store downloaded files
#' @param L2Flag indicate to download L2A product or L1C product (default)
#' @param regExp regular expression, (default is NULL) with which you can specify which files you want. Be really careful to use this. For example,
#' regExp <- "S2\\D_MSIL\\d\\D_201([6]|[8][0][0-9]).*.SAFE/$" means you want the whole year data of 2016 and data from Jan to Sep of 2018.
#' @keywords sentinel
#' @export
#' @examples
#' DownloadSentinel2("17SNA", "D:/", L2Flag = TRUE, regExp = "S2\\D_MSIL\\d\\D_201([6]|[8][0][0-9]).*.SAFE/$")
DownloadSentinel2 <- function(tilename, folder, L2Flag = FALSE, regExp = NULL) {
    gcUrl <- ifelse(L2Flag == TRUE, file.path("gs://gcp-public-data-sentinel-2/L2/tiles", substr(tilename, 1, 2),
                                        substr(tilename, 3, 3), substr(tilename, 4, 5)),
                                    file.path("gs://gcp-public-data-sentinel-2/tiles", substr(tilename, 1, 2),
                                        substr(tilename, 3, 3), substr(tilename, 4, 5)))
    com <- paste("gsutil ls", gcUrl)
    fileList <- system(com, intern = TRUE) # View(fileList)
    # create destination folder
    destDir <- folder
    if (dir.exists(file.path(destDir, tilename)) == FALSE) dir.create(file.path(destDir, tilename))

    # regular expression filter
    if (!is.null(regExp)) fileList <- grep(regExp, fileList, value = TRUE)

    # check if there is data matching the search
    if (identical(fileList, character(0)) | length(fileList) == 0) {
        print("Didn't find any data matching the search!")
        return(NULL)
    }

    # started downloading
    for (i in 1:length(fileList)) {
        temp <- unlist(strsplit(fileList[i], "/"))
        dirname <- temp[length(temp)]
        if (dir.exists(file.path(destDir, tilename, dirname)) == FALSE) {
            system(paste("gsutil -m cp -r", fileList[i], file.path(destDir, tilename, ".")))
        }
    }
}