North America's tallest peak, Mount McKinley in Alaska, just got shorter, according to new maps published by the official U.S. geographers.
New technology used by the U.S. Geological Survey found that Mount McKinley, also known as Denali, tops out at 20,237 feet (6,168 metres) - short of the 20,320 feet (6,193 metres) commonly cited as the summit elevation.
The USGS elevation data was part of a series of about 400 updated maps released earlier in September by the agency, which is updating and refining all of Alaska's topographic maps, some of which have been used for decades.
For years, mountain climbers, aviators and others have relied on the published 20,320-foot measurement for the mountain because that was on topographic maps, the product of a 1952 geographic measurement.
That has been considered the "published" elevation, said Becci Anderson, a geographer who serves as the USGS' Alaska regional geospatial liaison.
The new data came from a 2012 survey that employed Interferometric Synthetic Aperture Radar, or IFSAR, a technology designed to track digitally very small geographic forms and changes that might be taking place.
Different methods of compilation may account for the change in measured elevation, along with other possible factors, including advancements in technology and even climate, the USGS said on its website.
While the new radar-compiled data shows a difference between the 1952 measurement and the new measurement, the USGS "takes no position in favor of either elevation," the agency said.
The new 23,237-foot summit measurement is actually the second revision issued since 1952. Mapping in 1989, which used then-new GPS technology, found the mountain to have a summit elevation of 20,306 feet (6,189 metres). But that figure was not considered published because it was not on topographic maps, Anderson said.
But there is more to the story than shrinkage of the famous mountain, Alaska Lieutenant Governor Mead Treadwell said in a statement on Wednesday.
The mapping initiative added into the database an entire ridge of a nearby mountain, Mount Dickey, Treadwell said. That ridgeline had been omitted from previous documents.