1. A method for spatial processing of multi-channel measurement data implemented on a control electronics, comprising: measuring multi-channel data with plurality of sensors; estimating by the control electronics from the measured data, by using a Signal Space Separation method, signals representing biomagnetic sources and signals representing sources outside of a sensor area; and presenting, by the control electronics, the estimated signals as multipole moments having orthogonal lead field expressions, resulting in virtual channel data with dissipated measurement geometry data and with less channels than the number of the plurality of sensors.