Questions and Answers
What does the symbol λ represent in the context of wave characteristics?
How is frequency (ν) defined?
What is the relationship between wavelength and frequency?
What are photons in the context of the particle model of light?
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What does Planck’s equation (Q = hν) indicate?
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What is the unit of frequency?
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Which statement correctly describes the inverse relationship between wavelength and frequency?
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What is the effect of thermal excitation on photons?
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What primarily causes the absorption of radiant energy in the atmosphere?
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What is an atmospheric window?
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How does scattering in the atmosphere affect remote sensing?
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Which type of scattering involves atmospheric molecules and is influenced by the wavelength of radiation?
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What effect does the atmosphere have on incoming and outgoing EM radiation?
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Why is diffuse reflectance important in remote sensing?
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What is a primary consequence of atmospheric absorption on remote sensing activities?
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What primarily influences the scattering of radiation in the atmosphere?
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What is the primary disadvantage of using radar instruments in microwave sensors?
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What does the term 'apogee' refer to in satellite orbits?
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Which of the following factors does NOT influence the spatial and temporal coverage of imagery from a satellite?
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What is the 'swath' in the context of satellite sensing?
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What does the term 'nadir' refer to?
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How is the inclination of a satellite's orbit generally measured?
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What is the difference between 'sidelap' and 'overlap' in satellite imagery?
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What defines the altitude of a satellite in its orbit?
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What is a key advantage of active remote sensing?
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Which equipment operates on the principle of active remote sensing?
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How does a whiskbroom scanner primarily operate?
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What characteristic wavelength does a typical radar altimeter operate at?
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What is true about passive remote sensing?
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What happens to clear water in optical remote sensing imagery?
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What characteristic of vegetation affects its appearance in optical remote sensing?
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What principle does the pushbroom scanner use?
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What is the primary purpose of precise image-to-image registration?
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What aspect can lead to misregistration when using location references in image registration?
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Which resampling method uses a distance weighted average of sixteen surrounding pixels?
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What are the two major radiometric corrections mentioned?
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What method significantly increases the speed of spatial domain correlation in image registration?
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How are pixel brightness values normalized during sun elevation correction?
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Which of the following factors does NOT influence radiance measurements?
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What is a common challenge in band-to-band registration of multispectral images?
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Study Notes
Wavelength & Frequency
- Wavelength (λ): Distance between successive crests/troughs, measured in meters, kilometers, etc.
- Frequency (ν): Number of wave cycles passing a fixed point per second, measured in Hertz (Hz).
- Inverse relationship: Longer wavelengths correspond to lower frequencies.
- Formula: λ = c/ν, where c is the speed of light.
Particle Model of Light
- Light is composed of photons, massless particles that transfer energy in discrete packets called quanta.
- Energy of a photon is determined by Planck’s equation: Q = hν, where h is Planck’s constant (6.6260×10^-34 J).
- Photons contribute to electromagnetic forces, carrying energy emitted by excited matter.
Light Interaction with the Atmosphere
- Atmosphere affects radiation intensity and spectral composition based on path length, energy magnitude, atmospheric conditions, and wavelength.
- Atmosphere modifies electromagnetic radiation through scattering, refraction, and absorption.
Absorption
- Primarily caused by ozone, carbon dioxide, and water vapor.
- Absorption converts radiant energy into other energy forms within the atmosphere or by targets.
- Atmospheric windows represent spectral regions minimally affected by absorption, allowing effective remote sensing.
Scattering
- Scattering: Diffusion of radiation influenced by particle size relative to radiation wavelength.
- Rayleigh scattering occurs with small particles, affecting remote sensing image quality by reducing contrast and altering spectral signatures.
Remote Sensing Methods
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Active Remote Sensing: Sensors transmit their own signals, measuring returned energy. These sensors operate regardless of time/season and use wavelengths not in solar spectrum.
- Example: Satellite Radar Altimetry operates at 13.5 GHz, measures time taken for pulses to return from Earth’s surface.
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Passive Remote Sensing: Measures natural radiation emitted or reflected by targets.
- Examples: Advanced Very High Resolution Radiometer (AVHRR), Sea-viewing Wide Field-of-View Sensor (SeaWiFS).
Sensor Classification
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Based on scanning processes:
- Whiskbroom scanners use rotating mirrors and build images point by point.
- Pushbroom scanners utilize an array of sensing elements and capture images line by line.
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Based on electromagnetic radiation (EMR) range:
- Optical sensors operate from 0.3 to 14 mm, useful for meteorological and ocean monitoring. Reflectivity varies by surface type (e.g., clear water appears dark).
- Microwave sensors penetrate atmospheric conditions, useful for detecting geological features and sea ice.
Satellite Orbits
- Key characteristics: orbital period, altitude, apogee/perigee, inclination, nadir/zenith, and swath width.
- Orbital periods can vary from 100 minutes to 24 hours.
- Altitudes classify satellites as low, moderate, or high (up to 36,000 km).
Image Registration
- Necessary for creating image mosaics, temporal change tracking, and multispectral image integration.
- Automatic digital registration uses correlation for overlapping areas to minimize misregistration errors.
Radiometric Corrections
- Influenced by viewing geometry, instrumental response, atmospheric conditions, and illumination changes.
- Key corrections include Earth-sun distance and sun elevation corrections to normalize pixel brightness values based on solar position.
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Description
This quiz explores the fundamental characteristics of wavelength and frequency in electromagnetic waves. It covers definitions, measurements, and the significance of these concepts in physics. Test your understanding of wave properties and their applications.
