In some embodiments, a method of approximating or determining at least one dimension of at least one underground geological feature in a zone of interest proximate to a well bore includes generating an electric field in the zone of interest while the well bore and geological feature at least partially contain conductive fluid. At least two sensing electrodes are provided in the well bore and configured to detect differences therebetween in electric potential caused by at least one target object in the zone of interest and provide data relating thereto to at least one data processing system. The data processing system(s) approximates or determines the dimension(s) of the geological feature(s) based at least partially upon data provided by the sensing electrodes.