Preconditioning

Lateral variations

The previous analysis appears 1-dimensional in depth. Conventional interval velocity estimation builds a velocity-depth model independently at each lateral location. Here, we have a logical path for combining measurements from various lateral locations. We can change the regularization to something like $\bold 0\approx \nabla\bold u$ . Instead of merely minimizing the vertical gradient of velocity, we minimize its spatial gradient. Luckily, we have preconditioning and the helix to speed the solution.