Receiver rotations are described by three angles: θ, α and β, as shown in the image below. These rotate from the model coordinates to the fully rotated measurement coordinates . For the rotation matrices associated with these angles, see Key and Lockwood (2010). The θ angle describes the horizontal rotation of the receiver's axis from the 2D model strike direction . For a typical CSEM data set , the data should be rotated so that θ = 0. Therefore, for an array of receivers inline to a horizontal electric dipole source (with transmitter azimuth of 90°), the inline electric field will be the component. There angles α and β describe tilts of the receiver. α is the vertical tilt of the component. If α =0, then β describes the vertical tilt of the , otherwise β describes a slanted angle to .
Key, K., & Lockwood, A. (2010). Determining the orientation of marine CSEM receivers using orthogonal Procrustes rotation analysis. Geophysics, 75(3), F63–F70. doi:10.1190/1.3378765