Units use in CEASIOMpy are normally given in International System of Units, except if something else is mentioned.
CEASIOMpy is based on the CPACS format. CPACS is an XML file format with allow to define an aircraft geometry and a lot of discipline specific parameters.
The convention used in CEASIOMpy are base on the CPACS conventions
The following values are stored on the CPACS file (at /cpacs/vehicles/aircraft/model/reference) * Reference length: … * Reference area: … * Reference points (x,y,z): …