Jawaharlal Nehru Technological University Hyderabad B.Tech II MINE SURVEYING Previous Question Paper (October - 2020 - R18)

In remote sensing, the scale represents the ratio of a distance on the image or map to the corresponding distance on the ground. It is a critical parameter that determines the level of detail and the spatial extent of the captured data.

The scale is mathematically defined as:

Where f is the focal length of the camera or sensor lens and H is the flying height of the platform above the ground. A larger scale (e.g., 1:5,000) provides higher spatial resolution, allowing for the identification of smaller features, while a smaller scale (e.g., 1:50,000) covers a larger geographical area but with less detail. In satellite remote sensing, scale is often expressed as the Ground Sample Distance (GSD), which indicates the physical size of one pixel on the ground.

Electromagnetic Radiation (EMR) is the fundamental energy source for most remote sensing systems. It consists of an electric field and a magnetic field oscillating perpendicular to each other and to the direction of wave propagation. EMR travels at the speed of light and is characterized by its wavelength (λ) and frequency (ν).

The relationship is given by:

Where c is the speed of light. In remote sensing, the Electromagnetic Spectrum is divided into specific regions based on wavelength, including the Visible (0.4–0.7 μm), Infrared (Near, Mid, and Thermal), and Microwave regions. Sensors detect EMR that is either reflected from the Earth's surface (passive remote sensing, such as sunlight) or emitted by the Earth (thermal infrared). The interaction of EMR with the atmosphere and surface features—through absorption, scattering, and reflection—is what allows sensors to distinguish between different land covers, minerals, and environmental conditions.