Case Studies of Landsat Imagery Use
Open-access Satellite Data
Changes in land cover affect the global climate by absorbing and reflecting solar radiation, and by altering fluxes of heat, water vapor, carbon dioxide, and other trace gases. Detailed assessments—regional, global, daily, and seasonal—of land use and land cover are needed to monitor biodiversity loss and ecosystem dynamics. Satellite imagery is the best source of such data, especially over large areas. In many cases, satellite data are restricted or charged for. Not true for U.S. Geological Survey (USGS) satellite imagery.
A new era of open-access satellite data began in 2008 when the USGS released its Landsat archive, the world’s largest collection of Earth imagery, to the public free of charge. Monitoring land cover change in near-real time is now a reality. According to an article by Michael A. Wulder and Nicholas C. Coops in Nature magazine, “Freely available satellite imagery will improve science and environmental-monitoring products.” Read the full story here.
Observing Earth Today and Tomorrow: A National Plan
Humans have been observing Earth for a very long time simply because the conditions of the Earth are basic to our survival and our prosperity. Even the most ancient written records are filled with accounts of great floods, famines, and earthquakes. When to plant and when to harvest, how to use precious water resources most effectively, and ways to avoid natural disasters are all age-old challenges that have encouraged Earth observation from the beginning of civilization. Read the full story here.
Landsat’s Lunar Scans
Even though Landsat 8 is an Earth-imaging satellite, it was designed to turn away from Earth once a month and scan the moon. Landsat’s sensors need to detect light consistently over time. The best way to measure Landsat’s performance is to compare it to a stable source of light. The calibration team at the NASA Goddard Space Flight Center and the USGS EROS Center use the most stable light source they can—moonlight. With these lunar scans, the engineers can adjust the calculations that turn Landsat’s data into accurate land cover information. Read the full story here and see a video created by NASA Goddard that demonstrates in detail how Landsat 8 conducts its lunar scan.
National Land Cover Database 2011 on YouTube
Learn more about the National Land Cover Database 2011 (NLCD 2011) from Dr. Collin Homer, USGS Earth Resources Observation and Science (EROS) Center. In a YouTube video presentation, Homer describes the status, future plans, and applications examples of NLCD 2011. The presentation clearly describes NLCD’s flagship products: land cover, canopy, and imperviousness. Homer emphasizes that NLCD is valuable because it is consistent and relevant. Its national coverage also supports many different applications: fire, urban development, insect damage, mining, and more. Find out what Homer means by "30 billion pixels served" at https://www.youtube.com/watch?v=GekyUrZoYys.
New Teaching Resource for Remote Sensing
The Tracking Change Over Time lesson is intended for students in grades 5–8. It enhances students’ learning of geography, earth science, and problem solving by seeing landscape changes from space. The lesson plan includes an introduction to satellite images, an introduction to remote sensing, instructions on how to use the free software MultiSpec, and modules that go deeper into specific areas of remote sensing application.
In the latest module, "River Flooding", students discover how a flood in June 2008 affected southern Indiana and Illinois. The module takes a problem-based approach to show students how satellite images can be used to analyze the changes that a flood causes. The images used in the lesson, along with supplementary materials, are also available at http://eros.usgs.gov/educational-activities.
Landsat 7 Marks 15 Years of Observing Earth
For the past 15 years Landsat 7, launched on April 15, 1999, has continued the legacy of Earth observations started by the Landsat program in 1972. Landsat 7’s remarkable longevity has been vital to the majority of Landsat data users who require frequent imaging of specific areas for land and resource management. Today, Landsat 7, working in tandem with Landsat 8, continues to provide a continuous, unbiased record of change across the earth land surface.
For more information about Landsat 7’s first 15 years, please see the USGS Press Release.
Taking Landsat to the Extreme: The Coldest Place on Earth
What is the coldest place on Earth? It’s a high ridge in Antarctica on the East Antarctic Plateau, as seen on the Landsat Image Mosaic Of Antarctica (LIMA) image on the left . Temperatures in several hollows of the plateau can dip below minus 133.6 degrees Fahrenheit (minus 92 degrees Celsius) on a clear winter night.
With remote sensing satellites, including Landsat 8, researchers have recorded new measurements of the Earth's coldest temperatures. The satellite imagery not only allows scientists to take the temperature of these inhospitable locations, but enables them to figure out what sort of weather brings on the record-breaking cold.
The quest to find out just how cold it can get on Earth -- and why -- started when NASA researchers were studying large snow dunes, sculpted and polished by the wind, on the East Antarctic Plateau. When the scientists looked closer, they noticed cracks in the snow surface between the dunes, possibly created when wintertime temperatures got so low the top snow layer shrunk. This led scientists to wonder what the temperature range was, and prompted them to hunt for the coldest places using data from satellite sensors: MODIS (Moderate Resolution Imaging Spectroradiometer), AVHRR (Advanced Very High Resolution Radiometer), and Landsat 8 - TRS (Thermal Infrared Sensor).
More information about the coldest place on Earth can be found at http://science.nasa.gov/science-news/science-at-nasa/2013/09dec_coldspot
USGS & NASA to host a sustainable land imaging users forum
The U.S. Geological Survey (USGS) and NASA will host an event on December 4 to discuss how to assess user needs for global, continuous Landsat-quality satellite imagery in support of NASA’s Sustainable Land Imaging Program.
User requirements are a critical resource in designing and implementing future satellites. The USGS has been developing a structured methodology for acquiring, cataloging, maintaining and evaluating user requirements for Earth observations through its Land Remote Sensing Program, which manages the USGS contributions to the joint efforts of USGS and NASA for the Landsat program.
The Users Forum will feature the methodologies and approaches the USGS is using to acquire and evaluate user requirements, a presentation of methods and preliminary findings, as well as opportunities for feedback with regard to the approach and requirements gathered to date.
Changes in World’s Forests Portrayed in High Definition
The importance of forest ecosystem services is recognized around the world; however, previous methods of tracking global forest change were based on data that did not have enough detail to accurately measure change. A new study published in Science magazine is changing that.
Matthew C. Hansen of the University of Maryland, assisted by co-author Thomas R. Loveland, chief scientist at the USGS Earth Resources Observation and Science (EROS) Center in Sioux Falls, S. D., led this unparalleled survey of global forests. The team of scientists interpreted over 650,000 Landsat 7 scenes to create global maps of forest change. The maps are the most detailed and complete assessment of global forest dynamics available. Global tree cover extent, loss, and gain were mapped at 30-m resolution, higher detail than ever before. Globally during this period, 2.3 million square kilometers of forest were lost, and 0.8 million square kilometers were gained.
"Tracking changes in the world's forests is critical because forests have direct impacts on local and national economies, on climate and local weather, and on wildlife and clean water," said Anne Castle, Assistant Secretary of the Interior for Water and Science. "This fresh view of recent changes in the world’s forests is thorough, objective, visually compelling, and vitally important."
"Ever since the USGS made Landsat data free to anyone in 2008, Landsat imagery has served as a reliable common record, a shared vocabulary of trusted data about Earth conditions," Castle continued.
Tom Loveland added, "This multi-organization project was only feasible with the existence of free Landsat data. The invaluable Landsat archive supplies high-quality, long-term, consistent global data at a scale appropriate for tracking forest gains and losses."
The 41-year Landsat record of changes on the Earth's surface is continuously updated in the Landsat archive maintained by the USGS EROS Center.
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