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Questions and Answers
Remote sensing methods use active and passive sensors mounted on airborne platforms such as planes and ______.
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.
Optical EM spectrum includes visible light, near infrared, and ______ radiations.
shortwave infrared
Radar imageries use ______ EM radiations.
Radar imageries use ______ EM radiations.
microwave
Non imaging remote sensing methods include Radar ______ and Lidar.
Non imaging remote sensing methods include Radar ______ and Lidar.
Stereophotogrammetry is the classical way to produce DEMs from stereo pairs obtained by ______ remote sensing.
Stereophotogrammetry is the classical way to produce DEMs from stereo pairs obtained by ______ remote sensing.
The primary advantage of stereo imagery is the ability to extract geographic features in ______.
The primary advantage of stereo imagery is the ability to extract geographic features in ______.
In the manual method of stereophotogrammetry, an operator uses a ______ to view a pair of stereophotos.
In the manual method of stereophotogrammetry, an operator uses a ______ to view a pair of stereophotos.
The automated method of stereophotogrammetry calculates the ______ displacement of points.
The automated method of stereophotogrammetry calculates the ______ displacement of points.
The PRISM and CARTOSAT-1 satellites provide high resolution data with a resolution of ______ meters.
The PRISM and CARTOSAT-1 satellites provide high resolution data with a resolution of ______ meters.
UAVs can be equipped with various types of sensors including visible band, multispectral, thermal cameras, and ______.
UAVs can be equipped with various types of sensors including visible band, multispectral, thermal cameras, and ______.
Laser altimetry, also known as ______, is a technique used for active remote sensing.
Laser altimetry, also known as ______, is a technique used for active remote sensing.
The returned laser pulses in LiDAR allow for the calculation of the distance from the ground surface considering the speed of ______.
The returned laser pulses in LiDAR allow for the calculation of the distance from the ground surface considering the speed of ______.
Satellite laser altimetry is widely used for generating ______.
Satellite laser altimetry is widely used for generating ______.
UAV photogrammetry offers a low-cost alternative to manned aerial ______.
UAV photogrammetry offers a low-cost alternative to manned aerial ______.
LiDAR aerial surveys can create high-resolution DEMs down to ______ meters in clear waters.
LiDAR aerial surveys can create high-resolution DEMs down to ______ meters in clear waters.
The quasi-global ASTER GDEM was produced by processing stereo pairs from the ______ satellite.
The quasi-global ASTER GDEM was produced by processing stereo pairs from the ______ satellite.
Costs for producing DEMs from PRISM and CARTOSAT-1 are lower than ______ USD per square kilometer.
Costs for producing DEMs from PRISM and CARTOSAT-1 are lower than ______ USD per square kilometer.
Recent advancements have allowed UAVs to be used increasingly for ______ sensing.
Recent advancements have allowed UAVs to be used increasingly for ______ sensing.
Current bathymetric charts are inadequate because only a small fraction of the seafloor has been ______.
Current bathymetric charts are inadequate because only a small fraction of the seafloor has been ______.
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 ______.
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 ______.
Echo sounding techniques are used to determine the distance between the water surface and underwater ______.
Echo sounding techniques are used to determine the distance between the water surface and underwater ______.
The depth of water in echo sounding is determined from the time lag between the emission and return of a ______.
The depth of water in echo sounding is determined from the time lag between the emission and return of a ______.
Common single-beam echo sounders transmit a single beam oriented toward the vessel’s ______.
Common single-beam echo sounders transmit a single beam oriented toward the vessel’s ______.
More detailed DEMs are derived using ______.
More detailed DEMs are derived using ______.
LiDAR point measurements will render Digital Surface Models (DSM), which contains information on all objects including ______.
LiDAR point measurements will render Digital Surface Models (DSM), which contains information on all objects including ______.
Through sophisticated algorithms, landscape elements are removed to generate a Digital ______ Model (DTM).
Through sophisticated algorithms, landscape elements are removed to generate a Digital ______ Model (DTM).
The average costs of LiDAR range from ______ to 800 US$/km2.
The average costs of LiDAR range from ______ to 800 US$/km2.
SAR is a group of active remote sensing techniques that transmits electromagnetic radiation at ______ frequencies.
SAR is a group of active remote sensing techniques that transmits electromagnetic radiation at ______ frequencies.
To produce DEMs using SAR, techniques such as interferometry and ______ using stereo pairs of radar images can be applied.
To produce DEMs using SAR, techniques such as interferometry and ______ using stereo pairs of radar images can be applied.
The most common InSAR techniques utilize phase-difference measurements derived from ______ radar images.
The most common InSAR techniques utilize phase-difference measurements derived from ______ radar images.
The InSAR technique was applied in the Shuttle Radar Topography Mission to prepare ______ Global DEMs.
The InSAR technique was applied in the Shuttle Radar Topography Mission to prepare ______ Global DEMs.
These resolutions correspond to about 1 km, 500 m, 100 m, and ______ m respectively.
These resolutions correspond to about 1 km, 500 m, 100 m, and ______ m respectively.
SAR-based DEMs are utilized in medium- and small-scale mapping of ______ areas.
SAR-based DEMs are utilized in medium- and small-scale mapping of ______ areas.
The large one-pass spaceborne SAR interferometer is based on two similar radar satellites, TerraSAR-X and ______.
The large one-pass spaceborne SAR interferometer is based on two similar radar satellites, TerraSAR-X and ______.
DEMs can be derived using radar satellites such as RADARSAT, TerraSAR-X, and ______.
DEMs can be derived using radar satellites such as RADARSAT, TerraSAR-X, and ______.
Synthetic Aperture Radar Interferometry (InSAR) is primarily used for detecting changes in topographic heights related to ______ geological processes.
Synthetic Aperture Radar Interferometry (InSAR) is primarily used for detecting changes in topographic heights related to ______ geological processes.
Satellite radar altimetry measures height by sending out short pulses of ______ energy.
Satellite radar altimetry measures height by sending out short pulses of ______ energy.
One application of satellite radar altimetry is calculating the height of ocean and ______.
One application of satellite radar altimetry is calculating the height of ocean and ______.
The Jason-2 Ocean Surface Topography Mission, launched in 2008, carries the Poseidon-3 Radar ______.
The Jason-2 Ocean Surface Topography Mission, launched in 2008, carries the Poseidon-3 Radar ______.
In satellite radar altimetry, the received back echoes or reflections are measured to correct for potential error sources such as changes in ______.
In satellite radar altimetry, the received back echoes or reflections are measured to correct for potential error sources such as changes in ______.
Satellite radar altimeters are also used to reveal marine gravity ______.
Satellite radar altimeters are also used to reveal marine gravity ______.
Ship track echo-sounding data are often too sparse to fully define submarine ______.
Ship track echo-sounding data are often too sparse to fully define submarine ______.
To accurately determine the satellite’s position in space, the Jason-2 mission employs advanced ______.
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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