News - GLOBE Observer
Announcing New Land Cover Satellite Comparisons
A group of elementary-aged students gather outside of Oldham County Public Library in La Grange, Kentucky, United States to look at clouds in the sky. “If anyone asks what you are doing, tell them, ‘I am a citizen scientist and I am helping NASA,’” Children’s Programming Librarian, Cheri Grinnell, tells the kids. Grinnell supports an afterschool program called Leopard Spot where she engages K-5 students in collecting environmental data with GLOBE.
“One little boy really got excited about that, and I heard him tell his mom he was working for NASA as they were leaving,” says Grinnell. That idea is reinforced when the program receives an email from NASA with satellite data that aligns with the cloud data they submitted. “I forwarded the NASA satellite response to the after-school coordinator, and she read it to them. That really excited them because it was evidence this is the real deal.”
This experience is one we hear often: GLOBE volunteers of all ages love getting an email from NASA that compares satellite data with their cloud observations. “Feedback from NASA is huge. It’s the hook,” says Tina Rogerson, the programmer at NASA Langley Research Center who manages the satellite comparison emails. “It ties the NASA science into what they saw when they did the observation.”
Since 2017, GLOBE volunteers have received satellite comparison images that match their GLOBE Clouds observations. In this case, the observer reported mostly clear skies with isolated cumulus and altocumulus clouds, an assessment supported by the satellite image from the space place and time. The blue circle on the GOES-18 satellite image marks the volunteer’s location.
Now, volunteers will have more opportunities to receive a satellite comparison email from NASA. We are excited to announce that we will now be sending emails comparing GLOBE Observer Land Cover observations with satellite data. The new satellite comparison for land cover builds on the system used to create cloud comparisons at NASA Langley Research Center.
These new collocated land cover observations are expected to raise greater awareness on how NASA and their interagency partners observe our changing home planet from space to inform societal needs. It will help every GLOBE volunteer see how their observations of the land fit in the larger space-based view and how they are participating in the process of science. Based on the response from cloud satellite emails, seeing that perspective in the satellite comparison email is motivating. We hope it encourages volunteers to continue collecting Earth system observations for GLOBE’s long-term environmental record.
Landsat and GLOBE
An artist's conceptualization of the Landsat 9 satellite. Image courtesy NASA's Scientific Visualization Studio.
Providing Landsat images to GLOBE volunteers is not new. In fact, Landsat was part of GLOBE’s origin, says Dr. Dixon Butler, one of GLOBE’s earliest chief scientists. Prior to the founding of GLOBE, Dr. Barry Rock, a forest ecologist from University of New Hampshire (UNH), engaged students in using Landsat data to look at land cover change in New England. “He shared a video of middle school girls looking at a Landsat image, and one said, ‘let’s look at the false color infrared,’” recalls Butler. “He showed that kids were capable of complex data collection. Danielle Miller Wagner (who later became GLOBE’s International Policy Analyst) at the White House saw the video, and invited Barry to Washington, D.C. for a meeting. GLOBE was created in that meeting.”
Rock became GLOBE’s first chief scientist, and he encouraged his UNH colleague, Dr. Russell Congalton, to propose a protocol based on land cover and Landsat for GLOBE measurements. Congalton developed the original GLOBE land cover classification and mapping protocols. (Note: GLOBE Observer Land Cover collects land cover photographs and optional classification data using a different, simplified method.)
Teachers learn about land cover classification and Landsat in an early GLOBE workshop. Photo courtesy Dr. Russel Congalton.
To encourage data collection at the onset of the program, GLOBE mailed a 15 kilometer by 15 kilometer Landsat scene on a floppy disk to schools that participated in collecting land cover data. “The study site was 15 by 15 kilometers because that was the amount of data that fit on a floppy disk,” says Jennifer Bourgeault, now the GLOBE United States Country Coordinator.
“We felt it was very important to make the connection between measurements taken in the field and what can be seen in the Landsat data,” says Congalton. “If you give them an image to compare to what they saw on the ground, we thought that teachers and students would get excited about collecting more data.” The idea, he says, was to encourage schools to map as much of their Landsat scene as possible. “The students got very excited about seeing the image,” says Congalton.
GLOBE students measure land cover as part of a GLOBE Annual Meeting.
“The real value came in exploring the images to identify changes,” says Bourgeault . She was a former educator who joined Congalton’s team to support implementing GLOBE Land Cover in GLOBE’s early days. She recalls working with a group of students who saw a wetland in their imagery where a large store had recently been built. “They heard the debate in the community about putting the store in that location, and they asked, why did we remove the wetland for the store,” says Bourgeault. “The value is perspective. A satellite image connects your place to a larger area. You are part of a bigger system.”
Image distribution stopped when Landsat data became easily accessible online at no cost. Schools no longer needed GLOBE to send them the Landsat scenes. But given everything else teachers had to manage, they struggled producing the images themselves, says Congalton. He observed that the integration of GLOBE and Landsat slowed to a few deeply invested teachers. However, he thinks that with improved and easier-to-use technology to explore satellite data, the time is right to resume connecting GLOBE Land Cover to Landsat data. “We need a do over. The age of remote sensing is here now.”
A Fresh Start with GLOBE Land Cover and Satellite Data
Congalton—and GLOBE—may be getting a do-over with respect to the new satellite collocation tables produced by NASA Langley as part of GLOBE Observer Land Cover. GLOBE has evolved from being a school-based science program to a citizen science program that welcomes participation from people of all ages. So, this time, instead of sending a single scene to a participating school, anyone who submits GLOBE land cover data will get an image every time they take an observation. And rather than sending data by hand through the mail, the matches are made automatically in a system managed at NASA Langley Research Center.
Creating the automated system was a long process started by intern Siddharth Jasti (shown in the photo on the left) in the summer of 2023. Sidd explored an approach for identifying satellite data co-located with GLOBE Observer land cover observations. He explored ways to display a volunteer’s land cover observation and photos and how to pull in and display satellite data taken at the same place and time.
Jasti’s work was fully developed and implemented by his successor, Logan Butler, and Tina Rogerson, who managed integrating land cover satellite match into the existing GLOBE Clouds system at NASA Langley Research Center. The integration proved challenging but rewarding, and after more than a year of work is ready to implement.
Satellite Data Provided in the Land Cover Satellite Comparison Email
When a volunteer receives the email, they will see a link for each observation they have submitted. The link will open a website with a satellite comparison table. Their observation is on top, followed by a satellite-based assessment of the land cover at that location. The last row of the table shows the most recent Landsat and Sentinel 2 satellite images of the observation site.
The land cover classification data in the collocation table is from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument flying on NASA’s Terra satellite. By compiling data across multiple years, scientists can assess the primary type of land cover in a location to create a global land cover map. Each pixel – or area assigned a classification – is 500 meters by 500 meters, a much larger area than GLOBE Observers measure. This means that the satellite-based classification may be different from GLOBE land cover classifications, particularly if the observation site is different from the surrounding land, such as a grassy school yard in a city, or if the land cover has recently changed.
The satellite comparison table will also contain the most recent images of the location from the Landsat 8 or 9 satellites and a Sentinel 2 satellite. Landsat 8 and 9 fly over most locations every eight days, so images in the email may be as much as 8 days older than the GLOBE observation. Sentinel 2, which is a constellation of multiple satellites, flies over every 5 days, meaning those images could be as much as 5 days older. The GLOBE Observer app includes overpass times for the Landsat and Sentinel 2 satellites so you can collect data at the same time to improve the match. Landsat images have a resolution of 30 meters per pixel, so each image pixel is about the same area observed with GLOBE Observer Land Cover. Sentinel 2 has a visible light resolution of 10 meters per pixel. Learn more about the satellites.
Rogerson will pull GLOBE land cover data from the public GLOBE database and generate the comparison tables through her system at NASA Langley Research Center once a week. While users may opt out of receiving these emails (go to "settings" - the gear icon - in the GLOBE Observer app), we hope that most people will be excited to have the opportunity to review their data from the space perspective.
“I’m excited that land cover is finally becoming part of the operational satellite comparison system,” says Rogerson. This means that GLOBE volunteers will routinely receive satellite data for both land cover and clouds. “We are bringing real science right into your world.”
Right, Tina Rogerson takes a GLOBE Clouds observation at NASA Langley Research Center.
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