Rising more than 20,000 feet above sea level, Denali is the highest peak in North America. But here鈥檚 the thing: Nobody knows exactly how high it is.聽
Three weeks ago, a group of climbers headed to the mountain to answer this question. They鈥檙e part of a 聽led by the University of Alaska聽Fairbanks聽and survey company 聽and funded by various governmental agencies, including the U.S. Geological Survey and the National Oceanic and Atmospheric Administration, to put an end to the controversy once and for all.聽
鈥淚t just seemed crazy to me that we don鈥檛 know the elevation of the highest mountain in the U.S. It鈥檚 disputed by more than 23 meters [or 75 feet], which is a lot,鈥� says Blaine Horner, a former Denali guide and one of the climbers from CompassData.聽
It鈥檚 not like groups haven鈥檛 tried to come up with an exact height before. Many have, but they鈥檝e all arrived at different numbers, using old, disputed technology. The widely accepted elevation of Denali (20,320 feet) is based on a survey Bradford Washburn completed in 1953. Since GPS wasn鈥檛 a thing back then, he used a process called photogrammetry, which relies on aerial photography, to figure out the mountain鈥檚 height.
Thirty-six years later, another group used an early version of GPS to measure the mountain. They came up with an elevation of 20,306 feet. Then, in 2013, another survey outfitted a plane with remote sensors, flew聽over the peak, and pegged the height at 20,237 feet. (That鈥檚 the stated elevation you鈥檒l find if you search Wikipedia.)
鈥淚t just seemed crazy to me that we don鈥檛 know the elevation of the highest mountain in the U.S. It鈥檚 disputed by more than 75 feet, which is a lot,鈥� says Blaine Horner.
The 2015 project differs from both the 1953 and 2013 surveys because it鈥檚 sending climbers to the summit. 鈥淲ith our project, we actually had boots on the ground,鈥� Horner says. 鈥淚f you come over the south side of Denali in a plane, you have this insane vertical relief, and it鈥檚 going to be pretty hard for any sensor to keep up with that.鈥� This survey will also be more accurate than the 1989 mission because there are more (and more accurate) satellites for the survey equipment to communicate with.
Ten days after Horner and his colleague Agustin Karriere arrived at base camp, the pair summited and began taking measurements. (Two others on the team remained at 14,200 feet in a support role.)聽It was a clear day, zero degrees, and no wind鈥攂almy as far as Denali summit days go.聽
They set up two different pieces of survey equipment鈥攁 Trimble NetR9 and a Trimble R10鈥攖o measure the exact location and elevation of the summit. One device was placed at the true summit; the other was set 2.5 meters back, but with its antenna at the same height as the first to get the same elevation. Both devices measured the summit鈥檚 location and elevation by accessing satellites from three different groups: GPS, the Russian version of GPS called GLONASS, and another group of satellites called QZSS.聽
The two receivers communicated with the satellites. By figuring out their distance from a group of satellites, the receivers determined their exact location on the ground. The results should be accurate down to the centimeter.
Because batteries tend to die in the cold, Horner and Karriere hooked up each unit to an independent motorcycle battery to keep the devices warm and their internal batteries charged. Both units recorded data for 23 hours straight until a guided group retrieved them the next day.聽
Results from the survey could be available by mid-August.聽