Why NASA wants you to point your smartphone at the trees

NASA would like you to take a picture of a tree, please. The space agency's ICESat-2 satellite estimates tree height from space and NASA has created a new tool for citizen scientists that can help verify these measurements from the ground up. All you need is a smartphone, an app, an optional tape measure and a tree.

Launched in September 2018, the ICESat-2 satellite is equipped with an instrument called ATLAS, which sends 60,000 light pulses to the Earth's surface every second as it turns around the planet. "It's basically a laser in space," says Tom Neumann, scientific lead for the ICESat-2 project at NASA's Goddard Space Flight Center. By measuring the position of the satellite, its angle and the time it takes for these laser beams to bounce off the surface, scientists can measure the altitude of sea ice, ground ice, ocean, inland waters and trees. Knowing the height of trees can help researchers assess the health of the world's forests and the amount of carbon dioxide they can absorb.

But Neumann says that a big open question is how good are these measurements from the space. This is where citizen science comes in – to help verify them. Some are more difficult than others. "You can not really ask a group of schoolchildren in Pennsylvania to go to Antarctica to measure the height of the pack ice for calibration," he says. But you can Ask them to take out their smartphone, which is exactly what NASA does with its GLOBE Observer app. "You have all sorts of great grounds and features in your garden that allow you to do those things that could be helpful," says Neumann.

After downloading the NASA GLOBE Observer application, you can choose from various tools to record cloud observations, mosquito habitats and the landscape around you. There is also a new tool for measuring trees, called GLOBE trees. When you open it for the first time, a complete tutorial tells you how to calibrate the application and take steps that allow it to triangulate the height of the trees. The tutorial contains useful tips for tasks such as "Select a Tree." Apparently, bent and broken trees are not measured.

Once you have selected your unbroken tree and have located a location about 25 to 25 meters away, you hold the phone right in front of your face and tilt it to measure the base then the top of the tree. 39; shaft. Then you take a picture, count your steps towards the tree, record your position at the base and the application spits at the height of the tree. When I tried it, my tree was backlit, surrounded by other trees and I discovered that, thanks to the camera, it was difficult to distinguish the top from the one in relation to the top of the tree behind. These conditions are not ideal for measuring trees, according to the tutorial. Nevertheless, the height of 20 feet that the application appeared seems rather close to the right.

Since the official launch in late March, GLOBE Trees has received about 700 measurements from over 20 different countries, according to Brian Campbell, Earth Science Awareness Specialist for NASA, responsible for Trees Science . And researchers would like to have more. The measurements are useful data for the ICESat-2 team, says Neumann. So when it comes to using the app, he says, "The more we are crazy, the more we laugh."