Basics of Remote Sensing & GIS | Date:20/12/2021

Basics of Remote Sensing & GIS 
Date:20/12/2021 
Paper solved by : Om Sonawane 

(c) Enlist the elements of visual image interpretation. Define the type of quality and quantity associated with respective elements.

Elements of visual image interpretation include:

1. Image quality: This refers to the overall quality of the image, including factors such as resolution, contrast, and noise. Quality in this context can be either quantitative (measured in terms of resolution, contrast, noise etc) or qualitative (based on the interpreter's perception of the image).

2. Image content: This refers to the features and objects within the image, such as roads, buildings, vegetation, and water bodies. The content can be either qualitative (based on the interpreter's perception of the features and objects) or quantitative (measured in terms of size, shape, location, etc)

3. Image context: This refers to the surroundings and environment of the features and objects within the image, such as the surrounding terrain, land use, and cultural features. The context can be both quantitative (measured in terms of land use, population density, etc) and qualitative (based on the interpreter's perception of the context)

4. Image association: This refers to the relationships and patterns between the features and objects within the image, such as the relationship between roads and buildings or the patterns of vegetation. The association can be both quantitative (measured in terms of distance, direction, etc) and qualitative (based on the interpreter's perception of the association)

5. Image inference: This refers to the process of drawing conclusions or making predictions from the features and objects within the image, such as inferring the land use or land cover from the vegetation patterns. The inference can be both quantitative (measured in terms of land use, land cover etc) and qualitative (based on the interpreter's perception of the inference)

It's important to note that image interpretation is a complex process and these elements are not mutually exclusive, they can overlap and interact with each other. The type of quality and quantity associated with each element will depend on the specific task and application of the interpretation, and the availability of data.

Q.3 

(A) What is the need of introducing filters in RS? Enlist the types of filters used in RS.

The need for filters in remote sensing (RS) is to enhance the image quality and to extract useful information from the image. Filters are used to suppress unwanted or irrelevant information in an image, such as noise, and to enhance the contrast of relevant features.

There are several types of filters that are commonly used in RS, including: 

1. Spatial filters: These filters operate on the spatial domain of an image and are used to enhance or suppress specific spatial frequencies or patterns within the image. Examples include median filters, which are used to remove noise, and edge-detection filters, which are used to enhance the edges of features within an image.

2. Spectral filters: These filters operate on the spectral domain of an image and are used to enhance or suppress specific spectral information within the image. Examples include band-pass filters, which are used to enhance specific wavelength ranges within an image, and vegetation indices, which are used to enhance the contrast between vegetation and other features within an image. 

3. Temporal filters: These filters operate on the temporal domain of an image and are used to enhance or suppress specific temporal information within the image. Examples include time-series filters, which are used to remove noise and clouds from time-series of images, and change detection filters, which are used to detect changes between images acquired at different times. 

4. Adaptive filters: These filters are designed to automatically adjust the filter parameters based on the characteristics of the image. Examples include the algorithm k-means clustering, which is used to classify pixels based on their spectral properties.

It's important to note that the choice of filter to use depends on the specific application and the characteristics of the image. In most cases, a combination of different filters is used to obtain the best results. 

(B) Explain scale of the photograph.

Scale in the context of photographs refers to the relationship between the size of an object in the photograph and the size of the same object in the real world. Scale can be expressed in a variety of ways, but it is typically expressed as a ratio or a representative fraction.

Representative Fraction (RF) is a ratio of the distance between two points on a photograph to the corresponding distance on the ground. For example, if an object is 100 meters long on the ground and it measures 2 centimeters on a photograph, the RF would be 1:50,000, meaning that 1 unit on the photograph represents 50,000 units on the ground.

Another way of expressing the scale is verbal scale, which is a description of the scale in words, such as "1 inch represents 1 mile"

It's important to note that the scale of a photograph is not constant across the entire image, but can vary depending on the altitude of the aircraft or satellite, the focal length of the camera lens and the distance of the object from the camera. Also the scale of the photograph can be affected by the ground resolution of the sensor which is the smallest feature that can be distinguished on the ground by the sensor.

Scale is an important concept in remote sensing and GIS, as it affects the accuracy and precision of the data, as well as the level of detail that can be seen in the image. 

(C) Enlist the Types of camera used in RS with its working principle and advantage? 

There are several types of cameras that are commonly used in remote sensing (RS), each with its own working principle and advantages:

Film Cameras: Film cameras use film to record the image, the film is sensitive to light, when exposed to light the light sensitive crystals on the film changes its structure and can be developed to produce an image. Film cameras are still used in some applications, such as aerial photography, but they have been largely replaced by digital cameras.

Charge-Coupled Device (CCD) Cameras: CCD cameras use a CCD sensor, which is a light-sensitive semiconductor device that converts light energy into electrical charges. The charges are then processed to produce an image. CCD cameras are widely used in RS, particularly in satellite-based remote sensing. Their advantage is that they have a high spatial resolution, high signal-to-noise ratio and are able to capture a wide range of wavelength bands. 

Complementary Metal-Oxide-Semiconductor (CMOS) Cameras: CMOS cameras use a CMOS sensor, which is a type of light-sensitive semiconductor device that converts light energy into electrical charges. The charges are then processed to produce an image. CMOS cameras are similar to CCD cameras in their working principle but have some advantages such as lower power consumption, and lower cost.

Pushbroom Cameras: Pushbroom cameras are used to capture multiple lines of an image at once, and they move along a direction to cover the whole image. They work by having a linear array detector (CCD or CMOS) that scans the scene and records the data as the platform moves. They are typically used in airborne and spaceborne imaging systems, and their advantage is that they have a high temporal resolution and can cover large areas in a single pass. 

Snapshot Cameras: Snapshot cameras are used to capture an image at a single moment in time, and they are mostly used for aerial and space-borne imaging systems. They work by having a single detector that captures the image at one instant. They have high spatial and spectral resolution, and can be used in a variety of applications such as hyperspectral imaging and stereo-photogrammetry.

It's important to note that the choice of camera to use depends on the specific application and the characteristics of the image that need to be captured. The technology of camera also continues to evolve and new types of cameras are being developed to meet the increasing demands of remote sensing. 

Q. 3

(a) What is film? Enlist the types of film used in RS?

Film is a light-sensitive material used to capture and record images. In traditional photography, film is made of a thin layer of emulsion, which is coated onto a plastic or paper base. The emulsion contains light-sensitive chemicals, such as silver halide crystals, that change their structure when exposed to light, allowing for the capture and recording of an image.

In remote sensing (RS), film is used in aerial photography, and it's a relatively old technology, but it still has some specific advantages and applications: 

Black and white film: This type of film is sensitive to all wavelengths of light, producing an image in shades of gray. It is typically used for applications that require high spatial resolution, such as mapping and surveying.

Color film: This type of film is sensitive to different wavelengths of light and produces an image in color. It is typically used for applications that require high color resolution, such as monitoring land use and land cover.

Infrared film: This type of film is sensitive to infrared wavelengths of light, and it produces an image that can be used to detect vegetation and other features that are invisible to the human eye. It is typically used for applications that require high spectral resolution, such as monitoring vegetation and detecting changes in land use.

Ultraviolet film: This type of film is sensitive to ultraviolet wavelengths of light, and it produces an image that can be used to detect features that are invisible to the human eye. It is typically used for applications such as atmospheric research and mineral exploration.

It's important to note that as technology evolved and digital cameras became more prevalent, the use of film in remote sensing has decreased, however, in some specific applications, film cameras still have advantages over digital cameras such as long-term archival and high resolution.

 

(B) Differentiate between low oblique aerial photograph and high oblique aerial photograph.

A low oblique aerial photograph is taken at a low angle, typically between 20 and 45 degrees, with the camera pointed slightly downward. This angle of view gives the photograph a more natural perspective and includes more of the ground and surrounding area in the frame.

A high oblique aerial photograph is taken at a much higher angle, typically greater than 45 degrees, with the camera pointed almost straight down. This angle of view provides a bird's-eye view of the area and emphasizes the vertical features of the landscape, such as buildings and structures. High oblique aerial photographs are often used for mapping and surveying purposes. 

(C) What is the concept of thermal Remote sensing?

Thermal remote sensing is the process of measuring the temperature of an object or surface from a distance, typically using a sensor mounted on an aircraft or satellite. The sensor detects the infrared radiation emitted by the object or surface, which is directly related to its temperature. This information can be used to create thermal images or maps that show the temperature distribution of the area being observed. 

Thermal remote sensing is used for a variety of applications, including monitoring the temperature of crops and forests, detecting and mapping hot springs and geysers, and identifying areas of heat loss in buildings. It is also commonly used in the fields of meteorology, geology, and environmental science. 

Thermal remote sensing technology is based on the fact that all objects emit thermal radiation. The amount of radiation emitted is dependent on the surface temperature of the object. The instruments used in thermal remote sensing are sensitive to the long-wave infrared radiation, which is emitted by all objects above absolute zero. The thermal remote sensing data is then used to create temperature maps, which can be used to detect, monitor and study various natural and human-made features of the earth surface. 

Q.4 

(A) Enlist the key components of GIS with their role. 

Data: The foundation of a GIS is the data it uses to represent geographic features and phenomena. This data can come in various forms, such as vector data (points, lines, and polygons), raster data (images and grids), and attribute data (descriptive information about the features).

Hardware: The physical components of a GIS include the computers, servers, and storage devices that are used to store and process data.

Software: GIS software is used to manage, analyze, and display geographic data. There are several types of GIS software available, including desktop, web, and mobile GIS. Some popular examples of GIS software include ArcGIS, QGIS, and Google Earth.

People: GIS is a tool that is used by people from different backgrounds and fields. The users of GIS include geographers, planners, engineers, ecologists, and many more.

Procedures: GIS also includes the procedures and processes used to create, manage, and analyze geographic data. These may include data capture, data processing, data analysis, and data dissemination.

Network: GIS also includes the communication infrastructure that allows data to be shared and analyzed. This infrastructure can include wired or wireless networks, as well as cloud-based services.

Standards: GIS data is often shared and used across different organizations and platforms, so it's important to use standards for data formats, data quality, data accuracy and data integration.

(B) What are the requirements of ground Truth data in remote sensing data analysis?

Ground truth data refers to information collected on the ground, such as measurements, observations, or samples, that is used to validate or calibrate remote sensing data. The requirements for ground truth data in remote sensing data analysis include: 

Relevance: The ground truth data should be relevant to the remote sensing data and the research question being addressed. This means that the ground truth data should be collected at the same time and in the same location as the remote sensing data. 

Quality: The ground truth data should be of high quality, meaning that it should be accurate, precise, and unbiased. This can be achieved through proper measurement techniques and protocols, as well as quality control procedures.

Quantity: The amount of ground truth data required will depend on the research question and the remote sensing data being analyzed. In general, a larger sample size will provide more reliable results. 

Validation: The ground truth data should be used to validate the remote sensing data, meaning that it should be used to check the accuracy and reliability of the remote sensing data. This can be done by comparing the two sets of data and looking for patterns and discrepancies.

Completeness: The ground truth data should be complete, meaning that it should cover all the areas and features of interest in the remote sensing data. This can be achieved through a well-planned sampling strategy.

Representativeness: The ground truth data should be representative of the larger population of interest, meaning that it should be collected from a representative sample of the area being studied. This can be achieved through random sampling or stratified sampling. 

(C) Explain the working principle of GPS?

The Global Positioning System (GPS) is a satellite-based navigation system that uses a network of satellites, ground control stations, and GPS receivers to determine the location, velocity, and time of a GPS receiver on the earth. The working principle of GPS is based on the use of trilateration, which is a method of determining the position of a point by measuring the distance to it from known points at two or more locations.

The GPS system consists of three segments: the space segment, the control segment, and the user segment.

The Space Segment: This segment includes a network of satellites in orbit around the earth. These satellites transmit radio signals that contain information about their location and the time the signal was transmitted. 

The Control Segment: This segment includes a network of ground control stations that are used to track the satellites, monitor their performance, and make any necessary adjustments to their orbits.

The User Segment: This segment includes the GPS receivers that are used by individuals and organizations to determine their location, velocity, and time.

When a GPS receiver is turned on, it searches for and receives signals from multiple GPS satellites. The receiver uses the signals from at least four satellites to determine the user's location by trilateration. The receiver uses the time that each signal was transmitted and the distance between the receiver and each satellite to calculate the user's position. The distance between the receiver and each satellite is determined by the time it takes for the signal to travel from the satellite to the receiver.

The receiver can then use this information to calculate the user's position, velocity and time. This information can be used for a variety of applications, such as navigation, mapping, and surveying.

It's worth noting that GPS isn't the only satellite based positioning system, other systems such as GLONASS (Russian), Galileo (European), BeiDou (Chinese) and NavIC (Indian) also exist, but GPS is the most widely used and available. 

Q.4 ( OR ) 

(A) Enlist instruments used for ground truthing.

Ground truthing is the process of collecting and verifying data on the ground to validate or calibrate remote sensing data. The instruments used for ground truthing can vary depending on the specific application and research question, but some common instruments include : 

Total Station: A total station is a surveying instrument that combines a theodolite (an instrument for measuring angles in the horizontal and vertical planes) and an electronic distance meter (EDM) to measure both angles and distances to a target. Total stations can be used to collect precise location and elevation information for ground control points and other features. 

Handheld GPS Receiver: A handheld GPS receiver is a portable device that can be used to determine the location of a point on the ground using satellite signals. Handheld GPS receivers can be used to collect location information for ground control points, sampling locations, and other features.

Spectroradiometer: A spectroradiometer is an instrument that can be used to measure the reflectance or radiance of a surface in different parts of the electromagnetic spectrum. Spectroradiometers can be used to collect ground truth data for the validation of remotely sensed data, such as satellite imagery.

Soil Sampler: Soil samplers are used for taking soil samples for laboratory analysis. They can be used to collect information about soil properties such as texture, pH, organic matter content, and nutrient levels.

Camera: A camera can be used to take photographs of the ground or other features. These photographs can be used to create visual records of the ground truth data and also to verify the accuracy of remotely sensed data.

Field Notebook: A field notebook is used to record observations, measurements, and other data collected during the ground truthing process. It is an important tool for recording information and keeping track of the data collected.

Anemometer: An anemometer is an instrument used to measure wind speed and direction. This instrument can be useful in many environmental studies, such as atmospheric and wind energy studies.

Weather Station: A weather station is an instrument that can measure temperature, humidity, precipitation, solar radiation, and other meteorological parameters. This information can be used to validate atmospheric correction and energy balance models.

These are just a few examples of the types of instruments that can be used for ground truthing. The specific instruments used will depend on the research question, the type of remote sensing data being collected, and the environment in which the data is being collected.

(B)  What are almanac and ephemeris data?

Almanac and ephemeris data are types of information that are used by GPS receivers to determine the location of a point on the earth. 

Almanac data: Almanac data is a set of information that is transmitted by the GPS satellites and contains general information about the GPS satellite system, such as the satellite orbits, the time of transmission, and the health of the satellite. Almanac data is used by the GPS receiver to quickly acquire a rough position and determine which satellites are in view. 

Ephemeris data: Ephemeris data is a set of information that is transmitted by the GPS satellites and contains detailed information about the current orbital position of the satellite. This information is used by the GPS receiver to calculate the exact location of the satellite at any given time. This is the data that the GPS receiver uses to calculate the distance between the satellite and the receiver. 

Both the Almanac and ephemeris data are sent as part of the signal from the GPS satellites, and the GPS receiver uses this data to calculate the distance between the receiver and the satellite. Once the distance between the receiver and the satellite is known, the receiver can calculate the location of the receiver using a technique called trilateration. The receiver uses the distance information and the known location of the satellite to determine the location of the receiver on the earth. 

Almanac data is valid for a longer period of time, whereas ephemeris data is valid for a shorter period of time and needs to be updated more frequently. However, the almanac data alone is not enough for an accurate position calculation, and the ephemeris data is needed for a more precise location calculation. 

(C) Highlight the role of remote sensing in environmental impact assessment. 

Remote sensing plays an important role in environmental impact assessments by providing information about the current state of an area and monitoring changes over time. This information can be used to identify and evaluate the potential impacts of a proposed project or development, such as changes in land use, vegetation, and water resources. Remote sensing data can also be used to track the progress of mitigation and restoration efforts.

This technology can be used to detect and map natural resources, such as forests, wetlands, and minerals, as well as anthropogenic features, such as infrastructure, roads, and urban areas. It can also be used to monitor the health of ecosystems, such as wetlands, forests, and coral reefs, and to detect and map invasive species, pollution and natural hazards. Overall, remote sensing can provide valuable information for decision-making in the context of environmental impact assessment. 

Q.5 

(A) Enlist the Application of remote sensing in Hydrology. 

There are several applications of remote sensing in hydrology, including:

Watershed Delineation: Remote sensing data can be used to identify the boundary of a watershed and to create digital elevation models (DEMs) that can be used to calculate flow direction and volume.

Flood Mapping: Remote sensing data can be used to detect and map flooded areas, providing information on the extent and severity of flooding. 

Measuring and monitoring water levels, flow, and quality in rivers and lakes.

Detecting and mapping surface water bodies, wetlands, and groundwater resources.

Assessing soil moisture, vegetation health, and evapotranspiration rates.

Identifying and mapping flood-prone areas and monitoring flood events.

Studying the impacts of land use and land cover change on water resources.

Monitoring and forecasting droughts and water scarcity.

Assessing the impacts of climate change on water resources. 

(B) Explain are the functions of GIS? 

GIS (Geographic Information Systems) is a technology used for capturing, storing, manipulating, analyzing, managing, and displaying all forms of geographically referenced information. GIS functions include:

Data capture: GIS allows for the capture of geographic data from various sources such as satellite imagery, aerial photography, and field surveys. 

Data management: GIS allows for the storage and management of large amounts of geographic data in a centralized database, making it easily accessible and searchable.

Data analysis: GIS provides tools for analyzing and manipulating geographic data, such as spatial querying, overlay analysis, and network analysis. 

Data visualization: GIS provides tools for creating maps and other visual representations of geographic data, such as 3D models and animations.

Data sharing: GIS allows for the sharing of geographic data through web-based services and other platforms, making it accessible to a wide range of users.

Spatial decision making: GIS provides a platform for decision making by providing spatial analysis, data visualization and data management. 

Mobile GIS: GIS data and analysis can be accessed by mobile devices, allowing for field data collection and spatial analysis in real-time.

Remote Sensing: GIS software can be used to process and analyze remote sensing data for different applications.

 

(C) Justify “GIS is an information infrastructure”.

GIS is considered an information infrastructure because it provides a framework for the collection, storage, management, analysis, and dissemination of geographically-referenced information. This framework is built on a range of technologies and concepts, such as spatial data models, geographic data formats, and spatial analysis algorithms, that work together to enable the efficient and effective use of geographic information.

In the same way that traditional infrastructure, such as roads and bridges, provides the physical infrastructure for transportation, GIS provides the information infrastructure for geographic information. GIS allows organizations to store and manage large amounts of geographic data in a centralized database, making it easily accessible and searchable. It also provides tools for analyzing and manipulating geographic data, such as spatial querying, overlay analysis, and network analysis, which can be used to support decision making and planning.

Furthermore, GIS provides the ability to visualize geographic data in the form of maps and other visual representations, making it easy for a wide range of users to understand and interpret the information. Additionally, GIS allows for the sharing of geographic data through web-based services and other platforms, making it accessible to a wide range of users and organizations.

All these capabilities and tools make GIS a powerful and essential information infrastructure for the management, analysis and dissemination of geographic information, which is critical for a wide range of applications in fields such as urban planning, natural resources management, emergency response, and many more. 

Q.5 

(A) Explain the concept of thermal image interpretation.

Thermal image interpretation is the process of analyzing and interpreting thermal images to extract useful information about the features and properties of the scene being imaged. Thermal images are produced by sensors that detect infrared radiation emitted by objects and surfaces, which can be used to infer their temperature and other characteristics.

The process of thermal image interpretation typically involves several steps:

Image acquisition: The thermal image is captured by a sensor, typically mounted on an aircraft or satellite, and then processed to remove noise and improve image quality.

Image registration: The thermal image is registered with other data sources, such as optical imagery or digital elevation models, to provide context and improve accuracy. 

Image interpretation: The thermal image is analyzed to extract information about the features and properties of the scene. This may involve identifying specific objects or features, such as buildings, roads, or bodies of water, or measuring temperature and other physical properties.

Image analysis: The information extracted from the thermal image is further analyzed to identify patterns, trends, and relationships, such as changes in temperature over time or the distribution of temperature across different parts of the scene.

Image presentation: The results of the thermal image interpretation are presented in a clear and understandable format, such as maps, graphs, or reports, to support decision-making and planning.

Thermal image interpretation can be applied in many fields such as meteorology, geology, agriculture, and environmental management, among others. In meteorology, thermal images can be used to track and forecast severe weather events, such as hurricanes and tornadoes.

In geology, thermal images can be used to identify hot springs, geysers, and other thermal features. In agriculture, thermal images can be used to monitor crop health and identify irrigation problems. In environmental management, thermal images can be used to monitor the health of ecosystems, track the spread of invasive species, and identify areas of land degradation.

(b) What are the limitations of GIS?

GIS (Geographic Information Systems) is a powerful tool for capturing, storing, analyzing, and visualizing geographic information, however it also has some limitations:

Data availability: GIS relies on the availability of accurate and up-to-date geographic data, which can be difficult and expensive to acquire, especially in developing countries or remote areas.

Data quality: GIS relies on the quality of the data, and errors or inaccuracies in the data can lead to incorrect or misleading results.

Data compatibility: GIS data can come from a variety of sources, and may not be compatible with each other, leading to difficulties in integration and analysis.

Data scalability: GIS can handle large amounts of data, but the performance of GIS software can be affected when dealing with very large datasets, or when trying to process large numbers of concurrent users.

Spatial complexity: GIS is designed to handle spatial data and the complexity of spatial relationships, but dealing with the complexity of large and complex datasets can be difficult for GIS users.

Limited to a two-dimensional representation: GIS is designed to handle two-dimensional data, but in some cases, 3D modeling and representation is required, therefore GIS have limitations in handling 3D data.

Limited analytical capabilities: GIS is good at spatial analysis but it lacks advanced statistical analysis tools.

Limited ability to handle real-time data: GIS software is not designed to handle real-time data, that is data that is updated frequently and needs to be visualized in near real-time.

Limited ability to handle uncertainty and errors: GIS software is not designed to handle uncertainty and errors in data, which can lead to incorrect or misleading results.

Despite these limitations, GIS remains a widely used and powerful tool for managing, analyzing and visualizing geographic information. Advances in technology and the growing availability of geographic data are helping to overcome some of these limitations and make GIS an even more powerful tool for decision making and planning. 

(C) Enlist the Application of remote sensing in ocean and coastal monitoring. 

Remote sensing has a wide range of applications in ocean and coastal monitoring, including:

Mapping and monitoring of ocean and coastal environments: Remote sensing is used to map and monitor the physical and biological characteristics of the ocean and coastal environments, such as sea surface temperature, chlorophyll concentration, and sea ice cover.

Monitoring of ocean currents and circulation: Remote sensing is used to measure ocean currents, waves, and circulation patterns, which are important for understanding ocean circulation and the movement of heat, salt, and other ocean properties.

Monitoring of ocean and coastal pollution: Remote sensing is used to detect and map sources of pollution, such as oil spills, algal blooms, and plastic debris, as well as to monitor their impacts on the ocean and coastal environment.

Monitoring of coastal erosion and land use change: Remote sensing is used to detect and map coastal erosion and land use change, such as urbanization, agriculture, and deforestation, which can have significant impacts on coastal ecosystems.

Monitoring of marine biodiversity and fisheries: Remote sensing is used to map and monitor the distribution and abundance of marine species, such as fish, marine mammals, and seabirds, and to assess their populations and habitats.

Mapping and monitoring of ocean and coastal hazards: Remote sensing is used to map and monitor ocean and coastal hazards, such as hurricanes, tsunamis, and storm surges, which can have significant impacts on coastal communities and infrastructure.

Mapping and monitoring of ocean and coastal resources: Remote sensing is used to map and monitor ocean and coastal resources, such as oil and gas reserves, mineral resources, and marine protected areas, which are important for sustainable management and conservation.

Climate change monitoring: Remote sensing is used to monitor the impacts of climate change on the ocean and coastal environments, such as sea-level rise, ocean acidification and temperature changes.

All these applications of remote sensing in ocean and coastal monitoring help to provide a comprehensive understanding of the ocean and coastal environments, and support sustainable management and conservation of marine resources.