Question

我正在处理MODIS MOD15A2H数据集，并希望将第一层的所有图块合并在一起。我使用gdal_translate（）将.hdf层转换为.tif文件。并尝试使用do.call（merge，tiflist）来合并（see here）。我发现当列表的长度大于5时，单元格的值会发生变化。（更新：我发现与5无关。有时4个文件出错，而其中任意三个文件都运行良好。但是对于其他文件，没有这样的问题。）有人可以帮忙吗？只是不知道为什么以及在哪种情况下..call有这样的问题。

由于没有重叠的问题，我在马赛克中改变了乐趣，因为没有重叠的问题。

#transform to tif
for (i in 1:length(hdffilenames)){
  gdal_translate(sdsnames[i,1], dst_dataset = paste("fpar_",substr(sdsnames[i,1],37,42),".tif",sep = ""))}
tifnames=paste("fpar_",substr(sdsnames[,1],37,42),".tif",sep = "")
h=as.integer(substr(sdsnames[,1],38,39))
subtifnames=list()
for (i in seq(1:36)){
  subtifnames[i]=tifnames[h=i]
}

#merge function
mergetifList <- function(tifList){

  #Internal function to make a list of raster objects from list of files.
  ListRasters <- function(list_names) {
    raster_list <- list() # initialise the list of rasters
    for (i in 1:(length(list_names))){ 
      tif_name <- list_names[i] # list_names contains all the names of the images in .tif format
      raster_file <- raster::raster(tif_name)
      raster_file[raster_file>1] <- NA
    }
    raster_list <- append(raster_list, raster_file) # update raster_list at each iteration
    return(raster_list)
    }

  #convert every raster path to a raster object and create list of the results
  raster.list <-sapply(tifList, FUN = ListRasters)

  # edit settings of the raster list for use in do.call and merge
  names(raster.list) <- NULL
  #####This function deals with overlapping areas
  #raster.list$fun <- max
  #run do call to implement mosaic over the list of raster objects.
  mergeRas <- do.call(raster::merge, raster.list)

  return(mergeRas)
}

然后我使用一些列表进行测试：

 > tifname1=c("fpar_h29v09.tif", "fpar_h29v10.tif", "fpar_h29v11.tif", "fpar_h29v12.tif", "fpar_h29v13.tif")
    > m_1=mergetifList(tifname1)
    > plot(m_1)

see picture here

> tifname2=c
("fpar_h29v08.tif", "fpar_h29v09.tif", "fpar_h29v10.tif", "fpar_h29v11.tif", "fpar_h29v12.tif")
> m_2=mergetifList(tifname2)
> plot(m_2)

see picture here

> tifname3=c("fpar_h29v08.tif", "fpar_h29v09.tif", "fpar_h29v10.tif", "fpar_h29v11.tif", "fpar_h29v12.tif","fpar_h29v13.tif")
> m_3=mergetifList(tifname3)
> plot(m_3)

see picture here

非常感谢！

使用do.call在r中合并大量栅格

0 个答案: