gdalcubes (version 0.2.5)

write_ncdf: Export a data cube as a netCDF file

Description

This function will read chunks of a data cube and write them to a single netCDF file. The resulting file uses the enhanced netCDF-4 format (for chunking and compression).

Usage

write_ncdf(
  x,
  fname = tempfile(pattern = "gdalcubes", fileext = ".nc"),
  overwrite = FALSE,
  write_json_descr = FALSE,
  with_VRT = FALSE,
  pack = NULL
)

Arguments

x

a data cube proxy object (class cube)

fname

output file name

overwrite

logical; overwrite output file if it already exists

write_json_descr

logical; write a JSON description of x as additional file

with_VRT

logical; write additional VRT datasets (one per time slice)

pack

reduce output file size by packing values (see Details), defaults to no packing

Value

returns (invisibly) the path of the created netCDF file

Details

The resulting netCDF file contains three dimensions (t, y, x) and bands as variables.

If write_json_descr is TRUE, the function will write an addition file with the same name as the NetCDF file but ".json" suffix. This file includes a serialized description of the input data cube, including all chained data cube operations.

To reduce the size of created files, values can be packed by applying a scale factor and an offset value and using a smaller integer data type for storage. The pack argument can be either NULL (the default), or a list with elements type, scale, offset, and nodata. type can be any of "uint8", "uint16" , "uint32", "int16", or "int32". scale, offset, and nodata must be numeric vectors with length one or length equal to the number of data cube bands (to use different values for different bands). The helper function pack_minmax can be used to derive offset and scale values with maximum precision from minimum and maximum data values on original scale.

See Also

https://www.unidata.ucar.edu/software/netcdf/docs

gdalcubes_set_ncdf_compression

pack_minmax

Examples

# NOT RUN {
# create image collection from example Landsat data only 
# if not already done in other examples
if (!file.exists(file.path(tempdir(), "L8.db"))) {
  L8_files <- list.files(system.file("L8NY18", package = "gdalcubes"),
                         ".TIF", recursive = TRUE, full.names = TRUE)
  create_image_collection(L8_files, "L8_L1TP", file.path(tempdir(), "L8.db")) 
}

L8.col = image_collection(file.path(tempdir(), "L8.db"))
v = cube_view(extent=list(left=388941.2, right=766552.4, 
              bottom=4345299, top=4744931, t0="2018-04", t1="2018-04"),
              srs="EPSG:32618", nx = 497, ny=526, dt="P1M")
write_ncdf(select_bands(raster_cube(L8.col, v), c("B04", "B05")), fname=tempfile(fileext = ".nc"))
# }