Tonga's uncharted waters reveal surprises in new survey

A new marine navigation chart survey of the waters of Ha‘apai and Nuku‘alofa, has discovered uncharted marine volcanoes that are big enough to sink a cruise ship. Tonga's marine charts, among the oldest still in use, are being updated using airborne laser, metric sonar and an unmanned submarine- enhancing Captain Cook's fathoms measurements made by ropes in the 18th century. By Eleanor Gee.