CE 797: Digital Elevation Models Chapter 2
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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.

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

Stereophotogrammetry is the classical way to produce DEMs from stereo pairs obtained by ______ remote sensing.

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

The primary advantage of stereo imagery is the ability to extract geographic features in ______.

<p>3D</p> Signup and view all the answers

In the manual method of stereophotogrammetry, an operator uses a ______ to view a pair of stereophotos.

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

The automated method of stereophotogrammetry calculates the ______ displacement of points.

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

The PRISM and CARTOSAT-1 satellites provide high resolution data with a resolution of ______ meters.

<p>2.5</p> Signup and view all the answers

UAVs can be equipped with various types of sensors including visible band, multispectral, thermal cameras, and ______.

<p>laser scanners</p> Signup and view all the answers

Laser altimetry, also known as ______, is a technique used for active remote sensing.

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

The returned laser pulses in LiDAR allow for the calculation of the distance from the ground surface considering the speed of ______.

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

Satellite laser altimetry is widely used for generating ______.

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

UAV photogrammetry offers a low-cost alternative to manned aerial ______.

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

LiDAR aerial surveys can create high-resolution DEMs down to ______ meters in clear waters.

<p>70</p> Signup and view all the answers

The quasi-global ASTER GDEM was produced by processing stereo pairs from the ______ satellite.

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

Costs for producing DEMs from PRISM and CARTOSAT-1 are lower than ______ USD per square kilometer.

<p>10</p> Signup and view all the answers

Recent advancements have allowed UAVs to be used increasingly for ______ sensing.

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

Current bathymetric charts are inadequate because only a small fraction of the seafloor has been ______.

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

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 ______.

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

Echo sounding techniques are used to determine the distance between the water surface and underwater ______.

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

The depth of water in echo sounding is determined from the time lag between the emission and return of a ______.

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

Common single-beam echo sounders transmit a single beam oriented toward the vessel’s ______.

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

More detailed DEMs are derived using ______.

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

LiDAR point measurements will render Digital Surface Models (DSM), which contains information on all objects including ______.

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

Through sophisticated algorithms, landscape elements are removed to generate a Digital ______ Model (DTM).

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

The average costs of LiDAR range from ______ to 800 US$/km2.

<p>300</p> Signup and view all the answers

SAR is a group of active remote sensing techniques that transmits electromagnetic radiation at ______ frequencies.

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

To produce DEMs using SAR, techniques such as interferometry and ______ using stereo pairs of radar images can be applied.

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

The most common InSAR techniques utilize phase-difference measurements derived from ______ radar images.

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

The InSAR technique was applied in the Shuttle Radar Topography Mission to prepare ______ Global DEMs.

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

These resolutions correspond to about 1 km, 500 m, 100 m, and ______ m respectively.

<p>30</p> Signup and view all the answers

SAR-based DEMs are utilized in medium- and small-scale mapping of ______ areas.

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

The large one-pass spaceborne SAR interferometer is based on two similar radar satellites, TerraSAR-X and ______.

<p>TanDEM-X</p> Signup and view all the answers

DEMs can be derived using radar satellites such as RADARSAT, TerraSAR-X, and ______.

<p>ALOS PALSAR</p> Signup and view all the answers

Synthetic Aperture Radar Interferometry (InSAR) is primarily used for detecting changes in topographic heights related to ______ geological processes.

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

Satellite radar altimetry measures height by sending out short pulses of ______ energy.

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

One application of satellite radar altimetry is calculating the height of ocean and ______.

<p>inland water bodies</p> Signup and view all the answers

The Jason-2 Ocean Surface Topography Mission, launched in 2008, carries the Poseidon-3 Radar ______.

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

In satellite radar altimetry, the received back echoes or reflections are measured to correct for potential error sources such as changes in ______.

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

Satellite radar altimeters are also used to reveal marine gravity ______.

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

Ship track echo-sounding data are often too sparse to fully define submarine ______.

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

To accurately determine the satellite’s position in space, the Jason-2 mission employs advanced ______.

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

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.

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