A method for increasing the accuracy of a target property value derived from a rock sample is described in which the sample is scanned to obtain a three-dimensional tomographic digital image which can be processed to pore space and solid material phases through a segmentation process. A process is used which revises the segmented volume, e.g., by increasing pore space connectivity, in a manner affecting the target property value that would be derived. Another described method increases the accuracy with which a segmented volume represents a material sample having structure not adequately resolved in an original three-dimensional tomographic digital image. Further, a system for performing the processes, and a segmented digital volume which more accurately represents a sample of a porous media, are described.