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Create a Landsat mask raster from the QA band

Source: R/mask_functions.R
landsat_mask_function.Rd

Create a Landsat mask raster from the QA band

Usage

landsat_mask_function(
  raster,
  include = c("land", "water", "both"),
  ...,
  masked_bits
)

Arguments

raster

The QA band of a Landsat image

include

Include pixels that represent land, water, or both? Passing c("land", "water") is identical to passing "both".

...

These dots are for future extensions and must be empty.

masked_bits

Optionally, a list of integer vectors representing the individual bits to mask out. Each vector is converted to an integer representation, and then pixels with matching qa_pixel values are preserved by the mask. Refer to the Landsat science product guide for further information on what bit values represent for your platform of interest.

Value

A boolean raster to be used to mask a Landsat image

Examples

if (FALSE) { # interactive()
aoi <- sf::st_point(c(-74.912131, 44.080410))
aoi <- sf::st_set_crs(sf::st_sfc(aoi), 4326)
aoi <- sf::st_buffer(sf::st_transform(aoi, 5070), 100)

landsat_image <- get_landsat_imagery(
  aoi,
  start_date = "2022-06-01",
  end_date = "2022-08-30",
  mask_function = landsat_mask_function,
  output_file = tempfile(fileext = ".tif")
)

# Or, optionally pass the qa_pixel bits to mask out directly
landsat_image <- get_landsat_imagery(
  aoi,
  start_date = "2022-06-01",
  end_date = "2022-08-30",
  mask_function = \(x) landsat_mask_function(
    x,
    masked_bits = list(c(0:5, 7, 9, 11, 13, 15))
  ),
  output_file = tempfile(fileext = ".tif")
)

# You can use this to specify multiple acceptable values
# from the qa_pixel bitmask; names are optional
landsat_image <- get_landsat_imagery(
  aoi,
  start_date = "2022-06-01",
  end_date = "2022-08-30",
  mask_function = \(x) landsat_mask_function(
    x,
    masked_bits = list(
      clear_land = c(0:5, 7, 9, 11, 13, 15),
      clear_water = c(0:5, 9, 11, 13, 15)
    )
  ),
  output_file = tempfile(fileext = ".tif")
)
}