The ray-tracing algorithm for 3-D map *de-migration*/migration produces
good results provided that the maximum dip of the layers under investigation
is under the limit corresponding to the chosen velocity model.

The limitation occurs because of the geometrical definition of the method.
This problem drives me to investigate Eikonal equation for time migration
in order to go further in this project. At present time, it is hard to say
whether this new study will provide an algorithm strong enough to perform
*de-migration* and map migration of any kind of time model.

11/17/1997