nc3tonc41

Usage

Overview

This manual page documents briefly the nc3tonc4 command.

nc3tonc4 is a program that converts a netCDF 3 file into netCDF 4 format, optionally unpacking variables packed as short integers (with scale_factor and add_offset) to floats, and adding zlib compression (with the HDF5 shuffle filter and fletcher32 checksum). Data may also be quantized (truncated) to a specified precision to improve compression.

Options

These programs follow the usual GNU command line syntax, with long options starting with two dashes (`-'). A summary of options is included below.

-h

Shows a summary of the available options.

-o

Overwrite destination file (default is to raise an error if output file already exists).

--vars

A comma separated list of variable names to copy (default is to copy all variables).

--classic=(0|1)

Use NETCDF4_CLASSIC format instead of NETCDF4 (default = 1).

--zlib=(0|1)

Activate (or disable) zlib compression (the default is to activate).

--complevel=(1-9)

Set the zlib compression level (6 is default).

--shuffle=(0|1)

Activate (or disable) the shuffle filter (it is active by default).

--fletcher32=(0|1)

Activate (or disable) the fletcher32 checksum (it is not active by default).

--unpackshort=(0|1)

Unpack short integer variables to float variables using scale_factor and add_offset netCDF variable attributes (it is active by default).

--quantize=(comma separated list of variable name=integer pairs)

Truncate the data in the specified variables to a given decimal precision. For example, 'speed=2, height=-2, temp=0' will cause the variable 'speed' to be truncated to a precision of 0.01, 'height' to a precision of 100 and 'temp' to 1. This can significantly improve compression. The default is not to quantize any of the variables.

--quiet=(0|1)

If set to 1, don't print any diagnostic information.

--chunk=(integer)

The number of records along unlimited dimension to write at once. The default is 10. It is ignored if there is no unlimited dimension. If chunk=0, it means write all the data at once.

--istart=(integer)

The number of the record to start at along unlimited dimension. The default is 0. This option is ignored if there is no unlimited dimension.

--istop=(integer)

The number of the record to stop at along unlimited dimension. The default is 1. This option is ignored if there is no unlimited dimension.