NASA: Dünya’nın Bilinen En Kapsamlı Topoğrafik Haritası

1.3 milyon görüntüden oluşan veri, Amerikan Havacılık ve Uzay Dairesi (NASA) ile Japonya Ticaret Bakanlığı’nın ortak çalışmasıyla toplandı. Fotoğraflar, Terra uydusuna yerleştirilen; Japonya’ya ait ASTER (İng. Advanced Spaceborne Thermal Emission and Reflection Radiometer) adlı özel veri işlemcisiyle çekildi. Küresel Ölçekte Sayısal Yükselti Haritası ile dünya yüzeyinin yüzde 99′u tarandı. Bu zamana kadar yapılabilen dünya yüzeyinin en kapsamlı haritası yayımlandı. Uzmanlar, verileri, internetten ücretsiz olarak halka sunuyor (bkz. asterweb.jpl.nasa.gov, gdem.aster.ersdac.or.jp).

Dünyayı incelemeye adanmış Terra uydusu deniz yosunlarından volkan patlamalarına kadar çok değişik alanlara ışık tutuyor. ASTER ölçümlerinde bir yerin yüksekliği, her biri diğerinden 30 metre uzaklıkta noktalar baz alınarak görüntüleniyor. ASTER projesinde görevli NASA’dan biliminsanı Woody TURNER, “Bu, bugüne kadar ki küresel ölçekte en kapsamlı, en kalıcı sayısal yükselti verisi” diye konuştu ve ekledi “Bu, Dünya için yapılan küresel ölçekte, en eksiksiz ve tutarlı sayısal yükseklik verileridir. Bu verilerle araştırma yapacaklar, yükseklik ve arazi bilgilerine kolayca ulaşabilecek”.

Bundan önce dünya topoğrafyasına ilişkin en kapsamlı harita, NASA’nın hazırladığı ve dünya yüzeyinin yüzde 80′ine ilişkin bilgileri görüntüleyen haritaydı. Bununla beraber bazı çöllerde ve sarp kara parçalarında doğruluk oranlarının azaldığı biliniyordu. NASA, şimdi bu bilgilerle, ASTER verilerini karşılaştırarak küresel haritayı daha da geliştirmeye çalışıyor.

‘Küresel Ölçekte Sayısal Yükseklik Modeli’ adı verilen çalışma, yaklaşık 1.3 milyon görüntüyü NASA’nın uzay gemisi Terra’ya yerleştirilen Japon yapımı kamerayla çekti. Görüntüler toplam 23 bin karodan (mozaikten) oluşuyor. Yükseltiler farklı renklerle gösterilirken düşük yükseltiler mor, ortalar yeşil ve sarı ve yüksek kısımlar ise turuncu, kırmızı ve beyazla gösterilmiş. Harita, İngiltere’nin ve İrlanda’nın aynı düşük yükseltilerde olduğunu, ayrıca iki ülkenin deniz seviyesine yakın Danimarka, Polonya, Kuzey Rusya’nın, Moritanya, Somali, Brezilya, Arjantin, Florida (Amerika Birleşik Devletleri) ve Avustralya’nın bazı bölgeleriyle benzer yükseltiye sahip olduğu gibi ayrıntıları renklerle gösteriyor.

NASA and Japan’s Ministry of Economy, Trade and Industry (METI) released the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) to the worldwide public on June 29, 2009. The GDEM was created by processing and stereo-correlating the 1.3 million-scene ASTER archive of optical images, covering Earth’s land surface between 83 degrees North and 83 degrees South latitudes. The GDEM is produced with 30-meter (98-feet) postings, and is formatted as 23,000 one-by-one- degree tiles. The GDEM is available for download from NASA’s EOS data archive and Japan’s Ground Data System. In this colorized version, low elevations are purple, medium elevations are greens and yellows, and high elevations are orange, red and white.

With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA’s Terra satellite. The instrument was built by Japan’s Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance. Image Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.

NASA, Japan Release Most Complete Topographic Map of Earth
NASA and Japan released a new digital topographic map of Earth Monday that covers more of our planet than ever before. The map was produced with detailed measurements from NASA’s Terra spacecraft.

The new global digital elevation model of Earth was created from nearly 1.3 million individual stereo-pair images collected by the Japanese Advanced Spaceborne Thermal Emission and Reflection Radiometer, or ASTER, instrument aboard Terra. NASA and Japan’s Ministry of Economy, Trade and Industry, known as METI, developed the data set. It is available online to users everywhere at no cost.

“This is the most complete, consistent global digital elevation data yet made available to the world,” said Woody Turner, ASTER program scientist at NASA Headquarters in Washington. “This unique global set of data will serve users and researchers from a wide array of disciplines that need elevation and terrain information.”

According to Mike Abrams, ASTER science team leader at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., the new topographic information will be of value throughout the Earth sciences and has many practical applications. “ASTER’s accurate topographic data will be used for engineering, energy exploration, conserving natural resources, environmental management, public works design, firefighting, recreation, geology and city planning, to name just a few areas,” Abrams said.

Previously, the most complete topographic set of data publicly available was from NASA’s Shuttle Radar Topography Mission. That mission mapped 80 percent of Earth’s landmass, between 60 degrees north latitude and 57 degrees south. The new ASTER data expands coverage to 99 percent, from 83 degrees north latitude and 83 degrees south. Each elevation measurement point in the new data is 98 feet apart.

The ASTER data fill in many of the voids in the shuttle mission’s data, such as in very steep terrains and in some deserts,” said Michael Kobrick, Shuttle Radar Topography Mission project scientist at the Jet Propulsion Laboratory. “NASA is working to combine the ASTER data with that of the Shuttle Radar Topography Mission and other sources to produce an even better global topographic map.”

NASA and METI are jointly contributing the ASTER topographic data to the Group on Earth Observations, an international partnership headquartered at the World Meteorological Organization in Geneva, Switzerland, for use in its Global Earth Observation System of Systems. This “system of systems” is a collaborative, international effort to share and integrate Earth observation data from many different instruments and systems to help monitor and forecast global environmental changes.

NASA, METI and the U.S. Geological Survey validated the data, with support from the U.S. National Geospatial-Intelligence Agency and other collaborators. The data will be distributed by NASA’s Land Processes Distributed Active Archive Center at the U.S. Geological Survey’s Earth Resources Observation and Science Data Center in Sioux Falls, S.D., and by METI’s Earth Remote Sensing Data Analysis Center in Tokyo.

ASTER is one of five Earth-observing instruments launched on Terra in December 1999. ASTER acquires images from the visible to the thermal infrared wavelength region, with spatial resolutions ranging from about 50 to 300 feet. A joint science team from the U.S. and Japan validates and calibrates the instrument and data products. The U.S. science team is located at NASA’s Jet Propulsion Laboratory.

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