Podcast
Questions and Answers
What type of sensors are used in remote sensing methods?
What type of sensors are used in remote sensing methods?
Which electromagnetic spectrum radiations are used in optical remote sensing?
Which electromagnetic spectrum radiations are used in optical remote sensing?
What is the main advantage of using stereo imagery in DEM production?
What is the main advantage of using stereo imagery in DEM production?
How can stereophotogrammetry be performed?
How can stereophotogrammetry be performed?
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What does the automated method in stereophotogrammetry calculate?
What does the automated method in stereophotogrammetry calculate?
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Which of the following methods is NOT considered a part of remote sensing?
Which of the following methods is NOT considered a part of remote sensing?
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What type of imagery is primarily used to generate DEMs using stereophotogrammetry?
What type of imagery is primarily used to generate DEMs using stereophotogrammetry?
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What is the role of Radar in remote sensing?
What is the role of Radar in remote sensing?
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What is the primary advantage of using PRISM (ALOS) and CARTOSAT-1 for generating DEMs?
What is the primary advantage of using PRISM (ALOS) and CARTOSAT-1 for generating DEMs?
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What technique is commonly used to create high-resolution DEMs from UAV images?
What technique is commonly used to create high-resolution DEMs from UAV images?
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Which of the following is NOT a type of sensor that can be mounted on UAVs?
Which of the following is NOT a type of sensor that can be mounted on UAVs?
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Laser altimetry is primarily used for what function?
Laser altimetry is primarily used for what function?
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Which statement accurately describes LiDAR aerial surveys?
Which statement accurately describes LiDAR aerial surveys?
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Which platform was used to produce the quasi-global ASTER GDEM?
Which platform was used to produce the quasi-global ASTER GDEM?
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What is a key characteristic of stereo pairs used in remote sensing?
What is a key characteristic of stereo pairs used in remote sensing?
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What is often the cost of generating DEMs using PRISM and CARTOSAT-1?
What is often the cost of generating DEMs using PRISM and CARTOSAT-1?
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What principle underlies airborne optical sensing of bathymetry?
What principle underlies airborne optical sensing of bathymetry?
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What kind of water conditions are required for airborne optical sensing methods?
What kind of water conditions are required for airborne optical sensing methods?
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How is water depth determined in the echo sounding method?
How is water depth determined in the echo sounding method?
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Which of the following is NOT a type of echo sounding system?
Which of the following is NOT a type of echo sounding system?
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What can be created using airborne optical sensing approaches?
What can be created using airborne optical sensing approaches?
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What is the main purpose of using stereo pairs of images in photogrammetry?
What is the main purpose of using stereo pairs of images in photogrammetry?
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Which of these satellite platforms can be used to generate Digital Elevation Models (DEMs)?
Which of these satellite platforms can be used to generate Digital Elevation Models (DEMs)?
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What is the primary resolution of the ASTER VNIR sensor used for generating DEMs?
What is the primary resolution of the ASTER VNIR sensor used for generating DEMs?
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How does the vertical accuracy of DEMs generated from ASTER images compare to the pixel resolution?
How does the vertical accuracy of DEMs generated from ASTER images compare to the pixel resolution?
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What limitation is associated with the use of very high resolution images like Quickbird and IKONOS for detailed studies?
What limitation is associated with the use of very high resolution images like Quickbird and IKONOS for detailed studies?
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What does the term 'stereo correlations' refer to in photogrammetry?
What does the term 'stereo correlations' refer to in photogrammetry?
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Which statement about the resolution of the IKONOS satellite is true?
Which statement about the resolution of the IKONOS satellite is true?
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What is the purpose of reconstructing the geometric parameters in the context of stereo photography?
What is the purpose of reconstructing the geometric parameters in the context of stereo photography?
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What does LiDAR primarily generate from point measurements?
What does LiDAR primarily generate from point measurements?
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What is the attainable vertical coordinate accuracy of LiDAR for well-defined target surfaces?
What is the attainable vertical coordinate accuracy of LiDAR for well-defined target surfaces?
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Which method describes the SAR technique that utilizes phase-difference measurements?
Which method describes the SAR technique that utilizes phase-difference measurements?
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What are the four techniques that can be applied to produce DEMs using SAR?
What are the four techniques that can be applied to produce DEMs using SAR?
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Which type of SAR mode uses two flights over the target area?
Which type of SAR mode uses two flights over the target area?
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In the context of LiDAR, what does a Digital Terrain Model (DTM) represent?
In the context of LiDAR, what does a Digital Terrain Model (DTM) represent?
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What is the average cost range of LiDAR per square kilometer?
What is the average cost range of LiDAR per square kilometer?
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What is one of the common uses of SAR-based DEMs?
What is one of the common uses of SAR-based DEMs?
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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 ______.
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The optical EM spectrum includes visible light, near infrared, and ______ infrared radiations.
The optical EM spectrum includes visible light, near infrared, and ______ infrared radiations.
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Radar Altimetry and Lidar are examples of ______ remote sensing methods.
Radar Altimetry and Lidar are examples of ______ remote sensing methods.
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Stereophotogrammetry is utilized to produce DEMs from stereo pairs obtained by ______ remote sensing.
Stereophotogrammetry is utilized 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 ______.
The primary advantage of stereo imagery is the ability to extract geographic features in ______.
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In stereophotogrammetry, an operator uses a stereoplotter to move two dots together until they appear as one lying just at the ______ of the ground.
In stereophotogrammetry, an operator uses a stereoplotter to move two dots together until they appear as one lying just at the ______ of the ground.
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The automated method in stereophotogrammetry calculates the ______ displacement of a large number of points.
The automated method in stereophotogrammetry calculates the ______ displacement of a large number of points.
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Lidar (light detection and ranging) uses active sensors with ______ electromagnetic energy.
Lidar (light detection and ranging) uses active sensors with ______ electromagnetic energy.
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A stereopair of radar image coordinates can be computed using stereo __________.
A stereopair of radar image coordinates can be computed using stereo __________.
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Automated photogrammetric generation of __________ can be done by processing digitized stereo pairs.
Automated photogrammetric generation of __________ can be done by processing digitized stereo pairs.
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Various optical satellite sensors like Quickbird and IKONOS have resolutions ranging from __________ to 5 m.
Various optical satellite sensors like Quickbird and IKONOS have resolutions ranging from __________ to 5 m.
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The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) carries __________ channels.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) carries __________ channels.
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The VNIR sensor allows generation of DEMs with a pixel resolution of __________ m.
The VNIR sensor allows generation of DEMs with a pixel resolution of __________ m.
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DEMs generated from ASTER images have a vertical accuracy less than __________ meters.
DEMs generated from ASTER images have a vertical accuracy less than __________ meters.
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Satellite stereo images from platforms like SPOT and __________ can be utilized to generate DEMs.
Satellite stereo images from platforms like SPOT and __________ can be utilized to generate DEMs.
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High acquisition costs of __________ images hinder their application in detailed studies.
High acquisition costs of __________ images hinder their application in detailed studies.
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The __________ sensor has been utilized for generating DEMs with various resolutions using stereo images.
The __________ sensor has been utilized for generating DEMs with various resolutions using stereo images.
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The pixel resolution of ASTER images ranges from 15m to __________ m.
The pixel resolution of ASTER images ranges from 15m to __________ m.
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PRISM (ALOS) and CARTOSAT-1 have a resolution of ______ m.
PRISM (ALOS) and CARTOSAT-1 have a resolution of ______ m.
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UAVs are increasingly used for ______ sensing.
UAVs are increasingly used for ______ sensing.
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Laser altimetry, also known as ______, uses laser pulses to measure distances.
Laser altimetry, also known as ______, uses laser pulses to measure distances.
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Demonstrated by UAV photogrammetry, a key advantage is its ______ alternative to traditional methods.
Demonstrated by UAV photogrammetry, a key advantage is its ______ alternative to traditional methods.
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DTM-based solutions from LiDAR can be applied to ______-scale mapping.
DTM-based solutions from LiDAR can be applied to ______-scale mapping.
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Satellite laser altimetry contributes to the generation of Digital Elevation ______.
Satellite laser altimetry contributes to the generation of Digital Elevation ______.
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Aerial surveys using LiDAR can create high-resolution DEMs of both land surfaces and the ______.
Aerial surveys using LiDAR can create high-resolution DEMs of both land surfaces and the ______.
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Images from the Terra satellite contributed to the production of the quasi-global ______ GDEM.
Images from the Terra satellite contributed to the production of the quasi-global ______ GDEM.
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UAVs can be equipped with various sensors, such as ______ band cameras.
UAVs can be equipped with various sensors, such as ______ band cameras.
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Laser altimetry emits laser pulses that are reflected from the ______ surface.
Laser altimetry emits laser pulses that are reflected from the ______ surface.
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LiDAR point measurements render Digital Surface Models (DSM), which contains information on all objects of the Earth’s surface, including buildings and ______.
LiDAR point measurements render Digital Surface Models (DSM), which contains information on all objects of the Earth’s surface, including buildings and ______.
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The large one-pass spaceborne SAR interferometer was based on two similar radar satellites, TerraSAR-X and ______.
The large one-pass spaceborne SAR interferometer was based on two similar radar satellites, TerraSAR-X and ______.
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Satellite radar altimetry is used to calculate heights on the earth by sending out short pulses of ______ energy.
Satellite radar altimetry is used to calculate heights on the earth by sending out short pulses of ______ energy.
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Through sophisticated algorithms and final manual editing, the landscape elements are removed and a Digital ______ Model (DTM) is generated.
Through sophisticated algorithms and final manual editing, the landscape elements are removed and a Digital ______ Model (DTM) is generated.
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SAR is a group of active remote sensing techniques where the SAR antenna transmits electromagnetic radiation at ______ frequencies.
SAR is a group of active remote sensing techniques where the SAR antenna transmits electromagnetic radiation at ______ frequencies.
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An example of a mission that carries a radar altimeter is the Jason-2 Ocean Surface Topography ______.
An example of a mission that carries a radar altimeter is the Jason-2 Ocean Surface Topography ______.
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SAR-based DEMs are utilized in medium- and small-scale mapping of large ______.
SAR-based DEMs are utilized in medium- and small-scale mapping of large ______.
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Applications of satellite radar altimetry include calculating the height of land, ocean, and ______ water bodies.
Applications of satellite radar altimetry include calculating the height of land, ocean, and ______ water bodies.
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Synthetic Aperture Radar Interferometry (InSAR) is mostly used for detecting changes in ______ heights.
Synthetic Aperture Radar Interferometry (InSAR) is mostly used for detecting changes in ______ heights.
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InSAR utilizes phase-difference measurements derived from two radar images, which can be obtained by one-pass or ______ collection modes.
InSAR utilizes phase-difference measurements derived from two radar images, which can be obtained by one-pass or ______ collection modes.
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The InSAR technique was applied in the Shuttle Radar Topography Mission to prepare several Global DEMs with different ______.
The InSAR technique was applied in the Shuttle Radar Topography Mission to prepare several Global DEMs with different ______.
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The average costs of LiDAR range from ______ to 800 US$/km2 depending on the required point density.
The average costs of LiDAR range from ______ to 800 US$/km2 depending on the required point density.
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To produce DEMs, four SAR techniques can be applied: interferometry, stereoscopy, ______, and clinometry.
To produce DEMs, four SAR techniques can be applied: interferometry, stereoscopy, ______, and clinometry.
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The one-pass mode of InSAR utilizes two SARs, but only one of them, the primary antenna, ______ pulses.
The one-pass mode of InSAR utilizes two SARs, but only one of them, the primary antenna, ______ pulses.
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The attainable elevation accuracy with LiDAR can be in the order of ______ cm for well-defined target surfaces.
The attainable elevation accuracy with LiDAR can be in the order of ______ cm for well-defined target surfaces.
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Study Notes
Remote Sensing Methods
- Active and passive sensors are used in remote sensing, mounted on airborne platforms (planes, drones) or spaceborne platforms (satellites, shuttles).
- The electromagnetic (EM) spectrum utilized includes optical (visible, near infrared, shortwave infrared) and microwave.
- Optical imageries from overlapping images are processed for DEM generation through stereo photogrammetry; radar imageries also support this process.
- Non-imaging methods such as Radar Altimetry and LiDAR involve active sensors for elevation measurements.
Stereophotogrammetry Method
- Stereophotogrammetry uses stereo pairs from optical remote sensing to generate DEMs.
- Manual stereophotogrammetry requires operators to visually match images through a stereoplotter; automated methods calculate parallax displacement using instruments.
- It enables 3D extraction of geographic features like buildings and roads.
- DEM generation can use satellite images from platforms like SPOT, QuickBird, and ALOS, with varying resolutions.
Satellite Sensors for DEM Generation
- Optical satellite sensors include Quickbird (2-5 m), Pleiades (1 m), WorldView2, and ASTER (15-30 m).
- ASTER, launched in 1999, provides 30 m resolution free DEM data via Earthdata web service.
- High-resolution satellite data is costly; PRISM (ALOS) offers a cheaper alternative with 2.5 m resolution at lower costs.
UAVs in Remote Sensing
- Unmanned Aerial Vehicles (UAVs) are increasingly utilized, equipped with various sensors like visible band and laser scanners.
- UAVs present a cost-effective alternative for high- and very high-resolution DEMs.
LiDAR Method
- LiDAR (Light Detection and Ranging) uses active sensors to emit laser pulses and measure reflected light for elevation calculation.
- Available in aerial and satellite forms, LiDAR generates high-resolution DEMs, including DSMs and DTMs.
- LiDAR provides high accuracy, typically around 3 cm, with costs ranging from 300to300 to 300to800 per km².
Synthetic Aperture Radar (SAR) Method
- SAR is an active remote sensing technique using microwave frequencies to produce DEMs.
- Techniques include interferometry, stereoscopy, polarimetry, and clinometry; interferometric SAR (InSAR) is most widely used.
- InSAR was essential for the Shuttle Radar Topography Mission (SRTM), producing various resolution global DEMs (up to 1” resolution).
Airborne Optical Sensing for Bathymetry
- Uses passive remote sensing to estimate water depth from radiative energy reflected by the water column.
- Effective only in clear waters for creating DEMs of shallow seafloors, aiding navigation safety.
Echo Sounding Method
- A hydrographic sonar technique for determining underwater topography by transmitting sound pulses and measuring time lag.
- Types of echo sounding include single-beam, multibeam, and side-scan systems to accurately assess water depth.
Remote Sensing Methods
- Utilizes active and passive sensors on airborne (planes, drones) and spaceborne platforms (satellites).
- Light and microwave portions of the electromagnetic spectrum are employed.
- Optical methodologies involve visible light, near infrared, and shortwave infrared radiations for imagery acquisition.
- Radar imagery uses microwave EM for elevation data generation.
- Non-imaging remote sensing includes Radar Altimetry and Lidar.
Stereophotogrammetry Method
- Classical approach for producing Digital Elevation Models (DEMs) using stereo image pairs garnered from optical remote sensing.
- Can be performed manually (with stereoplotter) or automatically (using instruments for correlation).
- Stereo imagery allows 3D feature extraction, useful for analyzing geographic elements like roads and structures.
- Satellite stereo images can come from platforms like SPOT, Ikonos, and ALOS, with various sensors offering different resolutions.
Satellite Sensors for DEM Generation
- High-resolution sensors: Quickbird (2-5 m), Pleiades (1 m), WorldView (1-2 m).
- ASTER provides medium resolution (30 m) free DEM data with accuracy under 20 m from 15 m resolution images.
- Recent technologies reduce costs of high-resolution data collection to less than $10/km².
Unmanned Aerial Vehicles (UAVs)
- Drones increasingly utilized for remote sensing, providing various sensor options (visible, multispectral, thermal).
- Offer a cost-effective alternative to traditional aerial surveying methods.
Laser Altimetry (LiDAR) Method
- Active remote sensing technique using laser pulses for terrain measurement.
- Produces high-resolution Digital Surface Models (DSM) and Digital Terrain Models (DTM) through point cloud data.
- Vertical accuracy of LiDAR can reach 3 cm.
- Cost of LiDAR varies from $300 to $800/km² based on point density requirements.
Synthetic Aperture Radar (SAR) Method
- Active technique transmitting microwave radiation for DEM generation.
- SAR operates on moving platforms and produces medium resolution topography maps.
- Common techniques include interferometry, stereoscopy, polarimetry, and clinometry.
- InSAR utilized for notable missions like the Shuttle Radar Topography Mission (SRTM) to generate various global DEMs.
Satellite Radar Altimetry Method
- Measures Earth's heights with microwave energy pulses, correcting for atmospheric variations.
- Example: Jason-2 mission uses advanced radar altimeter for ocean surface monitoring and marine gravity analysis.
- Effective in capturing land and water height data, addressing challenges such as sparse ship track data for submarine topography.
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Description
Explore the concepts surrounding Digital Elevation Models (DEMs) as covered in Chapter 2 of CE 797. This quiz will focus on the applications of DEMs in GIS and their integration with remote sensing methods. Test your understanding of key principles and techniques in civil engineering related to digital elevation.
