Global surface wave dispersion maps are useful tools for checking the internal consistency of surface wave data that are used int eh modeling of the 3D elastic heterogeneity within the Earth. This paper describes a variety of data that constrain such maps and outlines the modeling techniques that are used to create them. Some reasons why current maps obtained by different workers may still disagree are discussed.
"Resolution issues in global surface wave seismology", Proc. SPIE 4123, Image Reconstruction from Incomplete Data, (16 November 2000); doi: 10.1117/12.409258; https://doi.org/10.1117/12.409258