filter

Filter a produced Parquet data file by a geographic bounding box, keeping or dropping whole profiles, and write the result to a new Parquet file.

ctddump filter [--mode include|exclude] \
  --min-lon <W> --max-lon <E> --min-lat <S> --max-lat <N> \
  <src.parquet> <dest.parquet>

The box is inclusive on all four edges, and --min-* must not exceed the matching --max-* (an inverted box is rejected; antimeridian wrap is not supported).

Because a profile’s longitude/latitude are constant across its observations, the box acts on whole profiles, every observation of a matching profile is kept or dropped together.

--mode (default include):

A profile whose position is NaN (unknown) is treated as outside the box: dropped by include, kept by exclude.

The file is streamed one row group at a time, so peak memory stays bounded regardless of file size (tune with CTDDUMP_CHUNK_ROWS, as for convert).

# Keep only profiles inside a Mediterranean sub-box
ctddump filter \
  --min-lon 5 --max-lon 15 --min-lat 35 --max-lat 40 \
  merged.parquet med_box.parquet

# Remove profiles inside that box, keep the rest
ctddump filter --mode exclude \
  --min-lon 5 --max-lon 15 --min-lat 35 --max-lat 40 \
  merged.parquet outside_box.parquet