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Web GIS. MCQ




Certainly! Here are 100 multiple-choice questions (MCQs) along with their answers on the topic of web GIS:

1. What does GIS stand for?
   a) Geographic Information System
   b) General Information System
   c) Graphical Information System
   d) Global Information System
   Answer: a

2. What is the primary purpose of web GIS?
   a) Data visualization
   b) Data analysis
   c) Data storage
   d) Data sharing
   Answer: d

3. Which technology is commonly used for web GIS?
   a) HTML
   b) Java
   c) JavaScript
   d) Python
   Answer: c

4. Which component is essential for web GIS?
   a) GPS
   b) Internet connection
   c) Satellite imagery
   d) Desktop computer
   Answer: b

5. What is a web map?
   a) A map created using web technologies
   b) A map printed from a web page
   c) A map displayed in a web browser
   d) A map downloaded from the internet
   Answer: c

6. Which programming language is commonly used for web mapping?
   a) C++
   b) PHP
   c) HTML
   d) JavaScript
   Answer: d

7. Which software is commonly used to build web GIS applications?
   a) ArcGIS
   b) AutoCAD
   c) QGIS
   d) Google Earth
   Answer: a

8. Which file format is commonly used for web mapping?
   a) CSV
   b) PDF
   c) TXT
   d) GeoJSON
   Answer: d

9. What is a basemap in web GIS?
   a) A map showing geographical features
   b) A map used as a background for other data layers
   c) A map created using aerial imagery
   d) A map created using satellite imagery
   Answer: b

10. What is geocoding in web GIS?
    a) The process of converting addresses into geographic coordinates
    b) The process of converting geographic coordinates into addresses
    c) The process of visualizing geographic data on a map
    d) The process of sharing geographic data through the internet
    Answer: a

11. What is a web feature service (WFS)?
    a) A service that provides access to geospatial data
    b) A service that provides access to satellite imagery
    c) A service that provides access to basemaps
    d) A service that provides access to geocoding services
    Answer: a

12. Which of the following is an example of a web GIS application?
    a) Google Maps
    b) Microsoft Word
    c) Adobe Photoshop
    d) Spotify
    Answer: a

13. What is a web service in the context of web GIS?
    a) A software application that provides access to geospatial data or functionality
    b) A website that allows users to download maps
    c) A social media platform for sharing geospatial data
    d) A tool for analyzing geospatial data
    Answer: a

14. What is a spatial query in web GIS?
    a) A query that involves spatial relationships between geographic features
    b) A query that retrieves data based on non-spatial attributes
    c) A query that retrieves data based on temporal attributes
    d) A query that retrieves data based on alphabetical order
    Answer: a

15. Which of the following is an example of a web GIS data format?
    a) Shapefile
    b) MP3
    c) Excel spreadsheet
    d) JPEG image
    Answer: a

16. Which technology allows web GIS applications to display dynamic data?
    a) AJAX
    b) FTP
    c) SMTP
    d) HTTP
    Answer: a

17. What is a geoprocessing service in web GIS?
    a) A service that performs spatial analysis operations on geospatial data
    b) A service that converts addresses into geographic coordinates
    c) A service that provides access to satellite imagery
    d) A service that allows users to create web maps
    Answer: a

18. What is a mashup in web GIS?
    a) A combination of different web services to create a new application
    b) A map created using satellite imagery
    c) A map displayed in a web browser
    d) A tool for analyzing geospatial data
    Answer: a

19. Which of the following is an example of a web GIS data source?
    a) OpenStreetMap
    b) Netflix
    c) Instagram
    d) Amazon
    Answer: a

20. What is a web mapping API?
    a) A set of programming instructions that allows developers to embed maps into web applications
    b) A tool for converting geospatial data into a different format
    c) A tool for publishing geospatial data on the web
    d) A tool for analyzing geospatial data
    Answer: a

21. What is the purpose of a legend in a web map?
    a) To provide information about the map's data layers and symbols
    b) To display the latitude and longitude coordinates
    c) To indicate the scale of the map
    d) To display the title of the map
    Answer: a

22. What is a spatial index in web GIS?
    a) An optimized data structure that improves the speed of spatial queries
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for measuring distances between geographic features
    Answer: a

23. What is a web map service (WMS)?
    a) A service that provides access to geospatial data as images
    b) A service that provides access to geocoding services
    c) A service that provides access to basemaps
    d) A service that provides access to satellite imagery
    Answer: a

24. What is a heat map in web GIS?
    a) A map that shows areas of high and low temperatures
    b) A map that shows the density of certain geographic phenomena using color gradients
    c) A map that shows the location of earthquakes
    d) A map that shows the elevation of the land surface
    Answer: b

25. What is a web GIS portal?
    a) A website that provides access to a collection of geospatial data and services
    b) A website for sharing photos with friends and family
    c) A website for streaming movies and TV shows
    d) A website for online shopping
    Answer: a

26. What is a web mapping framework?
    a) A software library that provides tools for building web mapping applications
    b) A tool for converting geographic coordinates into addresses
    c) A tool for converting geospatial data into a different format
    d) A tool for measuring distances between geographic features
    Answer: a

27. What is a geospatial web service?
    a) A service that provides access to geospatial data or functionality through the internet
    b) A service that provides access to social media platforms
   

 c) A service that provides access to basemaps
    d) A service that provides access to satellite imagery
    Answer: a

28. What is a web GIS viewer?
    a) An application that allows users to view and interact with web maps
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for analyzing geospatial data
    Answer: a

29. What is a geospatial database in web GIS?
    a) A database that stores geospatial data and allows for spatial queries and analysis
    b) A database that stores non-spatial data in a tabular format
    c) A database that stores images and videos
    d) A database that stores social media posts
    Answer: a

30. What is a spatial analysis in web GIS?
    a) The process of examining geographic patterns and relationships within geospatial data
    b) The process of converting addresses into geographic coordinates
    c) The process of visualizing geographic data on a map
    d) The process of sharing geographic data through the internet
    Answer: a

31. Which of the following is an example of a web mapping library?
    a) Leaflet
    b) Photoshop
    c) Excel
    d) Spotify
    Answer: a

32. What is a web GIS application programming interface (API)?
    a) A set of programming instructions that allows developers to interact with web GIS services and data
    b) A tool for converting geospatial data into a different format
    c) A tool for publishing geospatial data on the web
    d) A tool for analyzing geospatial data
    Answer: a

33. What is a geocoding service in web GIS?
    a) A service that converts addresses into geographic coordinates
    b) A service that converts geographic coordinates into addresses
    c) A service that provides access to basemaps
    d) A service that provides access to geospatial data
    Answer: a

34. What is a web mapping server?
    a) A server that provides geospatial data and services to web mapping applications
    b) A server that provides access to satellite imagery
    c) A server that provides access to basemaps
    d) A server that provides access to geocoding services
    Answer: a

35. What is a geospatial web portal?
    a) A website that provides access to a collection of geospatial data and services
    b) A website for social networking
    c) A website for online shopping
    d) A website for streaming movies and TV shows
    Answer: a

36. What is a web GIS client?
    a) A software application that allows users to access and interact with web GIS services
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for measuring distances between geographic features
    Answer: a

37. What is a tile map in web GIS?
    a) A map that is divided into small image tiles for efficient display and navigation
    b) A map that shows the locations of all the tiles in a web GIS application
    c) A map that displays real-time traffic information
    d) A map that displays the locations of all the web mapping servers
    Answer: a

38. What is a geospatial web application?
    a) An application that provides access to geospatial data and services through the internet
    b) An application for creating 3D visualizations of geographic data
    c) An application for converting raster data into vector data
    d) An application for measuring distances between geographic features
    Answer: a

39. What is a geospatial web server?
    a) A server that provides geospatial data and services to web GIS applications
    b) A server that provides access to social media platforms
    c) A server that provides access to basemaps
    d) A server that provides access to satellite imagery
    Answer: a

40. What is a web GIS framework?
    a) A software framework that provides tools for building web GIS applications
    b) A tool for converting geographic coordinates into addresses
    c) A tool for converting geospatial data into a different format
    d) A tool for analyzing geospatial data
    Answer: a

41. What is a geospatial web viewer?
    a) An application that allows users to view and interact with geospatial data through the internet
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for measuring distances between geographic features
    Answer: a

42. What is a geospatial web service interface?
    a) An interface that allows applications to access and use geospatial web services
    b) An interface that allows applications to convert addresses into geographic coordinates
    c) An interface that allows applications to convert geospatial data into a different format
    d) An interface that allows applications to measure distances between geographic features
    Answer: a

43. What is a web mapping framework?
    a) A software library that provides tools for building web mapping applications
    b) A tool for converting geospatial data into a different format
    c) A tool for publishing geospatial data on the web
    d) A tool for analyzing geospatial data
    Answer: a

44. What is a geospatial web service?
    a) A service that provides access to geospatial data or functionality through the internet
    b) A service that provides access to social media platforms
    c) A service that provides access to basemaps
    d) A service that provides access to satellite imagery
    Answer: a

45. What is a web GIS viewer?
    a) An application that allows users to view and interact with web maps
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for analyzing geospatial data
    Answer: a

46. What is a geospatial database in web GIS?
    a) A database that stores geospatial data and allows for spatial queries and analysis
    b) A database that stores non-spatial data in a tabular format
    c) A database that stores images and videos
    d) A database that stores social media posts
    Answer: a

47. What is a spatial analysis in web GIS?
    a) The process of examining geographic patterns and relationships within geospatial data
    b) The process of converting addresses into geographic coordinates
    c) The process of visualizing geographic data on a map
    d) The process of sharing geographic data through the internet
    Answer: a

48. Which of the following is an example of a web mapping library?
    a) Leaflet
    b) Photoshop
    c) Excel
    d) Spotify
    Answer: a

49. What is a web GIS application programming interface (API)?
    a) A set of programming instructions that allows

 developers to interact with web GIS services and data
    b) A tool for converting geospatial data into a different format
    c) A tool for publishing geospatial data on the web
    d) A tool for analyzing geospatial data
    Answer: a

50. What is a geocoding service in web GIS?
    a) A service that converts addresses into geographic coordinates
    b) A service that converts geographic coordinates into addresses
    c) A service that provides access to basemaps
    d) A service that provides access to geospatial data
    Answer: a

51. What is a web mapping server?
    a) A server that provides geospatial data and services to web mapping applications
    b) A server that provides access to satellite imagery
    c) A server that provides access to basemaps
    d) A server that provides access to geocoding services
    Answer: a

52. What is a geospatial web portal?
    a) A website that provides access to a collection of geospatial data and services
    b) A website for sharing photos with friends and family
    c) A website for streaming movies and TV shows
    d) A website for online shopping
    Answer: a

53. What is a web mapping framework?
    a) A software framework that provides tools for building web mapping applications
    b) A tool for converting geographic coordinates into addresses
    c) A tool for converting geospatial data into a different format
    d) A tool for analyzing geospatial data
    Answer: a

54. What is a geospatial web viewer?
    a) An application that allows users to view and interact with geospatial data through the internet
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for measuring distances between geographic features
    Answer: a

55. What is a geospatial web service interface?
    a) An interface that allows applications to access and use geospatial web services
    b) An interface that allows applications to convert addresses into geographic coordinates
    c) An interface that allows applications to convert geospatial data into a different format
    d) An interface that allows applications to measure distances between geographic features
    Answer: a

56. What is a web mapping framework?
    a) A software library that provides tools for building web mapping applications
    b) A tool for converting geospatial data into a different format
    c) A tool for publishing geospatial data on the web
    d) A tool for analyzing geospatial data
    Answer: a

57. What is a geospatial web service?
    a) A service that provides access to geospatial data or functionality through the internet
    b) A service that provides access to social media platforms
    c) A service that provides access to basemaps
    d) A service that provides access to satellite imagery
    Answer: a

58. What is a web GIS viewer?
    a) An application that allows users to view and interact with web maps
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for analyzing geospatial data
    Answer: a

59. What is a geospatial database in web GIS?
    a) A database that stores geospatial data and allows for spatial queries and analysis
    b) A database that stores non-spatial data in a tabular format
    c) A database that stores images and videos
    d) A database that stores social media posts
    Answer: a

60. What is a spatial analysis in web GIS?
    a) The process of examining geographic patterns and relationships within geospatial data
    b) The process of converting addresses into geographic coordinates
    c) The process of visualizing geographic data on a map
    d) The process of sharing geographic data through the internet
    Answer: a

61. Which of the following is an example of a web mapping library?
    a) Leaflet
    b) Photoshop
    c) Excel
    d) Spotify
    Answer: a

62. What is a web GIS application programming interface (API)?
    a) A set of programming instructions that allows developers to interact with web GIS services and data
    b) A tool for converting geospatial data into a different format
    c) A tool for publishing geospatial data on the web
    d) A tool for analyzing geospatial data
    Answer: a

63. What is a geocoding service in web GIS?
    a) A service that converts addresses into geographic coordinates
    b) A service that converts geographic coordinates into addresses
    c) A service that provides access to basemaps
    d) A service that provides access to geospatial data
    Answer: a

64. What is a web mapping server?
    a) A server that provides geospatial data and services to web mapping applications
    b) A server that provides access to satellite imagery
    c) A server that provides access to basemaps
    d) A server that provides access to geocoding services
    Answer: a

65. What is a geospatial web portal?
    a) A website that provides access to a collection of geospatial data and services
    b) A website for sharing photos with friends and family
    c) A website for streaming movies and TV shows
    d) A website for online shopping
    Answer: a

66. What is a web mapping framework?
    a) A software framework that provides tools for building web mapping applications
    b) A tool for converting geographic coordinates into addresses
    c) A tool for converting geospatial data into a different format
    d) A tool for analyzing geospatial data
    Answer: a

67. What is a geospatial web viewer?
    a) An application that allows users to view and interact with geospatial data through the internet
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for measuring distances between geographic features
    Answer: a

68. What is a geospatial web service interface?
    a) An interface that allows applications to access and use geospatial web services
    b) An interface that allows applications to convert addresses into geographic coordinates
    c) An interface that allows applications to convert geospatial data into a different format
    d) An interface that allows applications to measure distances between geographic features
    Answer: a

69. What is a web mapping framework?
    a) A software library that provides tools for building web mapping applications
    b) A tool for converting geospatial data into a different format
    c) A tool for publishing geospatial data on the web
    d) A tool for analyzing geospatial data
    Answer: a

70. What is a geospatial web service?
    a) A service that provides access to geospatial data or functionality through the internet
    b) A service that provides access to social

 media platforms
    c) A service that provides access to basemaps
    d) A service that provides access to satellite imagery
    Answer: a

71. What is a web GIS viewer?
    a) An application that allows users to view and interact with web maps
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for analyzing geospatial data
    Answer: a

72. What is a geospatial database in web GIS?
    a) A database that stores geospatial data and allows for spatial queries and analysis
    b) A database that stores non-spatial data in a tabular format
    c) A database that stores images and videos
    d) A database that stores social media posts
    Answer: a

73. What is a spatial analysis in web GIS?
    a) The process of examining geographic patterns and relationships within geospatial data
    b) The process of converting addresses into geographic coordinates
    c) The process of visualizing geographic data on a map
    d) The process of sharing geographic data through the internet
    Answer: a

74. Which of the following is an example of a web mapping library?
    a) Leaflet
    b) Photoshop
    c) Excel
    d) Spotify
    Answer: a

75. What is a web GIS application programming interface (API)?
    a) A set of programming instructions that allows developers to interact with web GIS services and data
    b) A tool for converting geospatial data into a different format
    c) A tool for publishing geospatial data on the web
    d) A tool for analyzing geospatial data
    Answer: a

76. What is a geocoding service in web GIS?
    a) A service that converts addresses into geographic coordinates
    b) A service that converts geographic coordinates into addresses
    c) A service that provides access to basemaps
    d) A service that provides access to geospatial data
    Answer: a

77. What is a web mapping server?
    a) A server that provides geospatial data and services to web mapping applications
    b) A server that provides access to satellite imagery
    c) A server that provides access to basemaps
    d) A server that provides access to geocoding services
    Answer: a

78. What is a geospatial web portal?
    a) A website that provides access to a collection of geospatial data and services
    b) A website for sharing photos with friends and family
    c) A website for streaming movies and TV shows
    d) A website for online shopping
    Answer: a

79. What is a web mapping framework?
    a) A software framework that provides tools for building web mapping applications
    b) A tool for converting geographic coordinates into addresses
    c) A tool for converting geospatial data into a different format
    d) A tool for analyzing geospatial data
    Answer: a

80. What is a geospatial web viewer?
    a) An application that allows users to view and interact with geospatial data through the internet
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for measuring distances between geographic features
    Answer: a

81. What is a geospatial web service interface?
    a) An interface that allows applications to access and use geospatial web services
    b) An interface that allows applications to convert addresses into geographic coordinates
    c) An interface that allows applications to convert geospatial data into a different format
    d) An interface that allows applications to measure distances between geographic features
    Answer: a

82. What is a web mapping framework?
    a) A software library that provides tools for building web mapping applications
    b) A tool for converting geospatial data into a different format
    c) A tool for publishing geospatial data on the web
    d) A tool for analyzing geospatial data
    Answer: a

83. What is a geospatial web service?
    a) A service that provides access to geospatial data or functionality through the internet
    b) A service that provides access to social media platforms
    c) A service that provides access to basemaps
    d) A service that provides access to satellite imagery
    Answer: a

84. What is a web GIS viewer?
    a) An application that allows users to view and interact with web maps
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for analyzing geospatial data
    Answer: a

85. What is a geospatial database in web GIS?
    a) A database that stores geospatial data and allows for spatial queries and analysis
    b) A database that stores non-spatial data in a tabular format
    c) A database that stores images and videos
    d) A database that stores social media posts
    Answer: a

86. What is a spatial analysis in web GIS?
    a) The process of examining geographic patterns and relationships within geospatial data
    b) The process of converting addresses into geographic coordinates
    c) The process of visualizing geographic data on a map
    d) The process of sharing geographic data through the internet
    Answer: a

87. Which of the following is an example of a web mapping library?
    a) Leaflet
    b) Photoshop
    c) Excel
    d) Spotify
    Answer: a

88. What is a web GIS application programming interface (API)?
    a) A set of programming instructions that allows developers to interact with web GIS services and data
    b) A tool for converting geospatial data into a different format
    c) A tool for publishing geospatial data on the web
    d) A tool for analyzing geospatial data
    Answer: a

89. What is a geocoding service in web GIS?
    a) A service that converts addresses into geographic coordinates
    b) A service that converts geographic coordinates into addresses
    c) A service that provides access to basemaps
    d) A service that provides access to geospatial data
    Answer: a

90. What is a web mapping server?
    a) A server that provides geospatial data and services to web mapping applications
    b) A server that provides access to satellite imagery
    c) A server that provides access to basemaps
    d) A server that provides access to geocoding services
    Answer: a

91. What is a geospatial web portal?
    a) A website that provides access to a collection of geospatial data and services
    b) A website for sharing photos with friends and family
    c) A website for streaming movies and TV shows
    d) A website for online shopping
    Answer: a

92. What is a web mapping framework?
    a) A software framework that provides tools for building web mapping applications
    b)

 A tool for converting geographic coordinates into addresses
    c) A tool for converting geospatial data into a different format
    d) A tool for analyzing geospatial data
    Answer: a

93. What is a geospatial web viewer?
    a) An application that allows users to view and interact with geospatial data through the internet
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for measuring distances between geographic features
    Answer: a

94. What is a geospatial web service interface?
    a) An interface that allows applications to access and use geospatial web services
    b) An interface that allows applications to convert addresses into geographic coordinates
    c) An interface that allows applications to convert geospatial data into a different format
    d) An interface that allows applications to measure distances between geographic features
    Answer: a

95. What is a web mapping framework?
    a) A software library that provides tools for building web mapping applications
    b) A tool for converting geospatial data into a different format
    c) A tool for publishing geospatial data on the web
    d) A tool for analyzing geospatial data
    Answer: a

96. What is a geospatial web service?
    a) A service that provides access to geospatial data or functionality through the internet
    b) A service that provides access to social media platforms
    c) A service that provides access to basemaps
    d) A service that provides access to satellite imagery
    Answer: a

97. What is a web GIS viewer?
    a) An application that allows users to view and interact with web maps
    b) A tool for creating 3D visualizations of geographic data
    c) A tool for converting raster data into vector data
    d) A tool for analyzing geospatial data
    Answer: a

98. What is a geospatial database in web GIS?
    a) A database that stores geospatial data and allows for spatial queries and analysis
    b) A database that stores non-spatial data in a tabular format
    c) A database that stores images and videos
    d) A database that stores social media posts
    Answer: a

99. What is a spatial analysis in web GIS?
    a) The process of examining geographic patterns and relationships within geospatial data
    b) The process of converting addresses into geographic coordinates
    c) The process of visualizing geographic data on a map
    d) The process of sharing geographic data through the internet
    Answer: a

100. Which of the following is an example of a web mapping library?
     a) Leaflet
     b) Photoshop
     c) Excel
     d) Spotify
     Answer: a



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Accuracy assessment is the process of checking how correct your classified satellite image is . 👉 After supervised classification, the satellite image is divided into classes like: Water Forest Agriculture Built-up land Barren land But classification is done using computer algorithms, so some areas may be wrongly classified . 👉 Accuracy assessment helps to answer this question: ✔ "How much of my classified map is correct compared to real ground conditions?"  Goal The main goal is to: Measure reliability of classified maps Identify classification errors Improve classification results Provide scientific validity to research 👉 Without accuracy assessment, a classified map is not considered scientifically reliable . Reference Data (Ground Truth Data) Reference data is real-world information used to check classification accuracy. It can be collected from: ✔ Field survey using GPS ✔ High-resolution satellite images (Google Earth etc.) ✔ Existing maps or survey reports 🧭 Exampl...
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Atmospheric Window

The atmospheric window in remote sensing refers to specific wavelength ranges within the electromagnetic spectrum that can pass through the Earth's atmosphere relatively unimpeded. These windows are crucial for remote sensing applications because they allow us to observe the Earth's surface and atmosphere without significant interference from the atmosphere's constituents. Key facts and concepts about atmospheric windows: Visible and Near-Infrared (VNIR) window: This window encompasses wavelengths from approximately 0. 4 to 1. 0 micrometers. It is ideal for observing vegetation, water bodies, and land cover types. Shortwave Infrared (SWIR) window: This window covers wavelengths from approximately 1. 0 to 3. 0 micrometers. It is particularly useful for detecting minerals, water content, and vegetation health. Mid-Infrared (MIR) window: This window spans wavelengths from approximately 3. 0 to 8. 0 micrometers. It is valuable for identifying various materials, incl...
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Energy Interaction with Atmosphere and Earth Surface

In Remote Sensing , satellites record electromagnetic radiation (EMR) that is reflected or emitted from the Earth. Before reaching the sensor, radiation interacts with: The Atmosphere The Earth's Surface These interactions control how satellite images look and how we interpret them. I. Interaction of EMR with the Atmosphere When solar radiation travels from the Sun to the Earth, four main processes occur: 1. Absorption Definition: Absorption occurs when atmospheric gases absorb radiation at specific wavelengths and convert it into heat. Main absorbing gases: Ozone (O₃) → absorbs Ultraviolet (UV) Carbon dioxide (CO₂) → absorbs Thermal Infrared Water vapour (H₂O) → absorbs Infrared Concept: Atmospheric Windows These are wavelength regions where absorption is very low, allowing radiation to pass through the atmosphere. Remote sensing depends on these windows. For example, satellites like Landsat 8 use visible, near-infrared, and thermal bands located in atmospheric windows. 2. Trans...
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REMOTE SENSING INDICES

Remote sensing indices are band ratios designed to highlight specific surface features (vegetation, soil, water, urban areas, snow, burned areas, etc.) using the spectral reflectance properties of the Earth's surface. They improve classification accuracy and environmental monitoring. 1. Vegetation Indices NDVI – Normalized Difference Vegetation Index Formula: (NIR – RED) / (NIR + RED) Concept: Vegetation reflects strongly in NIR and absorbs in RED due to chlorophyll. Measures: Vegetation greenness & health Uses: Agriculture, drought monitoring, biomass estimation EVI – Enhanced Vegetation Index Formula: G × (NIR – RED) / (NIR + C1×RED – C2×BLUE + L) Concept: Corrects for soil and atmospheric noise. Measures: Vegetation vigor in dense canopies Uses: Tropical rainforest mapping, high biomass regions GNDVI – Green Normalized Difference Vegetation Index Formula: (NIR – GREEN) / (NIR + GREEN) Concept: Uses Green instead of Red ...
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Change Detection

Change detection is the process of finding differences on the Earth's surface over time by comparing satellite images of the same area taken on different dates . After supervised classification , two classified maps (e.g., Year-1 and Year-2) are compared to identify land use / land cover changes .  Goal To detect where , what , and how much change has occurred To monitor urban growth, deforestation, floods, agriculture, etc.  Basic Concept Forest → Forest = No change Forest → Urban = Change detected Key Terminologies Multi-temporal images : Images of the same area at different times Post-classification comparison : Comparing two classified maps Change matrix : Table showing class-to-class change Change / No-change : Whether land cover remains same or different Main Methods Post-classification comparison – Most common and easy Image differencing – Subtract pixel values Image ratioing – Divide pixel values Deep learning methods – Advanced AI-based detection Examples Agricult...
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