The Aspen GeoDepth velocity determination and 3D/2D velocity model building system enables explorationists to perform accurate seismic imaging in either time or depth. Through the integration of interpretation, velocity analysis, model building, time-to-depth conversion, depth migrations and model verification and updating, Aspen GeoDepth provides the continuity needed to produce high-quality, interpretable images consistent with other available data, while preventing data loss and honoring geologic constraints.