  We propose a method to determine the relative strength of Rashba and
Dresselhaus spin-orbit interaction from transport measurements without the need
of fitting parameters. To this end, we make use of the conductance anisotropy
in narrow quantum wires with respect to the directions of an in-plane magnetic
field, the quantum wire and the crystal orientation. We support our proposal by
numerical calculations of the conductance of quantum wires based on the
Landauer formalism which show the applicability of the method to a wide range
of parameters.
