Questions and Answers
Remote sensing methods use active and passive sensors mounted on airborne platforms such as planes and ______.
drones
Optical EM spectrum includes visible light, near infrared, and ______ radiations.
shortwave infrared
Radar imageries use ______ EM radiations.
microwave
Non imaging remote sensing methods include Radar ______ and Lidar.
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Stereophotogrammetry is the classical way to produce DEMs from stereo pairs obtained by ______ remote sensing.
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The primary advantage of stereo imagery is the ability to extract geographic features in ______.
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In the manual method of stereophotogrammetry, an operator uses a ______ to view a pair of stereophotos.
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The automated method of stereophotogrammetry calculates the ______ displacement of points.
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The PRISM and CARTOSAT-1 satellites provide high resolution data with a resolution of ______ meters.
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UAVs can be equipped with various types of sensors including visible band, multispectral, thermal cameras, and ______.
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Laser altimetry, also known as ______, is a technique used for active remote sensing.
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The returned laser pulses in LiDAR allow for the calculation of the distance from the ground surface considering the speed of ______.
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Satellite laser altimetry is widely used for generating ______.
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UAV photogrammetry offers a low-cost alternative to manned aerial ______.
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LiDAR aerial surveys can create high-resolution DEMs down to ______ meters in clear waters.
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The quasi-global ASTER GDEM was produced by processing stereo pairs from the ______ satellite.
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Costs for producing DEMs from PRISM and CARTOSAT-1 are lower than ______ USD per square kilometer.
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Recent advancements have allowed UAVs to be used increasingly for ______ sensing.
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Current bathymetric charts are inadequate because only a small fraction of the seafloor has been ______.
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Airborne optical sensing is based on the principle that the total amount of radiative energy reflected from a water column is a function of water ______.
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Echo sounding techniques are used to determine the distance between the water surface and underwater ______.
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The depth of water in echo sounding is determined from the time lag between the emission and return of a ______.
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Common single-beam echo sounders transmit a single beam oriented toward the vessel’s ______.
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More detailed DEMs are derived using ______.
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LiDAR point measurements will render Digital Surface Models (DSM), which contains information on all objects including ______.
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Through sophisticated algorithms, landscape elements are removed to generate a Digital ______ Model (DTM).
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The average costs of LiDAR range from ______ to 800 US$/km2.
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SAR is a group of active remote sensing techniques that transmits electromagnetic radiation at ______ frequencies.
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To produce DEMs using SAR, techniques such as interferometry and ______ using stereo pairs of radar images can be applied.
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The most common InSAR techniques utilize phase-difference measurements derived from ______ radar images.
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The InSAR technique was applied in the Shuttle Radar Topography Mission to prepare ______ Global DEMs.
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These resolutions correspond to about 1 km, 500 m, 100 m, and ______ m respectively.
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SAR-based DEMs are utilized in medium- and small-scale mapping of ______ areas.
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The large one-pass spaceborne SAR interferometer is based on two similar radar satellites, TerraSAR-X and ______.
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DEMs can be derived using radar satellites such as RADARSAT, TerraSAR-X, and ______.
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Synthetic Aperture Radar Interferometry (InSAR) is primarily used for detecting changes in topographic heights related to ______ geological processes.
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Satellite radar altimetry measures height by sending out short pulses of ______ energy.
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One application of satellite radar altimetry is calculating the height of ocean and ______.
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The Jason-2 Ocean Surface Topography Mission, launched in 2008, carries the Poseidon-3 Radar ______.
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In satellite radar altimetry, the received back echoes or reflections are measured to correct for potential error sources such as changes in ______.
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Satellite radar altimeters are also used to reveal marine gravity ______.
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Ship track echo-sounding data are often too sparse to fully define submarine ______.
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To accurately determine the satellite’s position in space, the Jason-2 mission employs advanced ______.
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Study Notes
Remote Sensing Methods
- Utilize active and passive sensors mounted on airborne (planes, drones) or spaceborne (satellites, space shuttles) platforms.
- Employ optical and microwave portions of the electromagnetic spectrum for imagery.
- Optical spectrum includes visible light, near-infrared, and shortwave infrared; utilized for stereo photogrammetry.
- Microwave spectrum is leveraged for radar imagery.
Stereophotogrammetry Method
- Classical technique for DEM production using stereo pairs from optical remote sensing.
- Can be performed manually or automatically; manual involves stereoplotters, automatic utilizes parallax displacement calculations.
- High-resolution data sources include PRISM (ALOS) and CARTOSAT-1, achieving costs under 10 USD/km².
- Data can be acquired from the same or different satellite platforms.
Laser Altimetry (LiDAR) Method
- Active remote sensing technique that uses laser pulses to calculate ground distances.
- Generates high-resolution Digital Surface Models (DSM) and Digital Terrain Models (DTM) by processing LiDAR point measurements.
- Accuracy can reach within 3 cm for well-defined surfaces, with costs ranging from 300 to 800 USD/km².
Synthetic Aperture Radar (SAR) Method
- Active remote sensing technique transmitting microwave radiation, capturing echoes to produce DEMs.
- Applies four techniques: interferometry, stereoscopy, polarimetry, and clinometry, with interferometric SAR (InSAR) being the most common.
- Significant outputs include SRTM Global DEMs with resolutions varying from 30” to 1” for large-area medium to small-scale mapping.
Satellite Radar Altimetry Method
- Active sensing technique that calculates Earth heights using microwave energy pulses.
- Common applications include ocean and inland water measurement; exemplified by the Jason-2 mission.
- Useful for analyzing sea surface shape and marine gravity anomalies.
Airborne Optical Sensing of Bathymetry Method
- Passive method estimating water depth through radiative energy reflection.
- Suited for shallow seafloor DEM generation under clear water conditions.
- Primarily applicable for nautical navigation safety and hazard mapping.
Echo Sounding Method
- Active hydrographic technique employing sonar to measure underwater topography.
- Determines water depth through sound pulse emission and return time lag.
- Implemented through single-beam, multibeam, and side scan systems for varied measurement needs.
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Description
Explore Chapter 2 of CE 797 focusing on Digital Elevation Models (DEMs) and their applications in GIS within Civil Engineering. This quiz will cover remote sensing methods, including the use of airborne platforms. Test your understanding of the key concepts presented in this lecture.
