This research deals with increasing the resolution of global earth models by extending the inversion theory to account for non- great circle paths taken by surface waves as a result of the earth's lateral inhomogeneity. The basic theory has been developed by the Principal Investigator and the current work will begin its application and investigate the theory's assumption of non- coupling between modes with models of anisotropy, earth rotation, and lateral heterogeneity. Improved velocity models of the upper mantle are expected to result.