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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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1. What Are Optical Sensors? Optical sensors are remote sensing instruments that detect solar radiation reflected or emitted from the Earth's surface in specific portions of the electromagnetic spectrum (EMS) . They mainly work in: Visible region (0.4–0.7 µm) Near-Infrared – NIR (0.7–1.3 µm) Shortwave Infrared – SWIR (1.3–3.0 µm) Thermal Infrared – TIR (8–14 µm) — emitted energy, not reflected Optical sensors capture spectral signatures of surface features. Each object reflects/absorbs energy differently, creating a unique spectral response pattern . a) Electromagnetic Spectrum (EMS) The continuous range of wavelengths. Optical sensing uses solar reflective bands and sometimes thermal bands . b) Spectral Signature The unique pattern of reflectance or absorbance of an object across wavelengths. Example: Vegetation reflects strongly in NIR Water absorbs strongly in NIR and SWIR (appears dark) c) Radiance and Reflectance Radi...

Platforms in Remote Sensing

In remote sensing, a platform is the physical structure or vehicle that carries a sensor (camera, scanner, radar, etc.) to observe and collect information about the Earth's surface. Platforms are classified mainly by their altitude and mobility : Ground-Based Platforms Definition : Sensors mounted on the Earth's surface or very close to it. Examples : Tripods, towers, ground vehicles, handheld instruments. Applications : Calibration and validation of satellite data Detailed local studies (e.g., soil properties, vegetation health, air quality) Strength : High spatial detail but limited coverage. Airborne Platforms Definition : Sensors carried by aircraft, balloons, or drones (UAVs). Altitude : A few hundred meters to ~20 km. Examples : Airplanes with multispectral scanners UAVs with high-resolution cameras or LiDAR High-altitude balloons (stratospheric platforms) Applications : Local-to-regional mapping ...

Radar Sensors in Remote Sensing

Radar sensors are active remote sensing instruments that use microwave radiation to detect and measure Earth's surface features. They transmit their own energy (radio waves) toward the Earth and record the backscattered signal that returns to the sensor. Since they do not depend on sunlight, radar systems can collect data: day or night through clouds, fog, smoke, and rain in all weather conditions This makes radar extremely useful for Earth observation. 1. Active Sensor A radar sensor produces and transmits its own microwaves. This is different from optical and thermal sensors, which depend on sunlight or emitted heat. 2. Microwave Region Radar operates in the microwave region of the electromagnetic spectrum , typically from 1 mm to 1 m wavelength. Common radar frequency bands: P-band (70 cm) L-band (23 cm) S-band (9 cm) C-band (5.6 cm) X-band (3 cm) Each band penetrates and interacts with surfaces differently: Lo...

Types of Remote Sensing

Remote Sensing means collecting information about the Earth's surface without touching it , usually using satellites, aircraft, or drones . There are different types of remote sensing based on the energy source and the wavelength region used. 🛰️ 1. Active Remote Sensing 📘 Concept: In active remote sensing , the sensor sends out its own energy (like a signal or pulse) to the Earth's surface. The sensor then records the reflected or backscattered energy that comes back from the surface. ⚙️ Key Terminology: Transmitter: sends energy (like a radar pulse or laser beam). Receiver: detects the energy that bounces back. Backscatter: energy that is reflected back to the sensor. 📊 Examples of Active Sensors: RADAR (Radio Detection and Ranging): Uses microwave signals to detect surface roughness, soil moisture, or ocean waves. LiDAR (Light Detection and Ranging): Uses laser light (near-infrared) to measure elevation, vegetation...

Thermal Sensors in Remote Sensing

Thermal sensors are remote sensing instruments that detect naturally emitted thermal infrared (TIR) radiation from the Earth's surface. Unlike optical sensors (which detect reflected sunlight), thermal sensors measure heat energy emitted by objects because of their temperature. They work mainly in the Thermal Infrared region (8–14 µm) of the electromagnetic spectrum. 1. Thermal Infrared Radiation All objects above 0 Kelvin (absolute zero) emit electromagnetic radiation. This is explained by Planck's Radiation Law . For Earth's surface temperature range (about 250–330 K), the peak emitted radiation occurs in the 8–14 µm thermal window . Thus, thermal sensors detect emitted energy , not reflected sunlight. 2. Emissivity Emissivity is the efficiency with which a material emits thermal radiation. Values range from 0 to 1 : Water, vegetation → high emissivity (0.95–0.99) Bare soil → medium (0.85–0.95) Metals → low (0.1–0.3) E...