Trees FAQs

Find answers to frequently asked questions about the Trees tool:

Why measure tree height?

Tracking how trees are changing over time can help us estimate the number of trees that make up an area. Tree height is the most widely used indicator of an ecosystem’s ability to grow trees. Observing tree height allows NASA scientists to understand the gain or loss of biomass which can inform calculations of the carbon that trees and forests either take in from or release into the atmosphere.


What do trees have to do with Earth’s carbon budget?

Trees cool and moisten our air and fill it with oxygen and can help balance our carbon budget. Forests are considered one of the world’s largest banks for all of the carbon emitted into the atmosphere through natural processes and human activities. They cover about 30 percent of Earth’s land surface, while accounting for 50 percent of plant productivity. As much as 45 percent of the carbon stored on land is tied up in forests. Trees undergo photosynthesis. Photosynthesis is a complicated process where carbon dioxide and water are converted to glucose (a simple sugar) and oxygen.


Why are we also measuring tree circumference?

Tree circumference measurements can be used to estimate the volume, biomass, and carbon storage of trees.


What if I can't reach all the way around the tree, how do I measure circumference?

If you don't have another person to help you, try making a small mark with your fingernail as far as you can reach, and measure the circumference in two stages.


What is ICESat-2?

In addition to measuring the height of Earth’s ice sheet, sea ice, and glaciers, the NASA Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) will also survey heights of the world’s forests, lakes, urban areas, cloud cover and more, adding a third dimension of Earth from space.


What can I use to compare the tree height data I collected to the data from ICESat-2?

ICESat-2 (and ICESat) elevation data can now be visualized on the National Snow and Ice Data Center’s (NSIDC) Open Altimetry Tool. Data for the new ICESat-2 mission were released to the public on May 28, 2019. OpenAltimetry provides access to all ICESat-2 data for which there is a complete set of data products, including canopy (tree) height. If the ICESat-2 satellite collected data over your observed tree location, you can view ICESat-2 elevation data corresponding to your tree’s latitude and longitude. This ICESat-2 dataset will continue to expand as ICESat-2 collects new data in the years to come.


What is the purpose of comparing my GLOBE Tree Height data with the data from NASA missions?

GLOBE Observer: Trees height data can serve as a source of data comparison for the ICESat-2 satellite. ICESat-2 utilizes an onboard laser altimeter system to measure the height of our planet, one photon at a time. The technology of ICESat-2 can measure the height of trees all around our planet. GLOBE observers can share their data with NASA scientists and can be part of vital missions that make NASA science even better.


What is GEDI?

The GLOBAL Ecosystem Dynamics Investigation (GEDI) measures precise height measurements of surface water, ice, vegetation, and the land surface can improve estimates of flood risk from storms, fresh-water supplies, forest resources, and can help identify priorities for biodiversity conservation.


How can scientists and researchers use my tree height and tree circumference observations?

Tracking how trees are changing over time can help estimate the amount of trees that make up an area’s biomass – the total mass of organisms in a given area or volume

Taking these observations can serve as a step to help scientists and researchers understand how trees help us balance Earth’s carbon budget.


How many tree heights should I measure?

Record the height of trees in as many places as you would like. Also, you can measure the same tree many times, in order to see potential changes to tree heights over time.


What defines the top of a tree and the base of a tree?

Top of a tree: also known as the canopy or crown of a tree, it is the uppermost part of the tree.

Base of a tree: the lowest part of the tree trunk that is still above ground


Why do I need to report on surface conditions?

Surface conditions are an important part of trees observations. Knowing the local environmental conditions will allow for a much more robust dataset that can be used in defining the local ecosystem. By reporting surface conditions, you are also providing additional data to assist during analysis and satellite validation.


How do I change from metric to English units or vice versa, or change my height?

While in the Trees tool, tap on the question mark at the lower right, and select "Introduction." Walk through the screens and change any settings you wish to modify.


I'm getting an error message "Invalid Angles:  Please step further away from the tree to better measure the top and bottom," but it doesn't go away when I walk further away from the tree. What should I do?

If following the directions and moving further away doesn't clear the error message, your device may not have the gyroscope needed to measure the angles and calculate tree height using the app. You can check your device specifications to be sure. The other tools in the app will not be affected.