Process MODIS layers

Aggregate layers in a sub-dataset in sinusoidal MODIS products.

Some MODIS products consist of multi-layer subdatasets. This function aggregates multiple layers into single layer SpatRaster. fun_agg is applied at overlapping cells.

Usage

process_flatten_sds(path = NULL, subdataset = NULL, fun_agg = "mean", ...)

Arguments

path: character(1). Full path to MODIS HDF4/HDF5 file. Direct sub-dataset access is supported, for example, HDF4_EOS:EOS_GRID:{filename}:{base_grid_information}:{sub-dataset}
subdataset: character(1). Exact or regular expression filter of sub-dataset. See process_modis_sds for details.
fun_agg: character(1). Function name to aggregate layers. Should be acceptable to terra::tapp.
...: Placeholders.

Value

a SpatRaster object

Note

HDF values are read as original without scaling. Users should consult MODIS product documentation to apply proper scaling factor for post-hoc adjustment. If users have no preliminary information about MODIS sub-datasets, consider running terra::describe(__filename__, sds = TRUE) to navigate the full list of sub-datasets in the input file then consult the documentation of MODIS product.

Author

Insang Song

Examples

## NOTE: Example is wrapped in `\dontrun{}` as function requires a large
##       amount of data which is not included in the package.
if (FALSE) { # \dontrun{
mod09ga_flatten <- process_flatten_sds(
  path =
    list.files("./data", pattern = "MOD09GA.", full.names = TRUE)[1],
  subdataset = process_modis_sds("MOD09GA"),
  fun_agg = "mean"
)
} # }