Abstract
Many diving investigations have been carried out and a lot of images, videos etc., have been obtained in the bottom of caldera of Suiyo Seamount. However, the relative positions of each dive are usually uncertain. It is probably due to low accuracy of acoustic positioning in the condition that the caldera bottom is surrounded by walls.
In the JAMSTEC research vessel "NATSUSHIMA" cruise NT03-14, reconstructed positions from detailed video data were compared with SSBL positions, when deep sea hydrophone array system was settled on the sea bottom by ROV "Hyper-Dolphin".
The following conditions are necessary to obtain a position of the sea bottom from the video record.
1. All images are clear and have simple structures.
2. The sea floor is expected to be almost flat.
3. No change in the direction or magnification of the camera image.
4. It is required for the survey line to return to the original point at least once in one trial, or to cross itself.
