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Satellite Remote Sensing is a Valuable Tool for Modern Scientific Research Topics.
Remote means far away and sensing means to find out, so remote sensing meaning is to find out information about faraway areas without physical contact. The term Satellite remote sensing was first used by Ms. Evelyn Pruitt in the 1950 s. . Satellite remote sensing is a valuable tool for modern scientific research topics, with the help of this technology researcher gathered important data of physical characteristics of an area of the earth without physical contact, for example; Remote sensing in geology allows mapping of the geological feature of remote areas. There are two types of remote sensing Active remote sensing and Passive remote sensing. Active remote sensing is a type of remote sensing in which Satellite or Aircraft provide their source of illumination and gathered data, while in the case of Passive remote sensing no satellite or aircraft provides their source for illumination they have been gathered data in naturally available energy like the sun.
Role of Electromagnetic Spectrum in Remote Sensing
Remote sensing is a technology based on different electromagnetic energy, Various satellites recognized and measure different energies of the electromagnetic spectrum. The electromagnetic spectrum is divided into seven important categories including Gamma Rays, X-Rays, Ultraviolet (UV), Visible light, Infrared, Microwaves, Radio Waves.
1.Gamma Rays (Wavelength < 10-12 meters)
Gamma rays have the highest frequency and highest energy and these have the shortest wavelength these are formed by the hottest bodies in the universe and our atmosphere has been protected us from these rays because these are biologically not good for us.
2.X-Rays (Wavelength 10-8 to 10-12 meters)
X-rays travel through various materials and they have been used for medical purposes, like gamma rays they also never come to the earth because of the atmosphere.
3.Ultraviolet (UV) (Wavelength 10-7 - 10-8 meters)
Sun is a source of ultraviolet rays, these are harmful rays, but our atmosphere protects us from these rays by absorbing them completely.
4.Visible (Wavelength ~ 10-7 meters)
The visible portion of the spectrum ranges from approximately 0.4µm to 0.7µm, Visible light is only part of the spectrum that can be seen by the human eye and it is very important for remote sensing, and energy is recorded by photography.
5.Infrared (Wavelength ~ 10-6 to 10-3 meters)
Infrared rays cover 0.75 µm to 100 µm (750 nm - 10,000 nm) in wavelength, these rays are classified into three types Near Infrared (NIR): 0.7 – 1.3µm, Shortwave Infrared (SWIR): from 1.3 – 3 µm and the Far or Thermal Infrared from 3 - 100 µm. Infrared radiation has been widely used in remote sensing for different analyses.
6.Microwaves (Wavelength ~ 10-3 to 10-1 meters)
These are high-frequency waves that are important for satellite communication and being helpful to discover the earth phenomena.
7.Radio Waves (Wavelength >10-1 meters)
Radio waves are carrying the longest wavelength in the electromagnetic spectrum, radio waves are being widely used in wireless networking, television, amateur radio.
Color-Infrared (CIR) Aerial Photography
Colored infrared Aerial photography has been done by many satellites and these images shows false colors because which features are showing normally cannot seen by human eye ,including interpretation of natural resources, vegetation moisture content monitoring, surface temperature, vegetation stress monitoring, soil moisture monitoring, cloud differentiation, volcanic monitoring mineral and rock discrimination.In color-infrared photography dark red shows dense vegetation and lighter tone of red and pink represent decrease of vigor vegetation. In agricultural region bare soil shows white, blue, or green and their darker color represents rich in moisture content,While man-made features shows colour of the material from which they are made for example Asphalt roads shows dark blue or black colors,water shows dark blue or black color for clear wate ,shows pale blue for amount of sediment in it,white color show by shallow water containing sand.
Remote Sensing Satellites Data Quality
Remote sensing data satellite's quality depend on spatial, spectral, radiometric, and temporal resolutions.
Spatial resolution means that the human eye can see only specific details that have been captured by the satellite, if The satellite resolution is 30 m, Then the human eye never sees detail beyond 30 m, In other words, spatial resolution means a digital image carrying higher resolution has formed of the greatest number of pixels, while lower resolution Satellite image has been formed of the lower number of pixel.
Temporal resolution means acquired data of the same location in different periods. Landsat 7 satellite temporal resolution is 16 days.
The spectral resolution is also very important in remote sensing data, High spectral resolution gives clear identification and characteristics of data gives a fine interval of a wavelength of bands and lower resolution give extinct information of data.
The panchromatic image formed by a satellite whose sensor is very sensitive to capture wavelength of all colors of light is a single band image shows color white to black. Some modern satellite Like Quick Bird, Cartosat, and IKONOS has also formed panchromatic images and they are highly valuable due to their spatial resolution for example Quick bird produced 0.6 m panchromatic image, while multispectral image produced 2.4 m resolution.
Multispectral image shows small numbers of spectral band 3 to 15 and represents particular wavelength ranges of the electromagnetic spectrum.
Hyperspectral image shows hundreds of spectral bands and gives large identification of characteristics of data .these images are very useful in various fields of research.
It plays a vital role in remote sensing data, it is the potential of the sensor to give a difference between grey scale value while give measuring in a bit, larger the number of bits can store large grey scale values.
Important Remote Sensing Satellites
The object in space that moves in a circular path around a big object is known as a satellite, While satellites are categorized into two types natural and artificial, moon moves around the earth are natural satellite while many artificial satellites have launched by many countries list of important remote sensing satellites are given below. Ikonos ,Landsat 8,Quick bird,Landsat 7,IRS-1 A,Resources at-1,Envisat,Terra,Advanced land observation satellite,TerraSAR-X,Oceansat-1,Oceans-2,IRS-1 C,Cartosat-1,Cartosat-2,Landsat-5,IRS-1D,IRS-P3,Landsat-1,Earth observing-1,IMS-1,Aqua,IRS-P2, ADEOSI,Cartosat-2A, WorldView-2,WorldView-3,Landsat-4,SARAL,WorldView-1
Hogg,A., Potter,B. 2018 . Wetland and Stream Rapid Assessments . Reterived from .www.sciencedirect.com › earth-and-planetary-sciences › in..
The Electromagnetic Spectrum .2015. Reterived from www.nrcan.gc.ca › remote-sensing-tutorials › introduction
This content reflects the personal opinions of the author. It is accurate and true to the best of the author’s knowledge and should not be substituted for impartial fact or advice in legal, political, or personal matters.
© 2020 Ambreen Behzad
Ambreen Behzad (author) from Karachi,Pakistan on November 14, 2020:
Remote Sensing is an important subject, hope this article will help to understand remote sensing fundamentals.