The House has approved spending $581 million over five years to update surveys and charts of heavily traveled waters off the American coast.

The measure passed Wednesday by voice vote is meant to help the National Oceanic and Atmospheric Administration reduce a backlog of 39,000 square nautical miles of "critical areas" where current maps are inadequate or obsolete.The areas include approaches to major ports and waters, primarily off Alaska, that have never been surveyed with modern equipment but have seen increases in traffic by oil tankers, cargo carriers and cruise ships.

Federal spending on coastal surveys was initiated by Thomas Jefferson in 1807 and reached a peak after World War II. But it has declined significantly in the past two decades, and spending amounts have been halved over the past 15 years.

In 1971, NOAA had 11 hydrographic survey ships. Its current fleet totals only three, with the newest built in 1968.