1. A method comprising: estimating a formation boundary depth from well log data, said well log data providing formation attribute data for a plurality of azimuth angles, wherein said formation boundary depth is estimated for each of said azimuth angles; analyzing effective volume of investigation information to determine an effective depth of investigation (ΔD) and an effective shift in height (Δh) of a formation boundary surface associated with said formation boundary depth; and refining said formation boundary depth estimate using at least one of said effective depth of investigation (ΔD) and said effective shift in height (Δh).