Deep-directional electromagnetic (EM) logging-while-drilling technology can map reservoir boundaries and fluid contacts for strategic geosteering, reservoir navigation, and more recently, for reservoir characterization. The inversion-based resistivity mapping is used to make real-time geosteering decisions and to refine and update the reservoir model during and after drilling. Traditional 1D and 2D inversion approaches ignore the lateral changes of the reservoir, which are contained in the azimuthally sensitive measurements and only provide a longitudinal 2D representation of the 3D reservoir structure around the well. A new 2D lateral imaging inversion uses the full azimuthal sensitivity of the measurements to map the vertical and lateral resistivity heterogeneities around the wellbore. A 2.5D EM solver is run in a Gauss-Newton optimization to reconstruct the measurements in complex scenarios and determine the 2D anisotropic resistivity distribution in an imaging plane along with the orientation of the formation invariant direction with respect to the wellbore. Continuous 2D imaging along the well path generates a 3D reservoir resistivity map in the proximity of the wellbore.