The stationary-phase approximation used to derive the CAM algorithm
yields constraints in the downward-continuation process that limit
accuracy in imaging, even in 1-D *v*(*z*) media. However, those errors
only become apparent for really steep reflectors (about )with an important cross-line component. CAM is also a more reliable
approximation of the
5-D phase-shift operator than the offset plane-wave algorithm. An even
more robust approximation of the 5-D operator can be the
narrow-azimuth migration algorithm, presently in progress.
Eventually, 1-D media only allow us to estimate errors due to varying
azimuth in downward-continuation. We will address issues related to
multipathing and lateral velocity variations using the SEG/EAGE salt
dome dataset.

4/28/2000