process_modis_swath: Mosaic MODIS swaths

In amadeus: Accessing and Analyzing Large-Scale Environmental Data

Mosaic MODIS swaths

Description

This function will return a SpatRaster object with values of selected subdatasets. Swath data include curvilinear grids, which require warping/rectifying the original curvilinear grids into rectilinear grids. The function internally warps each of inputs then mosaic the warped images into one large SpatRaster object. Users need to select a subdataset to process. The full path looks like "HDF4_EOS:EOS_SWATH:{file_path}:mod06:subdataset", where file_path is the full path to the hdf file.

Usage

process_modis_swath(
  path = NULL,
  date = NULL,
  subdataset = NULL,
  suffix = ":mod06:",
  resolution = 0.05,
  ...
)

Arguments

path	character. Full paths of hdf files.
date	character(1). Date to query.
subdataset	character. Subdatasets to process. Unlike other preprocessing functions, this argument should specify the exact subdataset name. For example, when using MOD06_L2 product, one may specify c("Cloud_Fraction", "Cloud_Optical_Thickness"), etc. The subdataset names can be found in terra::describe() output.
suffix	character(1). Should be formatted ⁠:{product}:⁠, e.g., ⁠:mod06:⁠
resolution	numeric(1). Resolution of output raster. Unit is degree (decimal degree in WGS84).
...	For internal use.

Value

• a SpatRaster object (crs = "EPSG:4326"): if path is a single file with full specification of subdataset.

• a SpatRaster object (crs = "EPSG:4326"): if path is a list of files. In this case, the returned object will have the maximal extent of multiple warped layers

Author(s)

Insang Song

See Also

• process_modis_warp(), stars::read_stars(), stars::st_warp()

• GDAL HDF4 driver documentation

• terra::describe(): to list the full subdataset list with sds = TRUE

• terra::sprc(), terra::rast()

Examples

## NOTE: Example is wrapped in `\dontrun{}` as function requires a large
##       amount of data which is not included in the package.
## Not run: 
mod06l2_swath <- process_modis_swath(
  path = list.files(
    "./data/mod06l2",
    full.names = TRUE,
    pattern = ".hdf"
  ),
  date = "2024-01-01",
  subdataset = "Cloud_Fraction",
  suffix = ":mod06:",
  resolution = 0.05
)

## End(Not run)

amadeus documentation built on April 4, 2025, 12:21 a.m.