Dimension detection

earthkit.transforms makes computations in given domains easier by detecting the dimensions and coordinates of the input data in which it operates. The detection is based on CF conventions, and some additional common identifiers. Users are encouraged to ensure their data is CF compliant to get the best experience.

The dimension/coordinate detection is performed as a first match of the following checks:

1. axis attribute on the data variable or coordinate, e.g. axis = ‘T’ for time. This is a CF convention.

2. standard_name attribute on the coordinate, e.g. standard_name = ‘time’ for time. This is a CF convention.

3. Common variable names for coordinates, e.g. time, latitude, longitude, lat, lon

The following table summarises the identifiers used for dimension/coordinate detection:

Identifier	X (Longitude)	Y (Latitude)	T (Time)	Ensemble
axis attribute	“X”	“Y”	“T”	“E”
standard_name attribute	“projection_x_coordinate”, “longitude”, “grid_longitude”	“projection_y_coordinate”, “latitude”, “grid_latitude”	“time”, “valid_time”, “forecast_reference_time”	“realization”
Common variable names	“lon”, “long”, “longitude”	“lat”, “latitude”	“time”, “valid_time”, “forecast_reference_time”	“ensemble_member”, “ensemble”, “member”, “number”, “realization”, “realisation”