The concept of polarisation synthesis is based on the mathematical fact that a set of polarimetric measurements in one basis, e.g. H,V, can be converted into any other polarimetric basis, by a mathematical transformation. A basis set is a set of four polarisations. Each set is orthogonal, like LC (left-circular), RC (right-circular). The striking point is that only one set of polarimetric measurements in one basis needs to be recorded and the transformation in other polarimetric bases is done in a post processing step afterwards. There is no need to measure all bases, which is quite complicated in terms of engineering for elliptical and circular polarisation states.