INTRODUCTION

 There are many reasons for cutting data planes or image planes into pieces (patches), operating on the pieces, and then putting them back together again. The earth's dip varies with lateral location and depth. The dip spectrum and spatial spectrum thus also varies. The dip itself is important in all earth mapping, and its spectrum plays an important role (inverse covariance matrix) in estimating any earth properties. Chapter 4 of PVI Claerbout (1992) shows code to handle nonstationarity and uses it for dip estimation. There I did not acknowledge the conjugacy aspect of parceling data into patches (small planes). Additionally, now having significantly more experience with nonstationarity, I revise the general looping procedure and repackage code in more reusable form. The utility code here should have many applications. (I am planning uses related to monoplane-rejection regression and other 2-D prediction-error filters.)