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Electromagnetic Spectrum

Electromagnetic Spectrum EMR is a form of energy exhibiting wave-like behaviour as it travels through space. EMR ranges from very high energy radiation such as gamma rays and X rays through ultraviolet light, visible light, infrared radiation and microwaves to radio waves. The range of frequencies of EMR is known as the electromagnetic spectrum. The Sun produces a continuous spectrum of energy from gamma rays to radio waves that continually bathe the Earth in energy. The visible portion of the spectrum may be measured using wavelength (measured in mm or nm) or electron volts (eV) - All units are interchangeable. Classification of Electromagnetic Radiation Infrared radiation (750 nm - 1 mm) The infrared region can be divided into two categories based on their radiation properties - the reflected IR, and the emitted or thermal IR. The reflected IR covers wavelengths from approximately 0.7 micrometres to 3.0 micrometres. The thermal IR covers wavelengths from approxima

Electromagnetic Radiation

Electromagnetic Energy Interactions When the energy being remotely sensed comes from the Sun, the energy: Propagates through the vacuum of space Interacts with the Earth's atmosphere, surface, and atmosphere (reflected, absorbed, transmitted); Reaches the remote sensor (interacts with various optical systems, filters, emulsions, or detectors); Electromagnetic Radiation Transfer of energy from one body to another in the form of electromagnetic waves is referred to as Electromagnetic Radiation. To understand how electromagnetic radiation is created, how it propagates through space, and how it interacts with other matter, it is useful to describe the processes using two different models popularly known as Electromagnetic Radiation Models: the wave model; the particle model Wave Model of EM Energy An electromagnetic wave is composed of electric and magnetic vectors that are orthogonal to one another and travel from the source at the speed of light. Prope

Basic of Remote Sensing V

How is Energy Transferred? The energy can be transferred in the three basic ways: conduction, convection, and radiation. The transfer of energy by electromagnetic radiation (EMR) is of primary interest to remote sensing because it is the only form of energy transfer that can take place in a vacuum (the region between the Sun and the Earth). The Sun bathes the Earth’s surface with radiant energy causing the air near the ground to increase in temperature. The less dense air rises, creating convectional currents in the atmosphere. Energy may be conducted directly from one object to another as when a pan is in direct physical contact with a hot burner. Energy Interactions When Electro-Magnetic (EM) energy is incident on any given earth surface feature, three fundamental energy interactions are possible. Reflection (ER) Absorption (EA) Transmission (ET) Incident Energy (EI) = reflected energy + transmitted energy + absorbed energy Three forms of Interactio

Basic of Remote Sensing IV

Sources of Electromagnetic Energy There are three main sources of electromagnetic radiation that are used in remote sensing: Solar radiation (natural radiation from the sun) Terrestrial radiation (natural radiation emitted by Earth's surface) Artificial radiation (from a remote sensing system) Solar Radiation The Sun yields a continuous spectrum of EM energy. This Incident radiation can be reflected from the Earth's surface. This process produces a large amount of short wavelength energy (from 0.4 - 0.7 µm; blue, green, and red light). It can also be emitted by the Earth's surface. Such emitted radiation is typically of a longer wavelength, in the middle and far infra-red wavelengths. Interacts with the atmosphere and surface materials (reflect, absorb). Since the Sun has a much higher temperature (6000 degrees K) than the Earth (303 degrees K), so the overall energy radiated by the Earth is lower and has its peak at a longer wa

Basic of Remote Sensing III

Contents Advantages Limitations Applications Advantages of Remote Sensing : Provides a synoptic view over a large region; Offers Geo-referenced information and digital information; Most of the remote sensors operate in every season, every day, every time and even in tough weather; Limitations : Can be expensive; Can be technically difficult; Not direct; Measure surrogate variables e.g. reflectance (%), brightness temperature, backscatter; Applications of Remote Sensing Urban & Regional Planning Scope: Mapping & updation of city/town maps Urban sprawl monitoring Town planning Facility management GIS database development Benefits: Better decision support, planning & management Rapid information updation Infrastructure development monitoring Spatial information analysis Agriculture Scope: Crop acreage estimation Crop modeling for yield & production forecast / estimation Crop & Orchard monitoring Soil sensing Mapping

Basic of Remote Sensing II

Remote Sensing Process A. Energy Source or Illumination – the first requirement is to have an energy source which illuminates or provides electromagnetic energy to the target of interest. B. Radiation and the Atmosphere – as the energy travels from its source to the target, it will come in contact with and interact with the atmosphere it passes through. This interaction may take place a second time as the energy travels from the target to the sensor. C. Interaction with the Target – once the energy makes its way to the target through the atmosphere, it interacts with the target depending on the properties of both the target and the radiation. D. Recording of Energy by the Sensor – after the energy has been scattered by, or emitted from the target, we require a sensor to collect and record the EMR. E. Transmission, Reception, Processing – the energy recorded by the sensor has to be transmitted, often in electronic form, to receiving and processing station where the data a