Pilots, boaters adjust to shift in magnetic north
Ken Kaye, Sun Sentinel
As a result, everyone who uses a compass, even as a backup to modern GPS navigation systems, needs to be aware of the shift, make adjustments or obtain updated charts to ensure they get where they intend to go, authorities say. That includes pilots, boaters and even hikers.
"You could end up a few miles off or a couple hundred miles off, depending how far you're going," said Matthew Brock, a technician with Lauderdale Speedometer and Compass, a Fort Lauderdale company that repairs compasses.
Although the magnetic shift has little impact on the average person and presents no danger to the Earth overall, it is costing the aviation and marine industries millions of dollars to upgrade navigational systems and charts.
Why is magnetic north shifting?
The Earth's core of hot liquid iron is constantly moving. That motion, combined with forces such as the Earth's rotation, dictate the position of magnetic north, not to be confused with geographic north, or the North Pole.
"Magnetic north is shifting all the time; it's a continuous process, not an event," said Jeffrey Love, a geophysicist with the U.S. Geological Survey Geomagnetism Program, based in Golden, Colo.
Over the past century, the shift has been increasing in speed. It went from creeping as slow as nine miles per year in the early 1900s to more than 35 miles per year in the 2000s. However, that acceleration also is part of natural cycle, Love said.
"In 10 to 20 years from now, it might be slowing down," he said.
Currently, the shift creates about a one-degree difference in compass direction every five years, Love said. Accordingly, the Federal Aviation Administration evaluates airport runway numbers every five years, said Kathleen Bergen, FAA spokeswoman.
The FAA could not say how many airports are affected. However, scores of large and small airports in the United States have either changed or plan to change their runways' numbers, which are based on compass directions.
Palm Beach International Airport changed its three runway numbers in December 2009 at a cost of $268,686. That included repainting the runway numbers, replacing signs and updating publications, said airport spokeswoman Casandra Davis.
Feb. 20, 2011