R/internal_ancillary.R

In modisfast: Fast and Efficient Access to MODIS Earth Observation Data

#' @name .getMODIStileNames
#' @aliases .getMODIStileNames
#' @title Get MODIS tile(s) intersecting a given ROI
#' @description Get MODIS tile(s) intersecting a given ROI
#'
#' @inheritParams mf_get_url
#'
#' @return a character string vector with the MODIS tiles intersecting the ROI
#'
#' @details
#'
#' If the ROI is covering multiple MODIS tiles, consider splitting the ROI into multiple parts (1 for each MODIS tile) before executing the \code{mf_get_url} function.
#' Then loop \code{mf_get_url} over each part. Check out the example for some tips on how to proceed.
#'
#' @note
#' The function uses the MODIS tile gridding system available at https://modis.ornl.gov/files/modis_sin.kmz . The same dataset is available in the package through modisfast::modis_tiles
#'
#' @importFrom magrittr %>%
#' @import sf dplyr
#' @noRd



.getMODIStileNames<-function(roi,type){

  . <- Name <- NULL

  .testRoi(roi)

  roi_id <- roi$id

  #modis_tile = sf::read_sf("https://modis.ornl.gov/files/modis_sin.kmz") %>%
  if(type=="modis"){
    tiling_system <- modis_tiles
  } else if (type=="suomi"){
    tiling_system <- suomi_tiles
  }

  sf::st_agr(tiling_system) = "constant"
  sf::st_agr(roi) = "constant"

   roi <- sf::st_transform(roi,4326) %>%
     sf::st_bbox() %>%
     sf::st_as_sfc()

  modis_tile <- tiling_system %>%
    sf::st_intersection(roi) %>%
    dplyr::filter(sf::st_is(., "POLYGON")) %>%
    as.data.frame() %>%
    dplyr::select(Name)

  modis_tile <- modis_tile$Name

    all_modis_tiles <- NULL
    for(i in 1:length(modis_tile)){
    th_modis_tile<-modis_tile[i] %>%
      unique() %>%
      stringr::str_replace_all(c(" "="",":"=""))
    for (i in 1:9){
      th_modis_tile<-gsub(paste0("h",i,"v"),paste0("h0",i,"v"),th_modis_tile)
    }
    if(nchar(th_modis_tile)!=6){
      th_modis_tile<-paste0(substr(th_modis_tile,1,4),"0",substr(th_modis_tile,5,5))
    }
    all_modis_tiles<-c(all_modis_tiles,th_modis_tile)
    }

    roi_id <- rep(roi_id,length(all_modis_tiles))

  return(list(all_modis_tiles = all_modis_tiles, roi_id = roi_id))
}