Electromagnetic (EM) vector sensor arrays can track both the polarisation and direction of arrival (DOA) parameters of the impinging signals. For crossed-dipole linear arrays, due to inherent limitation of the structure, it can only track one DOA parameter and two polarisation parameters. This problem could be solved by extending the geometry to a two-dimensional (2-D) rectangular array so that both the azimuth and elevation angles of the signal can be estimated. In this paper, instead of extending the array to a higher dimension, we replace the crossed-dipoles by tripoles and construct a linear tripole array. It will be shown that such a structure can estimate the 2-D DOA and 2-D polarisation information effectively and a dimension-reduction based MUSIC algorithm is developed so that the 4-D estimation problem can be simplified to two separate 2-D estimation problems, significantly reducing the computational complexity of the solution.