Vector quantisation using successive refinements with codebooks of decreasing dimensions

The invention relates to data processing e.g. compression using vector quantisation, where a sequence of data symbols is represented by a codeword drawn from a codebook according to some mimimum-distortion criterion. The invention concerns construction and use of a set of codebooks of decreasing dimensions, to be used incrementally to determine a vector representation of the data with a direction having an accuracy which satisfies prescribed chordal distortion criteria. Applications include wireless mobile communication networks and positioning systems such as GPS.