The Structure of the netCDF File

Internally, we use the netCDF format to store STXM 5 data files. The netCDF website is at http://my.unidata.ucar.edu/content/software/netcdf/index.html. IDL has a lot of functions and procedures built in to deal with netCDF files, they all start with ncdf_. Check the IDL help system for details.

We don't describe here how to generally deal with netCDF files in any programming language! This is a list of the contents of the data file:

Dimensions

There are three dimensions in the file, n_fast_pixels, n_slow_pixels and n_data. Their meaning should be obvious.

Datasets

There is one dataset (assigned the three dimensions above) called image_data. It's the raw integer data image_data_intraw as described in Chap. 9. Note that since netCDF doesn't support unsigned integer data types, we store it as signed integers (16 bit), but convert from / to unsigned before writing / after reading.

Global Attributes

Each parameter in sm_par is stored as a global attribute of the same name, except the three that are stored as dimensions (see above). We don't make use of variable attributes.

In case you are wondering where the fast_dist_um and slow_dist_um arrays are: They are not stored directly, but calculated from stage positions and pixel sizes taken from sm_par.