For experts in the field of ocean mapping it is no small irony that we know more about the surfaces of the Moon and Mars than we do about our planet's sea floor."Can you imagine operating on the land without a map, or doing anything without a map?" asked Larry Mayer, director of the U.S.-based Center for Coastal and Ocean Mapping, a research body that trains hydrographers and develops tools for mapping."We depend on having that knowledge of what's around us - and the same is true for the ocean…