Group acquisitions into time slices.

Adds a slice column (the datetime truncated to granularity); tiles sharing a slice mosaic together in lazy_stac_stack().

Usage

stac_time_slices(
  sources,
  granularity = c("day", "month", "exact", "solar_day"),
  lon = NULL
)

Arguments

sources

A stac_sources() table.

granularity

"day", "month", "exact", or "solar_day".

lon

Longitude (degrees, WGS84) whose solar time defines "solar_day": use the centre of the analysis area. Defaults to the circular mean of the source footprint centres (safe across the antimeridian).

Value

The table with a slice column.

Details

"day" truncates the UTC datetime: one satellite overpass that crosses local midnight in UTC terms splits into two slices. "solar_day" instead shifts each timestamp by a longitude-dependent solar-time offset of lon degrees x 240 s (as used by odc-stac) before taking the date, so acquisitions group by the local day of the overpass; the two agree everywhere except within ~an overpass of the UTC date line at lon.

See also

Other stac helpers: lazy_stac_stack(), stac_drop_duplicates(), stac_filter_assets(), stac_filter_cloud(), stac_filter_coverage(), stac_filter_orbit(), stac_gti_index(), stac_merge(), stac_query(), stac_rename_assets(), stac_sign_mpc(), stac_sources()