Remote Sensing & GIS
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Questions and Answers

What is the purpose of the Normalized Difference Vegetation Index (NDVI)?

  • To track urbanization rates
  • To assess soil contamination
  • To measure rainfall patterns
  • To monitor changes in vegetation health (correct)

    • Phenology only studies animal life cycles.

    False

    What does the Vegetation Condition Index (VCI) measure?

    NDVI changes to assess drought conditions

    The process of __________ monitors shifts in data patterns using image differencing techniques.

    <p>Change Detection</p> Signup and view all the answers

    Match the following applications of temporal series analysis with their corresponding areas:

    <p>Crop yield forecasting = Biosphere/Agriculture Biodiversity mapping = Nature Glacier monitoring = Cryosphere Air quality assessment = Atmosphere</p> Signup and view all the answers

    Which of the following forms of electromagnetic radiation is used primarily in polarimetric radar systems for moisture sensing?

    <p>Microwaves</p> Signup and view all the answers

    Specular reflection occurs when light scatters irregularly on rough surfaces.

    <p>False</p> Signup and view all the answers

    What role does chlorophyll play in the behavior of electromagnetic radiation in vegetation?

    <p>Chlorophyll absorbs visible light.</p> Signup and view all the answers

    In remote sensing, the ___ defines the area covered by a single pixel.

    <p>Instantaneous Field of View (IFOV)</p> Signup and view all the answers

    Match the remote sensing technique with its description:

    <p>Passive Remote Sensing = Captures radiation reflected or emitted by objects Active Remote Sensing = Emits signals and records responses LIDAR = Uses laser beams for measurements RADAR = Uses radio waves for distance measuring</p> Signup and view all the answers

    What characteristic of soils affects their reflectivity in the visible and near-infrared spectra?

    <p>Organic content</p> Signup and view all the answers

    X-rays and gamma rays are commonly used in remote sensing applications.

    <p>False</p> Signup and view all the answers

    How do snow and ice compare in terms of reflectivity in the visible light and near-infrared spectra?

    <p>They are similar in visible light but distinguishable in other wavelengths.</p> Signup and view all the answers

    What is the primary difference between vector and raster data?

    <p>Vector data represents data as points, lines, or polygons, while raster data uses grids or images.</p> Signup and view all the answers

    The Geographic Coordinate System (GCS) provides higher accuracy for small area mapping compared to Projected Coordinate Systems (PCS).

    <p>False</p> Signup and view all the answers

    What is the purpose of gap filling in temporal series data?

    <p>To impute missing data using ancillary or neighboring data.</p> Signup and view all the answers

    Raster data is represented as ______ or images, where each cell has a fixed size.

    <p>grids</p> Signup and view all the answers

    Match the following types of temporal series with their description:

    <p>Multi-annual = Spanning multiple years Intra-annual = Within a single year High-temporal frequency = Observations taken frequently, within days to weeks Trend analysis = Identifying long-term patterns over time</p> Signup and view all the answers

    What projection system is ideal for mapping regions using a cylindrical method?

    <p>Universal Transverse Mercator (UTM)</p> Signup and view all the answers

    Smoothing methods are used in temporal series to reduce noise while preserving key data patterns.

    <p>True</p> Signup and view all the answers

    What type of filtering maintains features like maxima and minima in temporal series data?

    <p>Smart Filtering or Savitzky-Golay Filtering.</p> Signup and view all the answers

    What is the main function of satellites in remote sensing?

    <p>To carry instruments that measure electromagnetic radiation</p> Signup and view all the answers

    Electromagnetic radiation only includes the wavelengths visible to the human eye.

    <p>False</p> Signup and view all the answers

    What does NDVI stand for and what does it indicate about vegetation health?

    <p>Normalized Difference Vegetation Index, indicating how healthy the vegetation is.</p> Signup and view all the answers

    The spectral signature is the unique way different materials __________ electromagnetic radiation.

    <p>reflect</p> Signup and view all the answers

    Match the following materials to their reflectance characteristics:

    <p>Vegetation = Absorbs red light and reflects NIR Water = Absorbs longer visible wavelengths Soil = Reflects based on moisture content Atmosphere = Scatters and absorbs energy</p> Signup and view all the answers

    Which of the following is a key factor in the behavior of radiation when it interacts with the atmosphere?

    <p>Radiation can be absorbed and scattered by gases and aerosols</p> Signup and view all the answers

    The absorption of longer visible wavelengths by water makes it appear mostly blue.

    <p>True</p> Signup and view all the answers

    What adjustments must be made to satellite images before they can be used?

    <p>Corrections for atmospheric interference.</p> Signup and view all the answers

    What is the main function of atmospheric correction in remote sensing?

    <p>To remove scattering and absorption effects from the atmosphere</p> Signup and view all the answers

    Remote sensing data can include vector data.

    <p>False</p> Signup and view all the answers

    What is the primary output of remote sensing?

    <p>Derived products or satellite images</p> Signup and view all the answers

    The first European Sentinel mission was launched in _____.

    <p>2014</p> Signup and view all the answers

    Match the following resolutions with their definitions:

    <p>Spatial Resolution = The size of the smallest feature that can be detected Temporal Resolution = The frequency at which data is collected Spectral Resolution = The ability to resolve different wavelengths Radiometric Resolution = The ability to discriminate between small differences in energy levels</p> Signup and view all the answers

    Which of the following statements about GIS is true?

    <p>GIS can be expensive to implement</p> Signup and view all the answers

    Drones have a global coverage capability similar to satellites.

    <p>False</p> Signup and view all the answers

    What is a disadvantage of remote sensing?

    <p>Difficult to obtain high resolutions simultaneously across all dimensions</p> Signup and view all the answers

    In 1972, NASA released the first Earth Observation satellite called _____.

    <p>ERTS-1</p> Signup and view all the answers

    What does GIS integrate with to enhance its functionalities?

    <p>Geographical databases</p> Signup and view all the answers

    Match the following terms with their correct definitions:

    <p>Raster Data = Data represented as a grid of pixels Vector Data = Data represented as geometric shapes Geometric Corrections = Adjustments made for distortions Radiometric Corrections = Converting digital numbers to radiance or reflectance</p> Signup and view all the answers

    The Landsat archive became open for public access in 2008.

    <p>True</p> Signup and view all the answers

    What is the process of applying satellite data typically require?

    <p>Additional processing, visualization, and other tools</p> Signup and view all the answers

    GIS is an organized collection of tools for managing, analyzing, and communicating spatially referenced _____.

    <p>data</p> Signup and view all the answers

    What are UAVs primarily known for in remote sensing?

    <p>Offering good spatial resolution over small areas</p> Signup and view all the answers

    What is the relationship between wavelength and frequency in electromagnetic waves?

    <p>Higher wavelength correlates with lower frequency</p> Signup and view all the answers

    Electromagnetic waves can be absorbed, transmitted, or scattered.

    <p>True</p> Signup and view all the answers

    A __________ reflects light uniformly in all directions, making it equally bright independent of the angle of view.

    <p>Lambert surface</p> Signup and view all the answers

    Match the electromagnetic radiation type with its application:

    <p>Microwaves = Soil moisture sensing Infrared = Thermal imaging Ultraviolet = Planetary atmosphere studies X-rays = Medical imaging</p> Signup and view all the answers

    Which of the following is a property of electromagnetic polarization?

    <p>It specifies the geometrical orientation of oscillations</p> Signup and view all the answers

    Which parameter is NOT a component of radiometric calibration?

    <p>Spectral Range</p> Signup and view all the answers

    LIDAR is an example of a passive sensor.

    <p>False</p> Signup and view all the answers

    Atmospheric corrections are performed to obtain surface radiance values accurately.

    <p>True</p> Signup and view all the answers

    What happens when an electromagnetic wave hits a conductor?

    <p>It transforms into heat and reflects on the surface.</p> Signup and view all the answers

    The formula relating the speed of light, frequency, and wavelength is given by: speed of light = __________ × wavelength.

    <p>frequency</p> Signup and view all the answers

    What type of white reference is necessary for effective calibration?

    <p>Optical white reference</p> Signup and view all the answers

    The first calibration step is known as __________ calibration.

    <p>pre-flight</p> Signup and view all the answers

    Which phenomenon occurs when light passes from one medium to another?

    <p>Refraction</p> Signup and view all the answers

    Which atmospheric correction algorithm is the most commonly used?

    <p>MODTRAN</p> Signup and view all the answers

    Thermal radiation is emitted by objects only when they are at absolute zero temperature.

    <p>False</p> Signup and view all the answers

    Level 0 satellite data consists of georeferenced and calibrated data.

    <p>False</p> Signup and view all the answers

    What is the purpose of image enhancement techniques?

    <p>To improve visualization and interpretation of images.</p> Signup and view all the answers

    What is the defining characteristic of a blackbody?

    <p>It absorbs all incident electromagnetic energy.</p> Signup and view all the answers

    The energy carried by electromagnetic radiation is referred to as __________ energy.

    <p>radiant</p> Signup and view all the answers

    Match the following levels of image processing with their descriptions:

    <p>Level 0 = Raw instrument data Level 1 = Time-referenced raw data Level 2 = Calibrated geophysical data Level 3 = Uniform geospatial data</p> Signup and view all the answers

    What does the gain relate to in radiometric calibration?

    <p>Normalized maximum and minimum digital numbers</p> Signup and view all the answers

    How does vegetation affect electromagnetic radiation in the near-infrared wavelengths?

    <p>Vegetation is highly reflective and transmissive</p> Signup and view all the answers

    Satellite data processing levels are universally named the same by all space agencies.

    <p>False</p> Signup and view all the answers

    What are the main types of interactions in the optical range of the spectrum?

    <p>Dispersion</p> Signup and view all the answers

    The __________ provides a way to visualize satellite data using multispectral information.

    <p>colour composition</p> Signup and view all the answers

    Which of the following describes the process of radiometric correction?

    <p>Compensating for atmospheric effects</p> Signup and view all the answers

    Match the image processing techniques with their purposes:

    <p>Contrast adjustment = Enhancing image visibility Principal components analysis = Reducing dimensionality for classification Segmentation = Dividing images into meaningful parts Colour composites = Visualizing multispectral information</p> Signup and view all the answers

    What primarily affects the reflectivity of leaves in remote sensing?

    <p>The presence of chlorophyll</p> Signup and view all the answers

    Active remote sensing sensors can only capture information but not emit it.

    <p>False</p> Signup and view all the answers

    What is the purpose of georeferencing in image processing?

    <p>To correlate image values with ground coordinates.</p> Signup and view all the answers

    In remote sensing, the __________ of View (FOV) determines the area that an image covers.

    <p>Field</p> Signup and view all the answers

    Match the types of remote sensing with their descriptions:

    <p>Passive remote sensing = Detects emitted or reflected signals without emitting any signals. Active remote sensing = Emits a signal and records its interaction with observed systems. Spectrometers = Instruments that measure the spectrum of light. LIDAR = Senses the distance to a target using laser light.</p> Signup and view all the answers

    Which of the following is true about the instantaneous field of view (IFOV)?

    <p>It determines the spatial resolution of an image.</p> Signup and view all the answers

    Water absorbs almost all energy in the near-infrared (NIR) and mid-infrared (IR) spectrum.

    <p>True</p> Signup and view all the answers

    What is a common method used to filter noise in image restoration?

    <p>Median filters</p> Signup and view all the answers

    The swath of the image refers to the __________ area covered by an image.

    <p>area</p> Signup and view all the answers

    What is the relationship between spatial resolution and spectral resolution?

    <p>High spatial resolution is accompanied by low spectral resolution.</p> Signup and view all the answers

    Control points are used to adjust an image to a georeferenced map.

    <p>True</p> Signup and view all the answers

    What is spectral radiance in the context of remote sensing?

    <p>The radiant flux emitted or reflected by a surface per unit solid angle per unit projected area.</p> Signup and view all the answers

    In image processing, __________ corrects distortions in satellite images to fit them accurately to the earth's surface.

    <p>geometric corrections</p> Signup and view all the answers

    Match the image processing techniques with their descriptions:

    <p>Restoration = Recovering lost pixel values in image acquisition. Preprocessing = Performing corrections for geometry, atmosphere, or radiometry. Resampling = Transforming digital numbers to the same projection. Radiometric correction = Converting sensor measurements to physical magnitudes.</p> Signup and view all the answers

    Which method calculates the average of four neighboring pixels during resampling?

    <p>Bilinear</p> Signup and view all the answers

    Which of the following satellite orbits allows for a constant view of the same area on Earth?

    <p>Geosynchronous Orbit</p> Signup and view all the answers

    MODIS has a spatial resolution of 500 meters for thermal infrared imaging.

    <p>False</p> Signup and view all the answers

    What is the primary focus of Sentinel 1 satellites?

    <p>Radar imaging</p> Signup and view all the answers

    Sentinel 2 is primarily used for _______ imaging.

    <p>optical</p> Signup and view all the answers

    Which of the following is NOT a characteristic of raster data?

    <p>Uses vector geometry</p> Signup and view all the answers

    The Sentinel 5 satellite focuses on measuring the chemistry composition of the atmosphere.

    <p>True</p> Signup and view all the answers

    What challenges do clouds present for optical remote sensing methods?

    <p>They obscure the view of the Earth's surface.</p> Signup and view all the answers

    Match the following satellite systems with their primary purpose:

    <p>Sentinel 3 = Multiple sensing instruments for various data Landsat 8 = Understanding historical Earth changes Sentinel 1 = Radar imaging for floods and land changes MODIS = High temporal resolution for global coverage</p> Signup and view all the answers

    In the context of the Earth, __________ refers to a mathematical model used to describe its shape.

    <p>geoid</p> Signup and view all the answers

    What is a limitation of raster data when working with GIS applications?

    <p>May lose location information when opened in non-GIS software</p> Signup and view all the answers

    What does Hue (H) represent in HSI color representation?

    <p>The actual color</p> Signup and view all the answers

    NDVI values can range from -1 to 1.

    <p>True</p> Signup and view all the answers

    What indicates that there are no green leaves in an area based on NDVI values?

    <p>NDVI values between -1 and 0 indicate no green leaves.</p> Signup and view all the answers

    HSI stands for __________, Saturation, and Intensity.

    <p>Hue</p> Signup and view all the answers

    Which of the following methods can be used for supervised classification?

    <p>Maximum likelihood</p> Signup and view all the answers

    The Principal Components Analysis (PCA) reduces data dimensions while retaining the most information.

    <p>True</p> Signup and view all the answers

    What are the principal components in PCA calculated through?

    <p>Linear combination of bands.</p> Signup and view all the answers

    The __________ is the smallest geometrical unit of a dataset containing spectral information.

    <p>pixel</p> Signup and view all the answers

    Match the following classification methods with their characteristics:

    <p>Maximum Likelihood = Determines class centroid based on probability K-nearest Neighbour = Classifies pixels based on proximity to known samples Minimum Distance = Classifies based on distance to class centroids Isodata Clustering = Unsupervised clustering method</p> Signup and view all the answers

    How can the overall accuracy of land classification systems be calculated?

    <p>Sum of diagonal values divided by the grand total</p> Signup and view all the answers

    Nonparametric classification uses a mathematical function.

    <p>False</p> Signup and view all the answers

    What can NDVI indicate if it is close to 1?

    <p>High density of green leaves.</p> Signup and view all the answers

    The process that tracks seasonal changes in vegetation is called __________.

    <p>remote sensing</p> Signup and view all the answers

    In pixelwise classification, what does one pixel represent?

    <p>The smallest unit in a dataset</p> Signup and view all the answers

    Broadleaf trees and needle trees exhibit similar NDVI values.

    <p>False</p> Signup and view all the answers

    Study Notes

    Remote Sensing

    • Definition: Acquiring data about Earth's surface from a distance using electromagnetic radiation. Analyzing reflected or emitted radiation.
    • Operation: Satellites and sensors measure electromagnetic radiation across various wavelengths. Atmospheric corrections are applied to adjust for interference. Different materials have unique spectral signatures, enabling the identification of features.
    • Key examples of analysis include vegetation (using NDVI), water, and other surface characteristics.
    • History:
      • 1957: Sputnik launch.
      • 1972: Landsat-1, the first Earth observation satellite, initiated systematic multispectral satellite imaging.
      • 2008: Landsat archive became open access.
      • 2012: Google Earth Engine launched.
      • Recent ESA missions (e.g., Sentinel-2 in 2015) and private planetary computing platforms.

    Types of Satellites

    • Orbits: Polar or geostationary.
    • Energy Source: Passive (external energy) or active (onboard energy, e.g., radar).
    • Resolution types: Spatial, temporal, spectral, and radiometric.

    Geographic Information Systems (GIS)

    • Definition: Managing, analyzing and visualizing spatial data using tools and integrated databases. Often in raster or vector formats.
    • History:
      • 1970s: Rise of GIS systems like MOSS, GRASSGIS, and commercial platforms like CARIS and ERDAS.
      • 1983: First commercial software (Odyssey)
      • Late 20th century: Internet-based GIS data and open-source software like QGIS emerged.
      • 21st century: Integration with cloud computing, relational databases, and software-as-a-service platforms.
    • Advantages: Supports diverse data formats and hardware/software, facilitates record-keeping of geographical changes.
    • Disadvantages: Requires prior knowledge in related fields and can be expensive to implement, prone to errors due to significant data needs.

    Electromagnetic Radiation & Remote Sensing

    • Electromagnetic waves comprise oscillating electric and magnetic fields that propagate through space.
    • Key properties include Amplitude (maximum displacement from equilibrium), Wavelength (distance between equivalent points), Frequency (number of oscillations per second), Period (time for successive peaks to pass a point), and Propagation Speed (speed of light).
    • Wave phenomena include refraction, diffraction, scattering, and polarization.
    • Electromagnetic waves exhibit wave-particle duality.
    • Higher wavelength means lower photon energy.

    Electromagnetic Spectrum Applications

    • Radio waves (RADAR, LIDAR): Measuring distances and soil moisture.
    • Microwaves: Moisture sensing.
    • Infrared and visible light: Spectrometers, lasers, highly reflective features for vegetation and soils.
    • Ultraviolet radiation: Limited to planetary studies.
    • X-rays and gamma rays: Rarely used due to atmospheric opacity.

    Data Acquisition & Image Processing

    • Passive Remote Sensing: Captures reflected/emitted radiation (e.g., LANDSAT, MODIS, Sentinel-2) spanning visible, infrared, thermal, and microwave ranges (spectrometers, radiometers, cameras).
    • Active Remote Sensing: Emits signals and records interactions, e.g., LIDAR, RADAR, Sentinel-1 (primarily microwave).
    • Image processing operations:
      • Field of View (FOV) and Instantaneous Field of View (IFOV): Spatial resolution.
      • Image Composition: Matrices of digital numbers per pixel per filter, often transforming to physical reflectance values.
      • Sensor Characteristics: High spatial resolution implies low spectral resolution (captures discrete wavelengths only).

    Image Processing Steps

    • Restoration: Correcting missing data using filters like median filters.
    • Pre-processing:
      • Geometric corrections: Aligning images with the Earth using control points, georeferencing, and resampling techniques.
      • Radiometric corrections: Converting digital numbers (DNs) to radiance using calibration. Reflectance at the top of the atmosphere: calculated as (DNxGain) + Bias.

    Atmospheric Corrections

    • Removes atmospheric distortions from surfaces using algorithms like ATCOR, 6S, and MODTRAN.

    Enhancement

    • Improving image quality for color and contrast adjustments using techniques like Principal Components Analysis (PCA).

    Derivative Products

    • Outputting information like land cover classifications and segmentations.

    Image Processing Levels

    • Level 0-1: Raw data (DN Values), time-referenced.
    • Level 2: Georeferenced and calibrated data.
    • Level 3: Processed data, uniformly gridded and averaged for specific time/geographic areas.
    • Level 4: combines Level 3 data with other datasets.

    Image Enhancement

    • Contrast adjustments to enhance visualizations.
    • Color composites creating visualized multispectral imagery using RGB layers. Transformations like RGB-to-HSI represent color using Hue, Saturation, and Intensity (brightness)..

    Transformations

    • NDVI (Normalized Difference Vegetation Index): Assessing vegetation health using red and near-infrared bands.
    • PCA (Principal Components Analysis): Reducing multispectral data dimensionality.
    • Image Classification: Supervised or unsupervised methods, classifying pixels based on their spectral characteristics.
    • Parametric classifications use mathematical functions like Maximum Likelihood or Minimum Distance.
    • Non-parametric classifications involve techniques such as k-means clustering or decision trees

    Platforms for Remote Sensing

    • Ground-Based: Drones, backpacks for calibration.
    • Airborne: Planes for regional analysis.
    • Space-based: Satellites in various orbits (LEO, GEO, Polar, highly elliptical).

    Key Satellites and Sensors

    • Landsat: Leading satellite program for Earth's surface data.
    • MODIS and Sentinel (ESA): High temporal and spatial resolution satellites encompassing a variety of data types.

    Geographic Information Systems (GIS)

    • GIS Data Types: Vector and raster data.
      • Vector Data: Represents data as points, lines, or polygons.
      • Raster Data: Represents data as grids or images (pixels).

    Projections and Coordinate Systems

    • Earth's shape: Irregular, modeled with ellipsoids.
    • Datum: Serves as reference point for models.
    • Geographic Coordinate System (GCS): Uses latitude and longitude.
    • Projected Coordinate System (PCS): Optimized for specific regions; units like meters.
    • UTM (Universal Transverse Mercator): Cylindrical projection for mapping regions.

    Temporal Series

    • Definition: A sequence of data points collected over time (regular or irregular intervals), in remote sensing including frequent observations for every pixel.
    • Types: Multi-annual, Intra-annual.
    • Key Techniques: High-temporal frequency observations, Smoothing methods (median smoothing, moving average), Trend analysis.
    • Pre-processing in Temporal Series: Gap Filling (imputing missing data), Smoothing (using statistical filters), Smart Filtering.

    Phenology and Remote Sensing

    • Phenology: Studies life cycles of plants and animals relative to seasons, starting and ending of seasons (SOS and EOS).

    Anomalies in Temporal Series

    • Definition: Deviations from normal conditions (e.g., rainfall, NDVI).
    • Calculation Methods: Absolute difference, relative difference, standardized anomalies or z-scores.
    • Vegetation Condition Index (VCI): Measures NDVI changes.

    Change Detection

    • Identifying changes using image differencing techniques (urbanization, deforestation, glacier loss).

    Applications of Temporal Series Analysis

    • Broad applications within biosphere (agriculture, forest), nature (biodiversity, carbon stock), pedosphere (soil), atmosphere (air quality, climate), hydrosphere (water), cryosphere (glaciers), and numerous other areas (archaeology, fire detection, epidemiology.)

    • NDVI changes to assess drought conditions

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    Test your knowledge on remote sensing, its definitions, operations, and historical milestones. Delve into how satellites gather data about Earth's surface and discover the different types of satellites used in this field. This quiz will cover essential concepts and examples relevant to understanding remote sensing technology.

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