What is Remote Sensing?
The word “remote sensing” was initially used in the 1950s in the USA by Ms. Evelyn Pruitt worked for the U.S. Office of Naval Research.
Remote sensing technology is used to summon information and understanding about an object while dealing with any physical contact.
This is a modern technology that started when the camera was invented for the first time. Did you know that the idea of taking the still photographs of Earth for the objective of topographic mapping surfaced in the middle of the 1840s?
At the time of World War 1, cameras were used on aero-planes to avail the best aerial view of lands which initiates an insurgency in military science. Satellite remote sensing was improved during the earlier space age.
These cameras were used for viewing Earth’s surfaces, for supplying the vivid details about Earth’s forests, lands, lakes, rivers, mountains, etc. for mapping.
Remote Sensing Explained
As we studied earlier, remote sensing is science-filled with technology that helps to gather data and to analyze a body without making any kind of physical contact.
This technology is vastly used in sectors like hydrology, geography, ecology, glaciology, oceanology, geology.
A tool known as the geographic information system is utilized for analyzing and mapping the Earth’s feature events. The GIS technology and remote sensing collect significant database operations, such as statistical analysis and query, through the map.
The GIS conducts to collect information on different locations and aids tools for displaying and analyzing for the calculations of population, economic development, its characteristics, and undergrowth.
All these functions build GIS separate from other systems and establish it for the wide range use of private and public remote sensing applications. These applications are for planning and forecasting outcomes generated from remote sensing satellites.
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Fundamentals of Remote Sensing
As we know all about remote sensing, let’s discuss its fundamentals. A remote sensing system works with the help of a detector for sensing the reflected or emitted energy from the surface of the Earth. It may be modified by the interposing atmosphere.
The sensor is available on a drone, satellite, or aircraft. The sensor converts the energy into a voltage form. This sensor is an analog to digital converter changes to a single integer value (known as Digital Number, or DN) for the energy.
The DN can be stored directly with the help of a digital detector. Only then can we display this value with an exact color to create an image of that region sensed by the system.
The DN defines the energy sensed with the help of a sensor in a particular part of the emitted or reflected from a particular region of that electromagnetic spectrum.
Sonar imagery also applies these principles, most helpful in the water where sound barges readily, whereas electromagnetic energy breaks quickly.
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Types of Sensors in Remote Sensing
The remote sensing can be differentiated into two types, they are:
Active, and
Passive
Those who put their source of energy (a large “flashbulb”) are called an active system.
Those who use solar energy emitted by the surface or reflected from the surface
Four things are being considered for satellite resolution, such as radiometric, spectral, spatial, and temporal resolution.
In a remote sensing system, electromagnetic radiation and the atmosphere controls many things. The characteristics of the imagery can be easily determined by satellite orbits.
The photo shows what satellite sees and how many times it returns to its original position.
The important design of remote sensing systems is the signal to noise ratio.
The following points are some essential elements for remote sensing;
An object or target
A stand to hold the instrument
A sensor for the observation of the target
What is Remote Sensing Satellite?
The technology is dependent on detecting and analyzing the physical phenomenon of an area by calculating its emitted or reflected radiation at a distance from satellite or aircraft.
Some enhanced cameras are specialized for sensing images, which offer clarity about the Earth to the researchers.
Some of the Examples Are
Satellites and planes are using the best cameras to capture images of large areas on the surface of Earth. It allows researchers to visualize even better than standing upon the ground.
Sonar systems available on ships can be used to capture images of the ocean floor without traveling to its bottom.
Satellites’ cameras can be used to create images of temperature differences in the ocean.
FAQs on Remote Sensing
1. What is remote sensing?
Remote sensing is the science and technology of acquiring information about the Earth's surface, an object, or a phenomenon without making any physical contact. This is achieved by sensing and recording reflected or emitted energy from sensors typically mounted on platforms like satellites or aircraft.
2. What are the two main types of remote sensing?
The two primary types of remote sensing are based on the source of energy:
- Active Remote Sensing: In this type, the sensor emits its own source of energy (like a radar pulse) towards the target and then detects the radiation that is reflected back from that target.
- Passive Remote Sensing: This type relies on detecting natural energy, primarily solar radiation, that is reflected or emitted from the Earth's surface. A standard camera taking a photograph is a simple example of a passive sensor.
3. What is the key difference between active and passive remote sensing?
The fundamental difference lies in the energy source. An active system provides its own energy (e.g., RADAR, LiDAR) to illuminate the object it is observing. A passive system depends on an external source, like the Sun, to provide the energy that it detects. Consequently, active systems can operate day or night, while many passive systems are limited to daytime use.
4. What are some important applications of remote sensing?
Remote sensing has a wide range of applications across various fields, including:
- Environmental Monitoring: Tracking deforestation, monitoring water quality, and observing the effects of climate change like melting ice caps.
- Disaster Management: Assessing damage from floods, wildfires, and earthquakes, and monitoring volcanic eruptions or dust storms.
- Urban Planning: Mapping urban growth and changes in land use over time.
- Agriculture: Monitoring crop health, estimating yields, and managing irrigation.
- Geology: Mapping geological formations and exploring for minerals and fossil fuels.
- Meteorology: Predicting weather by observing cloud patterns and movements.
5. What are the essential elements of a remote sensing system?
A complete remote sensing system involves several key elements working in sequence:
- An Energy Source to illuminate the target.
- Radiation and the Atmosphere, as the energy travels from its source to the target and then to the sensor.
- Interaction with the Target, where the energy is reflected or emitted.
- A Sensor to collect and record the electromagnetic radiation.
- Transmission, Reception, and Processing systems to convert the recorded energy into usable data.
- Interpretation and Analysis by experts to extract meaningful information.
6. How does electromagnetic radiation play a crucial role in remote sensing?
Electromagnetic radiation (EMR) is the foundation of remote sensing. Different materials on the Earth's surface—such as water, soil, and vegetation—reflect, absorb, and emit EMR in unique ways. These unique patterns are called spectral signatures. Remote sensors are designed to detect these signatures across various parts of the electromagnetic spectrum (e.g., visible, infrared, microwave), allowing scientists to identify and differentiate objects and features from space.
7. What are the different stages involved in the remote sensing process?
The remote sensing process typically follows seven distinct stages: 1) Energy source illumination, 2) Radiation interaction with the atmosphere, 3) Interaction with the target on the ground, 4) Recording of energy by the sensor, 5) Transmission and processing of the data from the sensor to a ground station, 6) Interpretation and analysis of the data image, and 7) Application of the extracted information to solve a problem.
8. How do Remote Sensing and GIS work together?
Remote Sensing and Geographic Information Systems (GIS) are complementary technologies. Remote Sensing is focused on data acquisition—it captures images and data about the Earth's surface. GIS is a computer-based system used to store, manage, analyse, and visualise this spatial data. In essence, remote sensing provides the raw input (the 'what' and 'where'), and GIS provides the platform to analyse this data and create meaningful maps and insights.
9. What do the different types of resolution mean in remote sensing?
Resolution in remote sensing describes the level of detail a sensor can capture, and it is defined in four ways:
- Spatial Resolution: Refers to the size of the smallest object that can be seen on an image. Higher resolution means more detail.
- Spectral Resolution: Describes the sensor's ability to detect different wavelengths in the electromagnetic spectrum. More bands allow for more specific identification of materials.
- Temporal Resolution: Indicates how often a sensor collects imagery of the same area. High temporal resolution is vital for monitoring dynamic events like floods or crop growth.
- Radiometric Resolution: The sensor's ability to distinguish between small differences in the intensity of reflected or emitted energy, affecting the number of shades of grey or colour in an image.
10. Why is remote sensing considered a revolutionary technology for monitoring Earth's changes?
Remote sensing is revolutionary because it provides a consistent, large-scale, and repeatable method for observing our planet that is impossible with ground-based methods alone. It allows scientists to monitor global and regional trends over decades, such as deforestation, urban sprawl, glacial retreat, and agricultural patterns. This capability is crucial for understanding the impact of human activities and natural processes on the Earth's systems and for making informed policy decisions.
