AXISDESCR

AXISDESCR is a metadata keyword used in scientific data files to provide a human‑readable description of the axes of a dataset. It is typically implemented as a string attribute attached to the dataset’s coordinate system within formats such as HDF5, NetCDF or the Unified Soil Model file format. The keyword is not part of the core data array but accompanies the numeric values, enabling software to interpret the meaning and orientation of each axis, for example “latitude”, “longitude”, “pressure level”, or “time”.

The AXISDESCR value is usually a comma‑separated list of short phrases that mirror the order of the coordinate variables. For a 3‑dimensional temperature field stored as temperature(latitude, longitude, pressure), the AXISDESCR might be set to “latitude, longitude, pressure”. When the dataset contains derived or transformed coordinates—such as geographic latitude after regridding—the description should reflect the transformed scale to avoid confusion in downstream analyses.

In practice, calculating an AXISDESCR is straightforward. Developers inspect the coordinate variables declared in the file, capture their descriptive names or units, and concatenate them with commas or another chosen delimiter. For example, in HDF5 one can set the attribute using the HDF5 C API:

```

hid_t dset = H5Dopen(file_id, "/temperature", H5P_DEFAULT);

hid_t attr = H5Acreate1(dset, "AXISDESCR", H5T_C_S1, H5S_ALL, H5P_DEFAULT);

const char *descr = "latitude, longitude, pressure";

H5Awrite(attr, H5T_NATIVE_CHAR, descr);

```

Excelorators of data archives and visualization tools can read AXISDESCR to label plots or to apply axis‑specific operations like rebinning. It also aids in automated metadata checks, allowing scripts to verify that the declared axis names match the actual coordinate variables before performing calculations.

Limitations of AXISDESCR include its reliance on accurate developer input; an incorrect description can propagate misinterpretation. Some communities address this by coupling AXISDESCR with more structured descriptors such as CF conventions or coordinate reference system (CRS) identifiers. Nevertheless, AXISDESCR remains a lightweight, widely adopted mechanism for attaching axis semantics to high‑dimensional scientific datasets, enabling clearer documentation and easier interoperability.