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Download and load GEDI data from the Cloud or local cache

Source: R/chewie-grab.r
grab_gedi.Rd

Download GEDI data from the NASA Earthdata in hdf5 format, convert it to parquet format and load it as an arrow dataset.

Usage

grab_gedi(
  x,
  progress = TRUE,
  timeout = 7200,
  batchsize = 10,
  delete_h5 = TRUE,
  compression = getOption("chewie.parquet.codec")
)

Arguments

x

A chewie.find.x object. dataset. See details.

progress

A logical indicating whether to show a progress bar.

timeout

A numeric indicating the timeout in seconds.

batchsize

A numeric indicating the number of files to download in parallel. where batchsize is less than the number of files to download, the files will be downloaded in chunks of batchsize.

delete_h5

A logical indicating whether to delete the hdf5 file after conversion to parquet. Default is TRUE. these files are saved in getOption("chewie.h5.cache").

compression

A character vector indicating the compression codec to use. Default is getOption("chewie.parquet.codec"). see ?arrow::write_parquet. must be one of: "zstd", "brotli", "gzip", "snappy", "bz2", "lz4", "lzo" or "uncompressed".

Value

An arrow_dplyr_query object.

Details

This function is the main handler for gedi data - it checks the cache to see if the required GEDI data are already downloaded, and if not, downloads them from the NASA Earthdata cloud. Once downloaded each file is converted to parquet format and saved in the cache directory. This saves a huge amount of disk space and enables dynamic reading and filtering of the returned "open" arrow dataset.

{chewie} will only cache specific variables made available in the GEDI hdf5 files. This is in part to reduce disk space but also to improve performance and make working with these data simpler. If you require additional variables to be cached, please raise an issue on the {chewie} GitHub repository.

See also

For more information on the GEDI hdf5 files and the variables they contain see the following links:

1B: https://lpdaac.usgs.gov/documents/585/gedi_l1b_product_data_dictionary_P003_v1.html

2A: https://lpdaac.usgs.gov/documents/982/gedi_l2a_dictionary_P003_v2.html

2B: https://lpdaac.usgs.gov/documents/587/gedi_l2b_dictionary_P001_v1.html

4A: https://daac.ornl.gov/GEDI/guides/GEDI_L4A_AGB_Density_V2_1.html

Examples

if (FALSE) { # interactive()
prairie_creek <- sf::read_sf(
  system.file("geojson", "prairie-creek.geojson", package = "chewie")
)
prairie_creek_find_2b <- find_gedi(prairie_creek,
  gedi_product = "2B",
  date_start = "2022-01-01", date_end = "2022-04-01",
  cache = FALSE
)

prairie_creek_grab_2b <- grab_gedi(
  prairie_creek_find_2b
)
}