Remote Sensing and Geographical Information System
Define and classify Remote Sensing
Remote sensing refers to the collection of data about an object or phenomenon from a distance, without making physical contact with the object. Remote sensing is classified into two main categories: active remote sensing and passive remote sensing.
Active remote sensing involves the use of an energy source to illuminate the target, such as radar or lidar. The sensor then measures the reflection or backscattered energy from the target to generate data.
Passive remote sensing relies on the natural energy emitted, reflected, or backscattered by the target. Examples of passive remote sensing include optical remote sensing with instruments like cameras or multispectral sensors, and microwave remote sensing with instruments like radiometers.
Both active and passive remote sensing have various applications in fields such as environmental monitoring, agriculture, geology, and military surveillance.
An idealised remote sensing system refers to a theoretical model of a remote sensing system that includes all the necessary components for capturing and processing data from a distance. This model is used as a benchmark to evaluate and compare actual remote sensing systems and their performance.
An idealised remote sensing system consists of a platform, a sensor, and a data processing system. The platform refers to the vehicle or device that carries the sensor and is responsible for positioning the sensor. The sensor is the component responsible for collecting data, which can be in the form of electromagnetic radiation, such as light or infrared radiation, or other forms of energy. The data processing system is responsible for receiving, analyzing, and storing the data collected by the sensor.
The idealised remote sensing system also includes a series of mathematical algorithms and models that are used to convert raw data into useful information. These algorithms and models are used to correct for atmospheric and environmental effects, remove noise and other sources of error, and extract meaningful information from the data.
In summary, the idealised remote sensing system is a theoretical model that includes all the necessary components for capturing and processing data from a distance and converting it into useful information.
The principle of remote sensing refers to the process of obtaining information about an object or phenomenon without making direct contact with it. This is accomplished by collecting data from a distance using various sensors, such as cameras, microphones, or radar. The information collected can be used to identify the object or phenomenon, determine its physical or chemical properties, or study its behavior.
Remote sensing works by detecting and measuring electromagnetic radiation that is reflected, emitted, or transmitted by an object or phenomenon. This radiation can be in the form of light, radio waves, microwaves, or infrared radiation. The type of radiation used and the type of sensor used depend on the specific remote sensing application.
Once the data is collected, it is processed, analyzed, and interpreted to obtain the desired information. The information gathered from remote sensing can be used to support a wide range of applications, such as mapping, environmental monitoring, agriculture, weather forecasting, and military intelligence.
Scattering refers to the deflection or spreading of light or other forms of electromagnetic radiation in all directions when it encounters an obstacle or a medium with different properties. It is a fundamental process that affects the behavior of light in different environments and is a critical component of remote sensing.
Classification of Scattering:
- Elastic Scattering: This occurs when the light is deflected or scattered by an object but retains its original wavelength and frequency, and thus, the energy of the light is conserved.
- Inelastic Scattering: This occurs when the light is scattered by an object and changes its wavelength, frequency, and energy.
- Rayleigh Scattering: This is a type of elastic scattering that occurs when light scatters off particles that are much smaller than the wavelength of light, such as air molecules. It is responsible for the blue colour of the sky during the day and the reddish colour during sunrise and sunset.
- Mie Scattering: This is a type of elastic scattering that occurs when light scatters off particles that are similar in size to the wavelength of light, such as water droplets in clouds.
- Rayleigh-Mie Scattering: This refers to the combination of Rayleigh and Mie scattering.
- Non-Selective Scattering: This occurs when light is scattered in all directions, including forward and backward scattering.
- Selective Scattering: This occurs when light is scattered preferentially in a specific direction, such as forward scattering.
Electromagnetic (EM) radiation refers to the energy that travels through space as electromagnetic waves, including visible light, ultraviolet (UV) radiation, X-rays, and gamma rays. When this radiation reaches Earth’s surface, it interacts in various ways, depending on the properties of the surface and the type of radiation.
One of the ways that EM radiation interacts with Earth’s surface is through absorption and reflection. Absorption occurs when the radiation is absorbed by the surface, and its energy is transformed into heat. This is more likely to happen with surfaces that have high levels of absorption, such as dark surfaces or those with high water content. Reflection, on the other hand, occurs when the radiation bounces back from the surface without being absorbed. This is more likely to happen with surfaces that are reflective, such as metal or glass.
Another way that EM radiation interacts with Earth’s surface is through transmission. This occurs when the radiation passes through the surface, rather than being absorbed or reflected. This is more likely to happen with surfaces that are transparent, such as air or water.
A third way that EM radiation interacts with Earth’s surface is through scattering. Scattering occurs when the radiation encounters small particles in the atmosphere and is redirected in different directions. This results in the radiation being dispersed, which can cause it to lose energy or change its wavelength. This is why the sky appears blue, as the blue light is scattered more than other colours.
Finally, EM radiation can also cause chemical reactions to occur on Earth’s surface. For example, UV radiation can cause chemical changes in materials, such as breaking down the molecules that make up plastics or causing mutations in living organisms. This is why it is important to protect against excessive exposure to UV radiation.
In conclusion, the interaction of EM radiation with Earth’s surface depends on the properties of both the radiation and the surface, and can involve processes such as absorption, reflection, transmission, scattering, and chemical reactions.
Remote sensing observing platforms refer to the various technologies and devices used to collect data and information about the Earth and its environment from a distance. These platforms play a crucial role in studying and understanding the Earth’s surface, atmosphere, and oceans.
- Satellites: Satellites are one of the most commonly used remote sensing platforms. They orbit the Earth at an altitude ranging from a few hundred kilometres to several thousand kilometres, and are equipped with sensors that can detect various forms of electromagnetic radiation, such as visible light, infrared radiation, and microwave radiation. Some examples of remote sensing satellites include Landsat, Sentinel, and MODIS.
- Aerial platforms: Aerial platforms, such as aeroplanes and drones, are equipped with sensors that can collect data and images of the Earth’s surface from the air. These platforms offer high-resolution images, and can be used to gather data in areas that are difficult to access by ground-based instruments or satellites.
- Ground-based platforms: Ground-based platforms refer to remote sensing instruments that are located on the ground, such as meteorological stations, radars, and lidars. These instruments are typically used to gather data about the Earth’s atmosphere, including temperature, precipitation, and wind speed and direction.
- Balloon platforms: Balloon platforms are unmanned balloons that are equipped with sensors and float at high altitudes in the atmosphere. These platforms offer a unique perspective for remote sensing, as they can gather data about the Earth’s atmosphere and climate from a distance.
In conclusion, remote sensing observing platforms are a diverse set of technologies and devices that are used to collect data and information about the Earth from a distance. These platforms play a critical role in understanding the Earth’s surface, atmosphere, and oceans and are critical tools for applications such as environmental monitoring, resource management, and disaster response.
A sensor is a device that converts a physical or chemical stimulus into an electrical signal that can be interpreted and analyzed. Sensors are used in a wide range of applications, including environmental monitoring, industrial processes, and consumer electronics.
Sensors can be classified based on the type of stimulus they detect and the type of output they produce. Some common classifications of sensors include:
- Optical sensors: These sensors detect light and are used to measure the intensity, colour, or direction of light. Examples of optical sensors include cameras, photodiodes, and photoresistors.
- Temperature sensors: These sensors detect changes in temperature and are used to measure the temperature of objects or environments. Examples of temperature sensors include thermistors, thermocouples, and resistance temperature detectors (RTDs).
- Mechanical sensors: These sensors detect mechanical stimuli such as force, pressure, and acceleration. Examples of mechanical sensors include accelerometers, pressure sensors, and strain gauges.
- Chemical sensors: These sensors detect changes in the chemical composition of a substance and are used to measure the concentration of chemicals or pollutants in the environment. Examples of chemical sensors include gas sensors, pH sensors, and biosensors.
- Magnetic sensors: These sensors detect changes in magnetic fields and are used to measure magnetic field strength, direction, and orientation. Examples of magnetic sensors include magnetometers, Hall effect sensors, and magnetoresistive sensors.
In conclusion, sensors are devices that convert physical or chemical stimuli into electrical signals that can be interpreted and analyzed. Sensors are classified based on the type of stimulus they detect and the type of output they produce, with common classifications including optical, temperature, mechanical, chemical, and magnetic sensors.
Remote sensing is a technology that uses sensors and platforms to collect data and information about the Earth’s surface, atmosphere, and oceans from a distance. Remote sensing plays a critical role in a wide range of applications, including:
- Environmental monitoring: Remote sensing is used to monitor and track changes in the Earth’s environment, such as land use changes, deforestation, and changes in vegetation patterns. This information is used to understand and address environmental problems such as climate change, deforestation, and loss of biodiversity.
- Natural resource management: Remote sensing is used to monitor and manage natural resources such as forests, water bodies, and minerals. This information is used to manage resources sustainably and prevent over-exploitation.
- Agriculture: Remote sensing is used to monitor crop health, yield, and productivity. This information is used to optimize crop management practices and improve agricultural productivity.
- Disaster response: Remote sensing is used to monitor and respond to natural disasters such as hurricanes, earthquakes, and tsunamis. This information is used to assess the extent of damage and direct relief efforts.
- Weather forecasting: Remote sensing is used to gather data about weather patterns and conditions, including temperature, precipitation, wind speed, and atmospheric pressure. This information is used to improve weather forecasting and help protect communities from severe weather events.
- Oceanography: Remote sensing is used to study and understand the world’s oceans, including the distribution and movements of marine life, ocean currents, and sea-surface temperature.
In conclusion, remote sensing is a critical technology that is used in a wide range of applications, including environmental monitoring, natural resource management, agriculture, disaster response, weather forecasting, and oceanography. The data and information collected by remote sensing is used to make informed decisions and improve our understanding of the Earth and its environment.
Here are the components of a GIS:
- Data Collection: This component is responsible for collecting geographic data from various sources such as maps, satellite imagery, and aerial photography.
- Data Storage: Once collected, the data must be stored in a database or a geodatabase. This component can be based on traditional database management systems or more specialised GIS databases.
- Data Management: This component includes tasks such as data quality control, data integration, and data maintenance. It is responsible for ensuring the accuracy and consistency of the data stored in the GIS.
- Data Analysis: This component allows users to analyze geographic data and make decisions based on the results of the analysis. Analysis functions include spatial query, map algebra, and spatial statistics.
- Map Display: This component is responsible for creating and displaying maps and visual representations of the data stored in the GIS. It includes tools for symbolising data, creating legends, and annotating maps.
- User Interface: This component provides an interface between the user and the GIS. It includes tools for data input, map display, and data analysis.
- GIS software: This component is the heart of the GIS. It integrates all the other components and provides a platform for creating and analyzing geographic information.
In summary, a GIS is a system that integrates data collection, storage, management, analysis, map display, user interface, and software to provide a complete solution for working with geographic information.
Here are the types of data used in GIS:
- Vector Data: This type of data represents geographical features as points, lines, and polygonal shapes. Vector data is used to represent discrete objects such as buildings, roads, and rivers.
- Raster Data: This type of data represents geographical features as a grid of cells, each of which has a value representing a specific attribute of the feature. Raster data is used to represent continuous surfaces such as terrain elevations, land use, and satellite imagery.
- Tabular Data: This type of data is stored in tables and is used to associate attribute information with geographic features. It is commonly used in GIS to store demographic data, land use information, and other descriptive information about geographic features.
- Metadata: This type of data provides information about the data, including its origin, accuracy, format, and the process used to create it. Metadata is essential for managing and understanding the data stored in a GIS.
- Remotely Sensed Data: This type of data is collected by remote sensing devices such as satellites and aerial photography. It includes imagery and elevation data.
- Crowdsourced Data: This type of data is collected from multiple sources and is typically collected by individuals using mobile devices or other technologies. Crowdsourced data can include photographs, geolocated information, and other types of data that can be used to update or supplement existing GIS data.
In summary, GIS data can be classified into various types including vector, raster, tabular, metadata, remotely sensed, and crowdsourced data. Each type of data has its own strengths and weaknesses, and different types of data are used in GIS to represent different aspects of the geography being studied.
Here are some of the common applications of GIS:
- Land Use Planning: GIS is used by city planners and urban designers to analyze and manage land use, such as zoning and development. It can help to identify areas for new development, predict the impact of new development on existing communities, and plan for transportation and infrastructure.
- Environmental Management: GIS is used to monitor and manage natural resources, such as forests, wetlands, and wildlife habitats. It can also be used to predict the impact of natural disasters such as floods, fires, and hurricanes.
- Emergency Response: GIS is used in emergency response management to identify potential hazards, predict the impact of emergencies, and coordinate responses to emergencies. It can also be used to monitor the spread of infectious diseases and respond to public health crises.
- Transportation Planning: GIS is used to plan and manage transportation systems, such as roads, bridges, and transit systems. It can help to identify potential traffic congestion, plan new routes, and optimize the use of existing transportation infrastructure.
- Retail and Marketing: GIS is used by retail businesses and marketing firms to analyze consumer behavior and target marketing efforts. It can be used to determine the most effective locations for retail outlets and to analyze consumer demographics and spending patterns.
- Healthcare: GIS is used to analyze and manage healthcare systems, including hospitals, clinics, and healthcare delivery systems. It can help to identify areas with the greatest need for healthcare services and to plan for the delivery of those services.
- Natural Resource Management: GIS is used to manage and analyze natural resources, such as water, minerals, and energy. It can help to identify areas with the greatest potential for resource extraction and to manage the extraction of those resources in an environmentally sustainable manner.
In summary, GIS has a wide range of applications, including land use planning, environmental management, emergency response, transportation planning, retail and marketing, healthcare, and natural resource management. These applications demonstrate the versatility and power of GIS in supporting decision-making and problem-solving across a variety of fields.
Here are the main components of GPS:
- Satellites: The GPS system consists of a network of satellites that orbit the Earth. These satellites transmit signals that can be used to determine the position, speed, and direction of a GPS receiver. There are currently 31 operational GPS satellites in orbit.
- Ground Control Stations: These stations are used to monitor the GPS satellites and to ensure that they are transmitting accurate signals. They also provide information to the satellites that is used to calculate their position and timing information.
- GPS Receivers: These are the devices that receive the signals from the GPS satellites and use them to calculate the position, speed, and direction of the receiver. GPS receivers can be integrated into a variety of devices, including smartphones, navigation systems, and military equipment.
- Antennas: GPS receivers have antennas that are used to receive the signals from the GPS satellites. The antennas can be integrated into the GPS receiver or can be external to the receiver.
- Software: GPS receivers typically have software that is used to process the signals from the GPS satellites and to calculate the position, speed, and direction of the receiver. Some GPS receivers also have additional software that provides additional features, such as navigation, mapping, and route planning.
In summary, GPS consists of satellites, ground control stations, GPS receivers, antennas, and software. These components work together to provide accurate positioning and timing information to users of GPS around the world.
GPS is a global navigation system that uses a network of satellites orbiting the Earth to provide positioning and timing information to users around the world. The basic working principle of GPS is triangulation. Here’s how it works:
- Signals from Satellites: Each GPS satellite transmits a signal that includes its position and the time the signal was sent. This information is received by GPS receivers on the ground.
- Determining Distance: The GPS receiver calculates the distance from the receiver to the GPS satellite by measuring the time it takes for the signal to travel from the satellite to the receiver. This is done by comparing the time the signal was sent (as recorded by the satellite) to the time the signal was received by the receiver.
- Triangulation: The GPS receiver uses the distances to at least three GPS satellites to determine its position. The receiver compares the distances to the known positions of the satellites to calculate its position on the Earth. This process is known as triangulation.
- Position Accuracy: The accuracy of the GPS receiver’s position is dependent on the number of satellites it can receive signals from, as well as the quality of the signals it receives. The more satellites the receiver can receive signals from, the more accurate the position information will be.
- Differential GPS: To further improve the accuracy of GPS, a technique called Differential GPS (DGPS) is used. DGPS uses ground-based reference stations to measure and correct for errors in the GPS signals. This results in much more accurate position information, often to within a few meters.
In summary, the working principle of GPS is based on triangulation, using signals from satellites, determining the distances to the satellites, and using triangulation to determine the position of the GPS receiver. The accuracy of the position information is improved by using differential GPS.
GPS is a widely used technology that has a wide range of applications in many different fields. Here are some of the most common applications of GPS:
- Navigation: GPS is used for navigation, both in vehicles and on foot. GPS receivers can be integrated into cars, trucks, boats, and aircraft, providing navigation information to drivers, pilots, and boat captains. Handheld GPS receivers are also used by hikers, cyclists, and other outdoor enthusiasts for navigation in the wilderness.
- Surveying and Mapping: GPS is used for surveying and mapping, providing accurate location information for mapping and geospatial analysis. This information is used for a wide range of purposes, including land-use planning, environmental analysis, and resource management.
- Agriculture: GPS is used in agriculture to improve crop yields, reduce waste, and minimize the use of inputs such as water, fertilisers, and pesticides. GPS-equipped tractors can be used to plant seeds, apply chemicals, and harvest crops, providing farmers with real-time information about the health of their crops.
- Military: GPS is widely used by the military for navigation, targeting, and positioning. GPS signals can be used to determine the position of enemy targets, providing critical information to military personnel in the field.
- Emergency Services: GPS is used by emergency services such as fire departments, police departments, and ambulance services to provide real-time information about the location of emergencies and the status of emergency personnel.
- Timing: GPS is used to provide accurate time information to a wide range of applications, including financial transactions, power grid management, and communication networks.
In summary, GPS has a wide range of applications in many different fields, including navigation, surveying and mapping, agriculture, military, emergency services, and timing. Its ability to provide accurate positioning and timing information makes it a valuable tool for a wide range of applications.