Components of Remote Sensing

Components of Remote Sensing (RS)

• The remote sensing process involves six components: Energy Source or Illumination (A), Interaction with the Atmosphere (B), Interaction with the Target (C), Recording of Energy by the Sensor (D), Transmission, Reception, and Processing (E), Interpretation and Analysis (F), and Application (G)

Remote Sensing Process

• Recording of Energy by the Sensor (D): a sensor is required to collect and record the electromagnetic radiation reflected or emitted from the target
• Transmission, Reception, and Processing (E): the energy recorded by the sensor is transmitted to a receiving and processing station where the data are processed into an image
• Interpretation and Analysis (F): the processed image is interpreted to extract information about the target
• Application (G): the extracted information is applied to better understand the target, reveal new information, or assist in solving a particular problem

Applications of Remote Sensing

• Remote sensing is useful for various applications in urban planning and transportation, natural resource mapping, and more

Electromagnetic Energy (EM)

• Electromagnetic energy is a form of energy that travels in a harmonic sinusoidal wave pattern
• It has both electric and magnetic components that oscillate perpendicular to each other and perpendicular to the direction of energy propagation
• EM energy can be described in terms of its velocity, wavelength, and frequency
• The velocity of EM energy is approximately 3 × 10^8 m/s, wavelength is typically expressed in micrometers (μm), and frequency is expressed in Hertz (Hz)

Electromagnetic Radiation Spectrum

• The EM spectrum ranges from gamma rays with very short wavelengths to radio waves with very long wavelengths
• The visible region occupies a small range between 0.4 and 0.7 μm, while the infrared (IR) region spans between 0.7 and 100 μm
• The EM spectrum is divided into regions or intervals of different wavelengths, denoted by different names

Passive and Active Remote Sensing

• Passive remote sensing uses natural energy sources such as the Sun, while active remote sensing provides its own energy source for illumination
• Examples of active remote sensing include radar and lidar

Sensor Definition

• A sensor is a device that detects and responds to some type of input from the physical environment
• In remote sensing, a sensor is a device that gathers electromagnetic energy and presents it in a form suitable for obtaining information about the object under investigation

Sensor Types

• Optical sensors primarily operate within the visible spectrum and are used to create images of the Earth's surface
• Radar sensors utilize micro or radio waves to determine the range, angle, or speed of objects and create high-resolution images of the Earth's surface

Sensor Platforms

• Platforms can be ground-based, air-borne, or space-borne
• Ground-based platforms are used for close-range characterization of objects and have high spatial resolution
• Air-borne platforms are used to obtain images of the Earth's surface and have high spatial resolution (20 cm or less)
• Space-borne platforms are used to cover large areas and have repetitive coverage of an area of interest

Energy Interactions with Earth Surface Features

• Reflection: incident energy is redirected in such a way that the angle of incidence is equal to the angle of reflection
• Spectral reflectance: the ratio of energy reflected by the surface to the energy incident on the surface, measured as a function of wavelength
• Spectral reflectance curves: graphical representation of the spectral response of an object over different wavelengths of the electromagnetic spectrum, used to gain insight into the spectral characteristics of different objects