问用栅格软件包下载SRTM数据？

EN

1. ftp://xftp.jrc.it/pub/srtmV4/tiff/FILENAME
2. http://hypersphere.telascience.org/elevation/cgiar_srtm_v4/tiff/zip/FILENAME
3. http://srtm.csi.cgiar.org/SRT-ZIP/SRTM_V41/SRTM_Data_GeoTiff/FILENAME

SRTM<-function(lon, lat) {
  stopifnot(lon >= -180 & lon <= 180)
  stopifnot(lat >= -60 & lat <= 60)
  rs <- raster(nrows=24, ncols=72, xmn=-180, xmx=180, ymn=-60, ymx=60 )
  rowTile <- rowFromY(rs, lat)
  colTile <- colFromX(rs, lon)
  if (rowTile < 10) { rowTile <- paste('0', rowTile, sep='') }
  if (colTile < 10) { colTile <- paste('0', colTile, sep='') }

  f <- paste('srtm_', colTile, '_', rowTile, sep="")
  theurl <- paste("http://srtm.csi.cgiar.org/wp-content/uploads/files/srtm_5x5/TIFF/", f, ".ZIP", sep="")
  utils::download.file(url=theurl, destfile='srtm_40_0.zip', method="auto", quiet = FALSE, mode = "wb", cacheOK = TRUE)
}

SRTM(lon=16, lat=48)

devtools::install_github("pokyah/raster")
library(raster)

# @param country_code.chr a character specifying the ISO contrycode. Ex : BE for belgium
# @param NAME_1.chr a character specifying the NAME_1 value for lower than country level information
# @param aggregation_factor.num a numeric specifying the aggregation factor to get the desired spatial resolution
# @param EPSG.chr a character specifying the EPSG code of the desired Coordiante Reference System (CRS)
# @param path.chr a character specifying the path where to dowload the SRTM data

build_highRes_terrain_rasters.fun <- function(country_code.chr, NAME_1.chr=NULL, aggregation_factor.num=NULL, EPSG.chr=NULL, path.chr) {
  # Path to downloaded SRTM Tiles refs
  srtm.tiles.ref <- raster::shapefile("<PATH_TO_DOWNLOADED_TILES_REFS")

  # Get country geometry first
  extent.sp <- raster::getData('GADM', country=country_code.chr, level=1)

  if(!is.null(NAME_1.chr)){
    extent.sp <- subset(extent.sp, NAME_1 == NAME_1.chr)
  }

  # Intersect extent geometry and tile grid
  intersects <- rgeos::gIntersects(extent.sp, srtm.tiles.ref, byid=T)
  tiles      <- srtm.tiles.ref[intersects[,1],]

  # Download tiles using getData
  # inspired from https://www.gis-blog.com/download-srtm-for-an-entire-country/
  srtm_list  <- list()
  for(i in 1:length(tiles)) {
    lon <- extent(tiles[i,])[1]  + (extent(tiles[i,])[2] - extent(tiles[i,])[1]) / 2
    lat <- extent(tiles[i,])[3]  + (extent(tiles[i,])[4] - extent(tiles[i,])[3]) / 2

    tile <- getData('SRTM', #data are downloaded from http://www.cgiar-csi.org/. See getData do of pokyah/raster repo on github
                    lon=lon,
                    lat=lat,
                    download = FALSE,
                    path = path.chr)

    srtm_list[[i]] <- tile
  }

  # Mosaic tiles
  srtm_list$fun <- mean
  srtm_mosaic.ras <- do.call(raster::mosaic, srtm_list)

  # Crop tiles to extent borders
  extent.elevation.ras <- raster::crop(srtm_mosaic.ras, extent.sp)
  extent.elevation.ras <- raster::mask(extent.elevation.ras, extent.sp)

  # transform to desired CRS
  if(!is.null(EPSG.chr)){
    raster::projectRaster(extent.elevation.ras, crs = toString((dplyr::filter(rgdal::make_EPSG(), code==EPSG.chr))$prj4))
  }

  # aggregate to lower resolution
  # inspired from https://stackoverflow.com/questions/32278825/how-to-change-the-resolution-of-a-raster-layer-in-r
  if(!is.null(aggregation_factor.num)){
    extent.elevation.ras <- raster::aggregate(extent.elevation.ras, fact=aggregation_factor.num)
  }

  # compute the slope from the elevation
  # inspired from https://rpubs.com/etiennebr/visualraster
  extent.slope.ras <- raster::terrain(extent.elevation.ras, opt="slope", unit="degrees")
  extent.aspect.ras <- raster::terrain(extent.elevation.ras, opt="aspect", unit="degrees")
  extent.roughness.ras <- raster::terrain(extent.elevation.ras, opt="roughness")

  # compute the aspect from the elevation
  extent.terrain.ras = raster::stack(
    extent.elevation.ras,
    extent.slope.ras,
    extent.aspect.ras,
    extent.roughness.ras)
}

devtools::install_github("fedefyco/raster")
library(raster)