Mapping Mount Everest

Alex Tait, geographer at the National Geographic Society, recounts his experiences on an expedition to the world's tallest mountain.

Tents at Mount Everest Base Camp

Researchers installing a surveying station near Everest Base Camp.
Researchers installing a surveying station near Everest Base Camp.

Cover: Aerial view of NGS tents at Base Camp. Photo by Eric Daft. Above, Alex Tait and Tenzing Sherpa install a survey base station on a bench above Everest Base Camp. Photo by Brittany Mumma.

I’m Alex Tait, The Geographer at National Geographic.

This spring, I had the amazing opportunity to lead the mapping team on the 2019 National Geographic and Rolex Perpetual Planet Extreme Expedition to Mount Everest, undertaken in partnership with Tribhuvan University. Our goals were to scan and perform detailed photogrammetry of the entire Khumbu glacier from the South Col all the way down to the toe of the glacier and to scan all of Everest Base Camp—at the highest resolution ever collected at Mount Everest.

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Mount Everest in 3D. Imagery provided by Digital Globe

A locator map showing Mt. Everest's position in northern Nepal.

Everest, the world's highest mountain at 8,849 meters (29,032 feet), straddles the China-Nepal border amidst a rugged wilderness of snow, ice, and rock. On its southeastern shoulder rests Khumbu Glacier, one of thousands sprawled across the Himalaya. Meltwater from these glacial terrains supplies great river systems that in turn provide essential water to huge populations in India, China, Pakistan, and Bangladesh.

It's this larger picture that makes our mapping work so important. Understanding the dynamics of Himalayan glaciers will help us anticipate how climate change will affect the water supplies upon which millions of people depend.

Extending a tradition

Everest map, 1988

A black-and-white portrait of Bradford Washburn next to a plane, holding a camera and wearing a full flight suit

Courtesy Bradford Washburn (published in National Geographic in 1938).

In many ways we were following in the footsteps of Bradford Washburn, who worked on several projects with National Geographic to map high mountain areas. His technical and cartographic work in creating a topographic map of Mount Everest, published by the National Geographic Society in 1988, set the standard of excellence for mapping the mountain. With our work this year, we wanted to honor that tradition and push the boundaries of what is possible in mapping at extreme elevations.

Right: National Geographic's 1988 map of Mount Everest. Map by Bradford Washburn.

Everest Expedition, 2019

My team was able to collect imagery and 3D data at a resolution (1-5cm) that shows the most intricate details of the Khumbu glacier and Everest Base Camp. The maps we produce from this data will help glaciologists and other scientists better understand the dynamics of the ice and snow on the mountain and how this area is changing due to a warming climate.

Researcher Alex Tait examines a Lidar station.

Alex Tait works with terrestrial Lidar mapping equipment to complete the most detailed Lidar and photogrammetric imaging of the Everest Base Camp area. Photo by Mark Fisher.

Map imagery source: Digital Globe, Airbus; Image processing: URSA Space Systems, VRICON.

The science

The ground-based mapping and scanning work of the expedition focused on collecting data and imagery that would be processed into an extremely high-resolution, 3D map of Everest Base Camp, the most detailed ever produced. Our tools are laid out here in the mapping and imagery tent at Base Camp.

A panoramic view of the "science tent," with mapping equipment labeled.

Equipment in the mapping science tent. Photo by Chris Millbern.

Collecting Lidar data

We used a tripod-mounted Lidar (light detecting and ranging) system to collect data that provides the basic structure of the model. This advanced Lidar machine sends a beam of light—at two million pulses per second—out to a radius of about 150 meters. The light pulses bounce back as they encounter objects, and the device records the points in 3D space.

Alex Tait stays out of the scan while collecting Lidar data with the help of a Base Camp dog. Photo by Sandra Elvin.

Alex Tait collects Lidar data

The millions of points together create a 3D point cloud of all the surfaces hit. The resulting data set provides detail of the landscape at sub-centimeter resolution, and is then paired with corresponding photos to color the points and recreate the terrain in full color.

This clip may look like conventional video footage; in fact, it's a 3D model made from exquisitely detailed lidar data combined with imagery.

A photo of an iPad screen displaying Lidar collection locations.

An iPad screen displays a Lidar point cloud of collection locations and tent outlines. Photo by Alex Tait.

Right: A 3D model made from exquisitely detailed Lidar data combined with imagery. Video by Corey Jaskolski.

Flying drones

We used drones extensively on the expedition. High-resolution cameras on the drones captured straight-down views and oblique perspectives that we used for detailed photogrammetry. The drone images enhanced and supplemented the 3D data from the Lidar—including some areas that the Lidar may have missed—and allowed us to add color and texture at the highest possible resolution.

Chris Millbern, a member of the expedition mapping team, works with terrestrial Lidar mapping equipment to complete the most detailed photogrammetric imaging of the Everest Base Camp area. Photo by Mark Fisher.  

A National Geographic researcher operates a drone near Everest Base Camp.

Here's a sample video that we recorded in May 2019 of the tent city that is Everest Base Camp.

A drone flyover of Base Camp. Video by Chris Millbern.

We also made many photographs at ground level using 42-megapixel hand-held cameras. These images provided additional detail and texture to the 3D models and maps and contributed to the composite digital model.

In the approximately one-square-kilometer area of Base Camp we collected 364 Lidar stations, over 8,500 drone photos, and over 24,000 ground-level photos. The result: combined imagery and 3D data that vastly exceeds the accuracy and detail of previous mountain surveys.

A visual comparison of the best-available satellite imagery and the high-resolution 3D data collected on the expedition.

New data from the Everest expedition compared to the best-available satellite imagery. Image by Corey Jaskolski.


A challenging environment

Everest Base Camp, the day after a storm. The tents are dusted with snow.

Heather Clifford walks across Everest Base Camp the evening after a snowstorm. Photo by Brittany Mumma.

We lived at 5,300 meters for six weeks. The constant fatigue from having only half of the oxygen at sea level is like nothing I’ve previously experienced in the field. Just walking up the ten-meter hill to our tents would leave me breathing hard.

A portrait of Alex Tait as he rests indoors while recuperating from an altitude-induced respiratory infection.

Alex Tait recuperates at a lower altitude. Photo by Amrit Ale.

And then there were the illnesses that hit most of our team. I was one of the first to go down with an upper respiratory infection that I got on the ten-day trek up to Base Camp. It left me sleeping most of the day after I arrived. After only two days at Base Camp, I had to retreat to lower elevations to recover.

Nights at Base Camp were cold, and although I was exhausted I couldn’t sleep through the night. There were the regular breaks due to drinking copious amounts of tea and water to stay hydrated, but there were also loud noises coming from high above.

Avalanches boomed down almost every night from the steep rock and ice cliffs of Pumori and Nuptse—some small and some not so small. They sounded like thunder, making a loud crack when a serac (ice ridge) broke off from an ice cliff, and then rolling booms as the ice tumbled down and broke apart until a cloud of tiny ice bits and snow hit the lower slopes.

Of course we had these during the day as well. I filmed one of the larger ones from Nuptse, with a snow cloud ultimately reaching the NGS section of Base Camp. At night, when you can’t tell how large the volume of ice is or whether our camp will be within range of the resulting avalanche, the noises were unnerving.

An avalanche breaks free from the flanks of Nuptse near Mount Everest, as seen from Everest Base Camp. Video by Alex Tait.


The yellow tents of the National Geographic expedition cover a broad swathe of Everest Base Camp.

An aerial view of NGS tents at Everest Base Camp. Photo by Alex Tait.

Living and Working at Base Camp

Researchers relax outside of a tent at Everest Base Camp.

Expedition team members meet at Everest Base Camp. Photo by Alex Tait.

After recovering from my bronchitis and returning to Base Camp, I began working in earnest with my mapping partner Chris Millbern. The first step was to take a goodwill tour through the sprawling camp. We would soon be traipsing through each expedition’s camp with our lidar on a tripod and flying our buzzing drone overhead.

Once we explained the work we were doing to map and better understand the high mountain environment, people were universally supportive. Pete Athans, our expedition climbing leader, who has the nickname “Mr. Everest” due to his seven summits, came with us. He had friends in all the big camps, which eased our way considerably.

As I worked my way through Base Camp, I met people from many different teams. Many of the Sherpa climbing leaders introduced themselves and offered me tea. As I chatted with them I was able to learn how the Base Camp area had changed over the past 30 years. Not only are there far more expeditions and people today, but large flat areas where it had been easy to set up camps have disappeared, replaced by a much more rugged, rubble-covered ice terrain with many “penitentes,” as the spiky ice hills and cliffs on a glacier are called.

An illustration demonstrating how the narrow profile of the glaciers impedes efforts to measure glacial retreat from the air.

Ice loss in mountain glaciers lowers their surface more than it reduces their width and length.

The Sherpas also talked about how much lower the surface of the glacier was, and how much it had receded. The lowering is far more pronounced than horizontal retreat in steep-sided alpine valleys. These anecdotes reinforced the record of glacial change recorded in satellite imagery. The data we collected during our expedition allows us to more precisely determine how the glaciers have changed, and established a very accurate baseline of the glacier’s extent in 2019. Additionally, the data we have collected will enable better predictions of how the glacier will change in the future under different global warming scenarios.


Science by chopper

An interior, mid-flight view of the helicopter used to control and monitor the Lidar stations.

Inside the Airbus 3BE helicopter used for Lidar and photo mapping of the entire Khumbu Glacier. Photo by Ron Chapple.

Utilizing the latest Lidar equipment, we were able to collect 2-5cm resolution 3D data for the entire Khumbu Glacier and its adjacent mountain walls and moraines (the piles of rock and dirt that are left by a glacier when it recedes), an area of over 65 square kilometers. The helicopter-based equipment included Lidar and megapixel cameras that collected visible and infrared imagery.

Point clouds from the Lidar, and digital terrain models from the photographic imagery, combine to produce the highest-resolution ever model of a complete Himalayan glacier. This model includes the lateral and terminal moraines as well as the mountain walls adjacent to the glacier.

Color photography will complete the 3D model of the world’s highest glacier, providing scientists with a phenomenal dataset with which to study glacial structures and dynamics. Because we collected data over an eight-day period, we have captured daily and weekly changes in the snow and ice—details which scientists can use to predict changes to the glaciers in this critical and frequently-visited high-mountain area.

A map showing the overlapping, zig-zagging path flown by the helicopter to map the Khumbu Glacier from above.

The path flown by the Airbus 3BE helicopter to map the entire Khumbu Glacier using Lidar and photo data. Photo by Kenny Broad.

Aerial footage from the helicopter with Lidar device attached. Video by Ron Chapple.

The 3D model of the Khumbu Glacier provides important data for meteorologists as well. Our meteorologic team, who set up the the  world's highest weather station , can use data on daily changes in snow and ice to test models of how temperature and environmental conditions affect melt rates and other changes to the snow and ice.


The big picture

The high-mountain glaciers of the Hindu Kush-Himalaya feed many of the largest and most important river systems in Asia. Although precipitation throughout each river basin is important, the water stored as high alpine ice and snow in these "water towers" is a critical component to the  water needs downstream —for human household, agricultural, and industrial use, and the needs of the natural ecosystem.

The Himalayan drainage

The Ganges and Brahmaputra in South Asia and the Yangtze and Yellow Rivers in China all originate in the high mountains and receive meltwater from the glaciers and snow pack.

Maps by Cooper Thomas, Esri's StoryMaps team.

A map of Asia, with the ten river systems fed by the Hindu Kush-Himalaya highlighted and labeled.

Downstream populations

The ten river systems of the Hindu Kush-Himalaya provide water to 1.9 billion people—a full quarter of the planet's population.

A map of population density in Asia, with the Hindu Kush-Himalayan river systems highlighted.

Urban centers

Growing cities in Pakistan, India, Bangladesh, and China are dependent on Himalayan waters. Among them: Lahore, Delhi, Dhaka, and Chongqing.

As climate change and other human influences affect the snow and ice, human and natural communities in downstream areas will need to adapt.

A proportional symbol population map of major cities in Asia, with the Hindu Kush-Himalaya river systems highlighted.

Understanding a dynamic system

The Perpetual Planet Extreme Expedition to Everest is contributing state-of-the-art data and trailblazing scientific research that will enhance our knowledge of the changes to the glaciers, snow, and ice of the highest mountains in the world—the water towers serving more than a billion people.

Information from this expedition will contribute to better understanding of past and current environmental conditions, and help to better predict how the mountain environments and downstream areas will change in years to come. Better predictions can enable better adaptations for the human and natural communities that rely on the water from the high mountains.

A long-exposure image of the Everest summit in twilight.

Headlamps illuminate the path that climbers take as they move up the Khumbu Icefall above Everest Base Camp in the early morning hours. Photo by Eric Daft.

Cover: Aerial view of NGS tents at Base Camp. Photo by Eric Daft. Above, Alex Tait and Tenzing Sherpa install a survey base station on a bench above Everest Base Camp. Photo by Brittany Mumma.

Equipment in the mapping science tent. Photo by Chris Millbern.

New data from the Everest expedition compared to the best-available satellite imagery. Image by Corey Jaskolski.

Heather Clifford walks across Everest Base Camp the evening after a snowstorm. Photo by Brittany Mumma.

Alex Tait recuperates at a lower altitude. Photo by Amrit Ale.

An aerial view of NGS tents at Everest Base Camp. Photo by Alex Tait.

Expedition team members meet at Everest Base Camp. Photo by Alex Tait.

Ice loss in mountain glaciers lowers their surface more than it reduces their width and length.

Inside the Airbus 3BE helicopter used for Lidar and photo mapping of the entire Khumbu Glacier. Photo by Ron Chapple.

Headlamps illuminate the path that climbers take as they move up the Khumbu Icefall above Everest Base Camp in the early morning hours. Photo by Eric Daft.

Courtesy Bradford Washburn (published in National Geographic in 1938).

Right: National Geographic's 1988 map of Mount Everest. Map by Bradford Washburn.

Alex Tait works with terrestrial Lidar mapping equipment to complete the most detailed Lidar and photogrammetric imaging of the Everest Base Camp area. Photo by Mark Fisher.

Map imagery source: Digital Globe, Airbus; Image processing: URSA Space Systems, VRICON.

Alex Tait stays out of the scan while collecting Lidar data with the help of a Base Camp dog. Photo by Sandra Elvin.

An iPad screen displays a Lidar point cloud of collection locations and tent outlines. Photo by Alex Tait.

Right: A 3D model made from exquisitely detailed Lidar data combined with imagery. Video by Corey Jaskolski.

Chris Millbern, a member of the expedition mapping team, works with terrestrial Lidar mapping equipment to complete the most detailed photogrammetric imaging of the Everest Base Camp area. Photo by Mark Fisher.  

A drone flyover of Base Camp. Video by Chris Millbern.

An avalanche breaks free from the flanks of Nuptse near Mount Everest, as seen from Everest Base Camp. Video by Alex Tait.

The path flown by the Airbus 3BE helicopter to map the entire Khumbu Glacier using Lidar and photo data. Photo by Kenny Broad.

Aerial footage from the helicopter with Lidar device attached. Video by Ron Chapple.

Maps by Cooper Thomas, Esri's StoryMaps team.