Estimating receiver orientation in marine CSEM

A method is provided for determining the orientation of a controlled source electromagnetic receiver. The method comprises forming a linear combination of first and second data records recorded by the receiver for different source positions with substantially equal source-receiver offsets and substantially equal source dipole moments. An orientation angle is selected for which the linear combination has a predetermined characteristic. For example, the linear combination may comprise the sum or difference and the predetermined characteristic may comprise a minimum.