NetCDF, one frequency

The same data format for a single frequency. sidescanpy.io.netcdf writes one frequency channel on its own, as a standalone NetCDF-4 file (.nc), without the survey wrapper or the aux records. Use it to hand one frequency to a tool or a colleague that expects a single dataset. For a whole survey, use .ss.h5.

from sidescanpy.io.netcdf import read_frequency_channel, write_frequency_channel

channel = survey.get_frequency("hz_400000")
write_frequency_channel(channel, "line_001_400khz.nc")
channel = read_frequency_channel("line_001_400khz.nc")
channel = read_frequency_channel("line_001_400khz.nc", chunks={"ping": 256})  # lazy

The file holds the same variables and attributes as one frequencies/hz_<Hz> group of an .ss.h5 file, processing_history included, with the same encoding: gzip 4 with shuffle on variables with two or more dimensions, chunks of 256 pings, float64 stored as float32 except latitude and longitude. It reads back identical to what was written, apart from that float32 rounding.

xr.open_dataset("line_001_400khz.nc", engine="h5netcdf") opens it without sidescanpy.