Global Scan Technologies, Dubai
The term, “remote sensing,” was first introduced in 1960 by Evelyn L. Pruitt of the U.S. Office of Naval Research. Over the past decade, a renewed and expanding interest in practical applications of Earth observations from space and airborne platforms has coincided with and been fueled by changes in the data, in how they can be used, and in who produces them. There have been significant improvements in the availability of remote sensing data from India, US and France in the spectral and spatial resolution. In addition, the data can be adapted for more varied uses because of the extension and advancement of complementary spatial data technologies, such as GIS and the GPS, which can be used in conjunction with remote sensing data.
HIGH RESOLUTION OPTICAL REMOTE SENSING
Optical remote sensing makes use of visible, near infrared and short-wave infrared sensors to form images of the earth’s surface by detecting the solar radiation reflected from targets on the ground. Different materials reflect and absorb differently at different wavelengths. Thus, the targets can be differentiated by their spectral reflectance signatures in the remotely sensed images. Optical remote sensing systems are mainly classified Panchromatic, Multispectral, and Hyper spectral depending on their spectral resolution.
NASA – LANDSAT
Landsat satellites have been collecting images of the Earth’s surface for more than thirty years. NASA launched the first Landsat satellite in 1972, and the most recent one, Landsat 7, in 1999. Instruments onboard the satellites have acquired millions of images of the Earth. These images provide a resource for global research. It has the following the sensors.
The Multispectral Scanner (MSS)
It was a sensor onboard Landsats 1 through 5 and acquired images of the Earth nearly continuously from July 1972 to October 1992, with an 18- day repeat cycle for Landsats 1 through 3 and a 16-day repeat cycle for Landsats 4 and 5.Landsat MSS image data consisted four spectral bands , although the specific band designations changed between Landsats 1-3 and Landsats 4-5. The resolution for all bands of 79 m, and approximate scene size is 170 km northsouth by 185 km east-west (106 mi by 115 miles).
The Thematic Mapper (TM)
It is a sensor carried onboard Landsats 4 and 5 and has acquired images of the Earth from July 1982 to the present, with a 16-day repeat cycle.Landsat TM image data consists of seven spectral bands with a spatial resolution of 30 meters for bands 1 to 5 and band 7.
Spatial resolution for band 6 (thermal infrared) is 120 meters, but band 6 data are oversampled to 30 meter pixel size. Approximate scene size is 170 km north-south by 183 km eastwest (106 mi by 114 mi).
Enhanced Thematic Mapper Plus (ETM+)
It consist of eight spectral bands, with a spatial resolution of 30 meters for bands 1 to 5 and band 7. Resolution for band 6 (thermal infrared) is 60 meters and resolution for band 8 (panchromatic) is 15 meters. Approximate scene size is 170 km north-south by 183 km east-west (106 mi by 114 mi).
High Resolution Remote Sensing Sensors SENSORS