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PE and RS PUBLIC April 2011 : Page305

Change Matters By Kass green Introduction Change happens. All the time. Floods, wildfires, population growth, pest outbreaks, earthquakes, droughts and wars all inflict change upon our landscape. The ramifications of these changes become more significant over time as the world’s population continues to grow, and the resiliency of our environments becomes increasingly taxed. To plan for the future and to manage our resources wisely, we need to understand what has happened in the past -we need to monitor change. Comparing remotely sensed images over time has long been a riveting and effective method for monitoring change caused by population growth (Jensen, 1981), land use transformation (NOAA-CSC, 2011) forest harvesting (Tucker and Townshend, 2000; Goward et al. , 2008), pest outbreaks (USDA, 2011), drought (USDA-FAS, 2001) floods (Steinbruch et al ., 2002), and wildfires (USDA-FS, 2011), among others. Recently three major transformations in policy and technol-ogy culminated to bring rapid remote sensing change detection functionality to a broad spectrum of internet users. 1. In 2008, the Department of the Interior announced its plan to make the U.S. government’s Landsat satellite imagery free and accessible via the internet. Subsequently, the U.S. Geological Survey (USGS) and National Aeronautics and Space Administration (NASA) partnered to post the Global Land Survey (GLS) (http://landsat.usgs. gov/science_GLS2005.php) epochs of Landsat imagery, comprised of one image per each epoch worldwide from the 1970s, 1990s, 2000, and 2005. Images included in each GLS epoch are chosen for peak growing season and minimal cloud cover. 2. In 2010, Esri ( released ArcGIS Server 10 with the enhanced Image extension that has revolutionized how imagery is served, simplifying image management and increasing image access speed. Simultaneously Esri committed to serving the worldwide GLS Landsat data over the Web to all users for free. 3. In 2011, working with partners, Esri developed a Web tool, ChangeMatters 1 , which allows users to navigate around the globe and quickly view the GLS Landsat imagery both multi-spectrally (in different Landsat band combinations) and multi-temporally (across epochs), and to conduct simple change detection analysis. ChangeMatters provides increased access of Landsat imag-ery to both scientific and non-scientific users. This article introduces ChangeMatters by reviewing its background, functionality, and educational user interface. Landsats 5 and 7 additionally collect imagery in the thermal, and mid, and far infrared portions of the spectrum. Because human sight is limited to the optical portions of the spectrum, collection of data in the non-optical portions allows users “to see” phenomena that humans cannot perceive with their eyes. Figure 1 compares the different band combinations of Landsat imagery which highlight different types of land cover. Figure 1. Landsat GLS 2000 imagery displayed in natural color, (a) veg-etation analysis (b), and infrared (c) ImageMaps in Esri’s ChangeMatters web browser. Continuity of Observations Background First launched in 1972, the imagery from the six successful Landsat missions provides continuity in Earth observations over the last four decades. All early Landsat missions captured imagery in the non visible infrared and the visible optical green and red portions of the electromagnetic spectrum. Current 1 All Landsat missions have been configured to ensure con-tinuity of Earth observation. Therefore, each new mission was designed so that scientific comparisons can be made of imagery collected from any mission. Table 1 shows how the spectral ranges of each band have remained relatively unchanged across all missions. ChangeMatters allows Internet users to view and compare Landsat imagery in different band combinations and from epoch to epoch. Policy Changes ChangeMatters was developed by Esri with partners Kass Green & Associates, Tukman Geospatial, and DTSagile. Photogrammetric engineering & remote SenSing From 1972 to 1982 imagery collected by the Landsat missions was available to the public at low cost. However in 1979, Presi-dent Carter signed Presidential Directive 54 which authorized continued on page 306 April 2011 305

Change Matters

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