Surface wave raytracing calculations for periods of 150 to 250 s were performed using the two models of global phase velocity heterogeneity produced by Harvard and CIT, providing a comparison of predicted amplitude and phase anomalies. Theoretical R3/R2 and G3/G2 amplitude asymmetries resulting from focussing and defocussing have similar azimuthal distributions of the more pronounced anomalies for the two structures. The azimuthal patterns of long-period Rayleigh and Love wave phase anomalies about a given source region also resemble one another for the two models. Travel time errors as large as 12 s are accumulated for 200 s period R3 arrivals by neglecting the raypath deviations from great circles: Such errors may be significant when inverting for earth structure or when applying corrections for lateral heterogeneity in source studies.