Is it possible to determine the physical location (e.g. angle + radius) for a particular bit on a CD/DVD/BluRay disk?
The reason I'm asking is this, I want to design a data structure which stores recovery information approximately on the opposite side of the medium to avoid a single scratch from making the whole exercise moot.
CD/DVD/BlueRay encoding schemes include code correction. This is basically another layer of data redundancy which allows the algorithm that decodes the disk to be able to not only detect errors but fix them. When the original engineers and computer scientists decided the encoding schemes for these disks they took scratch resistance into account.
See Reed Solomon codes which are used on CDs/DVDs/BluRay Disks