about these pingers that are in the ocean. this is such a difficult search because you are talking about underwater. we think about ground robots. this is under water. we are dealing with ground robots. they are talking about two dimensions. when you talk about under the water, this is truly a three dimensional search. >> that's right. depending upon, obviously the strength of the battery and age of the black box and pinger, the range is between a half mile all the way up to three miles or perhaps beyond. that is from the ocean floor up and then the side distance, too. you are working off angles no matter how you cut it. given it is only at maximum, a three-mile radius. that is pretty close to the surface, which it would not be. if it is a pinger, they have a pretty good fix on the location.