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Remote sensing is the process of gathering information, detecting, evaluating, and monitoring the physical characteristics of a region by recording the reflected and emitted radiation energy without making direct contact with the object under investigation.
- This is carried out by catching reflected radiation/energy.
- The word remote sensing refers specifically to gathering knowledge about Earth and other planets.
- Remote sensing is used in a variety of fields, including geophysics, geography, land surveying, and the majority of Earth science disciplines (for example, exploration geophysics, hydrology, ecology, meteorology, oceanography, glaciology, geology)
- It also has military, intelligence, commercial, economic, planning, and humanitarian applications, among others.
There are two types of remote sensing methods: Passive remote sensing and Active remote sensing.
- Passive sensors collect radiation produced or reflected by the objects or their surroundings.
- The most common source of radiation recorded by passive sensors is reflected sunlight.
- Film photography, infrared, charge-coupled devices, and radiometers are examples of passive remote sensors.
- Active remote sensing, on the other hand, produces energy to scan objects and spaces, after which a sensor detects and measures the reflected or reflected radiation from the target.
- Active remote sensing techniques such as RADAR and LiDAR measure the time delay between emission and return to determine an object's position, speed, and direction.
Very Short Answers Questions [1 Mark Questions]
Ques. What is meant by remote sensing?
Ans. A remote sensing technique detects and monitors the physical properties of an area by calculating its emitted and reflected radiation from a distance (usually from an aircraft or satellite). It is a collection of knowledge about a phenomenon or objects without having direct touch with the objects being studied.
Ques. How did remote sensing start?
Ans. With the introduction of aerial flight, the modern type of remote sensing developed. G. Tournachon, a balloonist, was an early proponent of aerial photography. While flying in his balloon, he produced images. In the early phases, distant photographs were captured using kits, unmanned balloons, and rockets.
Ques. Remote sensing uses which of the following in its applications?
- Electric wave
- Gamma rays
- Sonar waves
- Electromagnetic waves
Ans. The correct answer is d. Electromagnetic waves
Explanation: Electromagnetic radiation is used in remote sensing technology.
Ques. What are the two types of remote image-sensing technology?
Ans. The technique may be divided into two categories: active remote sensing and passive remote sensing. They are primarily distinguished by the medium through which they obtain the desired information.
Ques. What is meant by RADAR?
Ans. Radar is a type of radiolocation system that uses radio waves to calculate the distance (ranging), angle (azimuth), and radial velocity of objects in relation to a given location. The term RADAR acronym for Radio Detection and Ranging.
Short Answers Questions [2 Marks Questions]
Ques. What are the uses of remote image sensing in the study of oceans?
Ans. Remote sensing is commonly used to detect and map the topography of the ocean floor. Remotely sensed images may easily discover and study hidden undersea deep canyons, mountain ranges, and magnetic activity.
Ques. What are the specific uses of remote image sensing in the case of weather?
Ans. Remote sensing may be used to track and analyze clouds. It enables meteorologists to forecast and study weather patterns, volcano eruptions, marine movements, and other phenomena.
Ques. What is meant by active remote sensing?
Ans. An active remote sensing system uses a man-made source of radiation for inspection. The signal that is produced returns to the sensor and describes the Earth or the atmosphere. The two primary types of active remote sensing are LiDAR and RADAR. Both send out radiation beams from a sensor and figure out how much radiation is dispersed back at the sensor.
Ques. What is meant by passive remote sensing?
Ans. The passive remote sensing technique relies on solar radiation as the source of illumination for it to function. The most popular sensors for this type of remote sensing are those with hyperspectral and multispectral capabilities. It primarily concentrates on the visible, near-infrared, and shortwave infrared spectral ranges.
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Long Answers Questions [3 Marks Questions]
Ques. What are the passive remote sensing devices?
Ans. The most common types of passive remote sensing devices are radiometers and spectrometers.
- A spectrometer is a device that separates and analyses spectral bands.
- A radiometer measures the amount of radiation emitted by an item in specific band ranges (visible, infrared, microwave).
- The power of radiation in various band ranges is measured using a spectroradiometer.
- The most precise sort of passive sensor utilized in remote sensing is employed in hyperspectral radiometers. It distinguishes hundreds of very small spectral bands within the visible, NIR, and MIR ranges due to its extraordinarily high resolution.
- An imaging radiometer scans an object or a surface to create an image.
- Changes in speed per unit of time (e.g., linear or rotational) are detected by an accelerometer.
Ques. What are the active remote sensing devices?
Ans. In remote sensing, each active sensor delivers its signal to the object and then examines the response - the received quantity.
- A radar is a sensor that helps in radio signal range. Its distinguishing characteristic is the antenna that emits impulses. When the energy flow in radar active remote sensing encounters an impediment, part of it scatters back to the sensor. It is feasible to determine the target's distance based on its size and trip duration.
- Lidar uses light to calculate distance. Lidar active remote sensing involves sending light pulses and measuring the amount recovered. By multiplying the time by the speed of light, the target location and distance are calculated.
- A laser altimeter measures elevation with lidar.
- With a ranging instrument, one or two identical devices on separate platforms transmit signals to estimate the range.
- An active sounder is a device that emits impulses in order to study the weather conditions vertically.
- A scatterometer is a device that measures reflected (backscattered) radiation.
Ques. What are the science fields that depend on remote sensing?
Ans. Remote sensing is used to collect information about the Earth and other solar planets. Remote sensing is used in a variety of domains such as ecology, hydrology, geology, meteorology, geography, oceanography, glaciology, and so on. It has also been used in intelligence, economics, planning, and the military.
Very Long Answers Questions [5 Marks Questions]
Ques. What are the primary applications of remote sensing?
Ans. The primary applications of remote sensing are
- Analyzing the condition of rural roads: Rural road conditions may now be analyzed with inch-by-inch precision utilizing various GIS and Remote Sensing methods. It saves transporters a lot of time and money.
- Collecting Earth’s pictures from space: Many space organizations have collections of photographs of the Earth. It contains interesting patterns of Earth's geometry, including the atmosphere, oceans, land, and so on. This information is gathered by EO-1, Terra, and Landsat satellites.
- Creating a base map for visual reference: Many present mapping systems, such as Google Maps, open street maps, Bing Maps, NASA's Globe View, and others, are based on remote sensing.
- Detecting land use and land cover: Remote sensing technologies are used to identify the physical characteristics of land as well as how it is used (land use).
- Estimating forest supplies: Because forests are a source of important goods such as paper, packaging, and construction materials, MODIS, AVHRR, and SPOT are frequently employed to measure the increment/decrement in global forests.
Ques. What are the applications of remote sensing in agriculture?
Ans. The following are the applications of remote sensing used in agriculture
- Identifying crop conditions: Global food supply is monitored using satellite images and normalized difference vegetation index (NDVI) technology. Healthy agricultural regions are green, whereas other parts are red or blue.
- Increasing precision in farming: Crop health may be assessed using remote sensing techniques, saving about 10% of fertilizer, money, and time.
- Determining the soil moisture content: A satellite's active and passive sensors in orbit are used to estimate soil moisture content. Many earth sciences, such as water cycle, flood, and drought, depend on soil moisture content.
- Crop production forecasting: Remote sensing is used to forecast agricultural output and yield across a certain field, as well as how much of the crop will be harvested under the given conditions. The researcher can forecast the amount of crop produced in a certain land during a given time period.
- Determining crop damage and crop progress: Remote sensing technology may be used to penetrate farmland and detect exactly how much of a certain crop has been damaged or under stress, as well as the status of the remaining crop on the farm, in the case of crop damage or crop progress.
Ques. What is spectral reflectance in remote sensing?
Ans. Many applications require land-cover and land-use maps, including regional planning, landscape planning, landscape ecology, agricultural management, and forestry.
- Electromagnetic energy from the Sun is reflected, absorbed, or transmitted when it reaches the Earth's surface.
- A fundamental assumption in remote sensing is that specific study targets (different types of soils, water with varying degrees of impurity, rocks with varying lithologies, or vegetation of various species) interact with incident radiation in a unique and characteristic manner, which is described by the spectral response of that study target.
- Many factors can influence spectral reflectance, including soil nutrients, vegetation development stage, and soil color (which can be influenced by recent weather conditions).
- In certain cases, the interaction between incoming radiation and the earth's surface object will change over time, as may be predicted with vegetation as it progresses from the leafing stage to mature growth and, eventually, senescence.
- The term ‘spectral signature’ is frequently used to characterize a research target's spectral response curve.
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