I assumed that satellite data would have been enough to know if something was an iceberg or land - wild that new land is still being discovered!
In astronomy the background is mostly static, providing an excellent reference frame either when trying to discover/track a moving object, or when trying to overlap multiple images of the same object for better observations.
If you're looking for an unknown island your background is constantly changing, but you're looking for something which is somewhat static but might not actually exist.