1. Time-distance Helioseismology Technique Issues T. L. Duvall Jr. (NASA/GSFC)

2. Time-distance analysis: Projection; tracking Filtering (phase speed filtering; other types) Cross correlation (includes mapping; quadrants; deep or surface focusing) ‘peak bagging’ (Gabor wavelet fitting and the Gizon-Birch method) Inversion (somebody else’s problem)

3. Filtering: Phase-speed filtering has a problem: in areas like sunspots with oscillation amplitude spatially varying, travel time errors occur (Rajaguru et al. 2006)

4. Cross correlation:

5. Cross correlation

6. Fitting: Gabor wavelet

7. Fitting: Gizon-Birch method