iko because you're relying on the transponder and tracking systems the commercial airplane has. it's not a requirement by the regulations. >> and david souci, the topography of the underwater environment here, do you know much about it? >> i really don't. i have heard it is a fairly smooth topography but it's deep. >> david gallo, that's your expertise mapping on the sea floor. have you mapped to similar topography? what's it like? >> the main feature there is called the southeast indian ridge that runs east to west through the indian ocean. the top of it at about a mile and a half and it slopes off to the north and south an gets down to about three miles. but there's spots on there that can be very rugged. but most of it's fairly gentle volcanic terrain. not the easiest thing to work. but it's something again we're fairly used to. >> as you've said in the past, david gallo, can play tricks with sound which is an issue with the pings that should be coming off the black boxes.