In 1996 we began work on the problem of 3 dimensional migration, the process of properly relocating (migrating) radar echoes to their correct geometric location due to effects created by broad-beam antennas. On South Cascade Glacier we collected 31 profile lines parallel to one another separated by 10 meter spacings. We then applied a 3 dimensional migration algorithm to the grid of data, which migrated the data along the axes parallel and perpendicular to the profile lines. The migrated slices were put together in an mpeg movie.
Concerning the movie:
As a part of our migration studies, we have acquired radar profiles over a closely-spaced grid on South Cascade Glacier. Profile lines were spaced every 10 meters, with returns recorded every two meters along each profile, giving a three-dimensional grid of some 4.5 million points. This movie shows a geometrically migrated 'slice' of the glacier along each profile. The visual effect of splicing these profiles into a movie is one of moving 'through' the glacier in the up-flow direction. Watch carefully, and you can see the three-dimensional nature of many of the internal echoes - most probably water bodies and voids within the ice. We are currently working on algorithms that will make the 3-dimensional migration routine more efficient and easy to use.