Conventional horizontal angle domain CIGs are not useful for steeply dipping reflectors because of
the offset stretch.
Reverse-time migration provides robust angle domain CIGs for both steep and near-flat reflectors by merging
horizontal and vertical CIGs. Plane-wave migration in tilted coordinates can also provide
reliable CIGs because the propagation direction is closer to extrapolation direction and the
subsurface offset direction is closer to the dip direction in tilted coordinates.
For both methods, angle domain CIGs of a image point should be viewed in the direction normal to its dip direction.
For the BP velocity benchmark dataset with unrealistically large offsets, comparisons show that reverse-time migration has better large angle energy, otherwise the angle domain CIGs from these two methods are comparable.
When the velocity is not correct, the CIGs from both migration methods provide useful moveout information.
Angle domain common image gathers for steep reflectors