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Climbers try to take most exact measure of Denali's height in history

  • Author: Dermot Cole
    | Opinion
  • Updated: July 7, 2016
  • Published June 25, 2015

In 1910, the head of the computing division of the U.S. Coast and Geodetic Survey offered a detailed set of careful calculations about the height of the biggest mountain in North America, three years before anyone set foot on the summit.

"It is believed that the value (20,300 feet) for the elevation of Mount McKinley is correct within 150 feet," William Bowie wrote in a government report.

We'll soon have a good idea of just how close the early surveyors came to the mark when they took the measure of Denali from afar.

The Denali Summit Survey, a four-member climbing team, is now in the rarefied air with some of the most sophisticated GPS equipment ever made, hoping to return with precise elevation records from the highest point in North America.

It's a tall order with a long history.

When prospector and Princeton man W.A. Dickey proposed the name McKinley in 1897, he said the mountain was probably more than 20,000 feet high, which remains a good guess.

The first to confirm his estimate was geologist Robert Muldrow. In 1901, he wrote in National Geographic that a trip along the "Shushitna River," later spelled Susitna, provided the chance to take measurements of the mountain from six places. His calculations showed heights that ranged from 20,069 feet to 20,874 feet. He offered a "weighted mean" of 20,464 feet, which reigned in mountainous circles until future surveyors chopped off 144 feet.

The astounding thing about the early estimates is not that they differ from the later numbers, but that they are so close. In the 1950s, Bradford Washburn and other experts using the best equipment at the time said the mountain climbed to 20,320 feet.

That number remains popular, though a 1989 expedition with early GPS technology said the mountain topped out at 20,306 feet, a reduction of 14 feet. The 1989 expedition placed a survey monument at the top of the hard-frozen ice that covers the rock.

A 2013 announcement from the state revealed that a radar survey taken as part of a new effort to map Alaska showed that the peak topped out at 20,237 feet, 83 feet shorter than previously thought. At that height, it would still top Mount Logan, the continental runner-up in the Yukon, by nearly 700 feet.

But news stories about Denali shrinkage led to counter-reports that rejected the shrinkage suggestion. The airborne technique that shrank the mountain in 2013 was open to debate and more measuring was needed before an official change, some in the USGS said. And the mountain continues to grow, according to geologists, about 1 millimeter a year, because of the continual grinding of the Pacific and North American plates.

What has never been clear is just how much ice is above the highest rock point on Denali. The Denali Summit Survey is carrying ground-penetrating radar to try and solve that mystery. The amount of snow and ice on top is probably subject to change, so that could explain some of the difference in the mountain's dimensions.

The accuracy of the equipment is another. Several private companies in the mapping world are sponsoring the expedition, along with various government agencies. The climbers include Tom Heinrichs, director of the Geographic Information Network of Alaska, and three others from CompassData.

On Wednesday, two climbers traveled from the 14,000-foot level to the summit and installed GPS antennas and receivers to record data from satellites. "That is a big day of climbing," Heinrichs said in a message posted late that night.

Dave Maune, senior project manager for Dewberry, a Virginia-based engineering firm, said Wednesday the goal is to get measurements that are accurate to less than a centimeter with overnight recordings on top-rate receivers set up to work in the cold.

"Even after we collect the GPS data, it should be a few weeks before we'll know the new elevation of Denali," he said.

"But the question really pertains to what point is surveyed. We cannot reach the rock surface, so I expect we will be surveying a point on top of ice and snow, rather than a survey monument which is otherwise normally mounted in rock," he said.

Among those who look forward to the results is Jeff Yates, an Anchorage climber and photogrammetrist who helped lead the 1989 expedition that determined Denali was 20,306 feet high and placed a survey marker at the summit.

Yates said the pursuit of precision with ever more accurate technology is important not just to climbers, but to all who want to understand more about the world. It's all about refining the work of the past while appreciating the achievements of the early surveyors who narrowed the margin of error.

By any measure, that's progress.

The views expressed here are the writer's own and are not necessarily endorsed by Alaska Dispatch News, which welcomes a broad range of viewpoints.