Satellite images

Satellite imagery are photographs of Earth or other planets made from artificial satellites. First satellite photographs of Earth were made April 1, 1960 by the weather satellite TIROS-1. First satellite photographs of the Moon might have been made on October 6, 1959 by the Soviet satellite Luna 3, on a mission to photograph the far side of the Moon. In 1972 the United States started the Landsat program, the largest program for acquisition of imagery of Earth from space. Landsat 7, the most recent Landsat satellite, was launched in 1999. All satellite images produced by NASA are published by Earth Observatory and are freely available to the public. Other countries have their own satellite imaging programs. There are also private companies that provide commercial satellite imagery. Satellite images have many applications in agriculture, geology, forestry, regional planning, education, intelligence and warfare. Images can be in visible colours and in other spectra. There are also elevation maps, usually made with by radar imaging. Blue Marble was a project for mapping the visible color of the Earth with about 1-km resolution. The beautiful resulting images have become very popular in the media and among the public. A satellite can only see a relatively small area at the same time. For this reason mapping a large area (or the whole Earth) takes a lot of time and most satellite images are on average several years old. Because imaging satellites are in low Earth orbits, real-time imaging of a certain area is complicated. However, spy satellites can do this during wars and other military operations or to provide data for intelligence agencies. Still, the troops frequently find out that the ground truth is different from the images that were taken some time ago. The image resolution of satellite images varies. For most cities in the world photos with resolution of 10 meters or better are available. For areas outside cities the resolution can be 100-500 meters. Most of the Earth is imaged with resolution of 1 km or better. For many smaller areas images with resolution as high as 10 cm can be available. Satellite imagery is supplemented with aerial photography, which has higher resolution, but is more expensive per square meter. Because the total area of the land on Earth is so large and because resolution is relatively high, satellite databases are huge. Storing and serving satellite imagery was a big technical challenge. Satellite imagery can be combined with GIS data. For example, the EarthViewer can combine the images with maps and other information from various sources. In the early 21st century satellite imagery became widely available when affordable, easy to use software with access to satellite imagery databases is offered by several companies and organizations. In 2005 the Australian company Astrovision announced plans to provide real-time live satellite feeds, with down to 250 metres resolution over Australia. In weather, one drawback of using satellite imagery is how the images dissipate without the sun's presence. When viewing a satellite image, meteorologists often turn to other images such water vapour imagery or radars to check for precipitation and cloud formation. Added November 29, 2005 Satellites have there use, however due to the distance from the object viewed the resolution is limited. Soon a new type of satellite called a Stratellite will improve imagery as well as communications. These are placed at 65,000 feet and are expected to remain airborne for months. See this link for more information. Stratellite See also Object Oriented Image Classification (of Satellite Imagery) SRTM MODIS GLOBE Virtual globe NASA World Wind Virtual Earth Google Earth TerraServer-USA Terraserver.com Google Maps External links Blue Marble - the most detailed true-color image of the entire Earth to date. World Wind - an open source 3D Earth-viewing software developed by NASA that accesses NASA JPL database Google Earth - Google's commercial 3D Earth-viewing software- Free. Google Maps satellite imagery TerraServer-USA - formerly Microsoft TerraServer, a repository of free satellite images of the United States GlobeXplorer - library of satellite imagery and mapsde:Satellitenbild Search Term: "Satellite_imagery" Categories: Satellites | Photography by genre

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