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Airborne Laser

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Norbert Pfeifer – One of the best experts on this subject based on the ideXlab platform.

  • tree species classification based on full waveform Airborne Laser scanning data
    , 2009
    Co-Authors: Markus Hollaus, Norbert Pfeifer, Werner Mücke, Bernhard Hofle, Wouter Dorigo, Wolfgang Wagner, C Bauerhansl, B Regner
    Abstract:

    Airborne Laser scanning is an evolving operational measurement technique for deriving forest parameters. The objective of the current study was to analyze the potential of full-waveform Airborne Laser scanning for tree species classification of a mixed woodland. The quantities used were the echo width, backscatter cross section, as well as the distribution of the echoes in vertical direction. Based on segmented tree crowns the mean backscatter cross section of all echoes above the 50 th height percentile was computed. Additionally, the canopy density, describing the ratio of the number of all echoes above the 50 th height percentile and the total number of echoes, was used for a knowledge-based classification of coniferous and deciduous trees. The achieved overall accuracy was 83%. Furthermore, the standard deviation of the echo widths per crown segment was applied for a separation of spruce and larch. An overall accuracy of the classified tree species red beech, larch and spruce of 75% was obtained. The presented results show that combining geometric information and backscattering properties of full-waveform Airborne Laser scanning data has a high potential for tree species classification.

  • extraction of building footprints from Airborne Laser scanning comparison and validation techniques
    Urban Remote Sensing Joint Event, 2007
    Co-Authors: Norbert Pfeifer, Martin Rutzinger, Franz Rottensteiner, W Muecke, Markus Hollaus
    Abstract:

    Many applications in urban planning and analysis require the position and extent of buildings, the so-called building footprint. Cadastral maps acquired by ground based surveying are often not up-to-date or may not be available at all. Airborne Laser scanning, on the other hand, offers the possibility to detect the roof outlines in an automated manner. This subject has been researched in the previous years, but a final comparison of the quality of these algorithms has not been performed. Additionally, the methods for assessing the quality of building footprint extraction should consider the special characteristics of Airborne Laser scanning data. This paper gives an overview of the algorithms developed for the task of house detection from Airborne Laser scanning and evaluates two algorithms experimentally. The methods of quality assessment are discussed and next to the standard method of pixel based comparison the object based comparison is studied, providing more insight.

  • Extraction of building footprints from Airborne Laser scanning: Comparison and validation techniques (Invited Paper)
    , 2007
    Co-Authors: Norbert Pfeifer, Markus Hollaus, Martin Rutzinger, Franz Rottensteiner, W Muecke, Christian Doppler
    Abstract:

    Many applications in urban planning and analysis require the position and extent of buildings, the so-called building footprint. Cadastral maps acquired by ground based surveying are often not up-to-date or may not be available at all. Airborne Laser scanning, on the other hand, offers the possibility to detect the roof outlines in an automated manner. This subject has been researched in the previous years, but a final comparison of the quality of these algorithms has not been performed. Additionally, the methods for assessing the quality of building footprint extraction should consider the special characteristics of Airborne Laser scanning data. This paper gives an overview of the algorithms developed for the task of house detection from Airborne Laser scanning and evaluates two algorithms experimentally. The methods of quality assessment are discussed and next to the standard method of pixel based comparison the object based comparison is studied, providing more insight.

Wolfgang Wagner – One of the best experts on this subject based on the ideXlab platform.

  • radiometric calibration of small footprint full waveform Airborne Laser scanner measurements basic physical concepts
    Isprs Journal of Photogrammetry and Remote Sensing, 2010
    Co-Authors: Wolfgang Wagner
    Abstract:

    Abstract Small-footprint (0.2–2 m) Airborne Laser scanners are lidar instruments originally developed for topographic mapping. While the first Airborne Laser scanners only allowed determining the range from the sensor to the target, the latest sensor generation records the complete echo waveform. The waveform provides important information about the backscattering properties of the observed targets and may be useful for geophysical parameter retrieval and advanced geometric modelling. However, to fully utilise the potential of the waveform measurements in applications, it is necessary to perform a radiometric calibration. As there are not yet calibration standards, this paper reviews some basic physical concepts commonly used by the remote sensing community for modelling scattering and reflection processes. Based purely on theoretical arguments it is recommended to use the backscattering coefficient γ , which is the backscatter cross-section normalised relative to the Laser footprint area, for the radiometric calibration of small-footprint full-waveform Airborne Laser scanners. The presented concepts are, with some limitations, also applicable to conventional Airborne Laser scanners that measure the range and intensity of multiple echoes.

  • tree species classification based on full waveform Airborne Laser scanning data
    , 2009
    Co-Authors: Markus Hollaus, Norbert Pfeifer, Werner Mücke, Bernhard Hofle, Wouter Dorigo, Wolfgang Wagner, C Bauerhansl, B Regner
    Abstract:

    Airborne Laser scanning is an evolving operational measurement technique for deriving forest parameters. The objective of the current study was to analyze the potential of full-waveform Airborne Laser scanning for tree species classification of a mixed woodland. The quantities used were the echo width, backscatter cross section, as well as the distribution of the echoes in vertical direction. Based on segmented tree crowns the mean backscatter cross section of all echoes above the 50 th height percentile was computed. Additionally, the canopy density, describing the ratio of the number of all echoes above the 50 th height percentile and the total number of echoes, was used for a knowledge-based classification of coniferous and deciduous trees. The achieved overall accuracy was 83%. Furthermore, the standard deviation of the echo widths per crown segment was applied for a separation of spruce and larch. An overall accuracy of the classified tree species red beech, larch and spruce of 75% was obtained. The presented results show that combining geometric information and backscattering properties of full-waveform Airborne Laser scanning data has a high potential for tree species classification.

M. Cocard – One of the best experts on this subject based on the ideXlab platform.

  • Airborne Laser altimetry in the Ionian Sea, Greece
    , 2002
    Co-Authors: M. Cocard, Alain Geiger, H.-g. Kahle, George Veis
    Abstract:

    Airborne Laser techniques have evolved during the last years and have been tested in several pilot projects which cover a wide range of geodetic applications. In this project, Airborne Laser altimetry was used to determine the sea level in coastal areas of Greece, and to connect satellite radar altimetry results over the deep sea with tide gauge stations at the coast. Because Airborne Laser altimetry is capable to provide sea surface heights at the decimeter to centimeter level, it allows for an independent validation of spaceborne radar altimetry results. Airborne Laser data acquired along densely spaced tracks of a total of 30-h flight time were used to determine instantaneous sea surface heights of the Ionian Sea, Greece. Differential GPS and inertial platform data were utilized as ancillary information for the purpose of ensuring a precise trajectography of the aircraft. Emphasis was put on the assessment of errors and the reduction of the raw data to mean sea level by crossover analysis and the incorporation of tidal predictions. The Airborne Laser data yield a high-resolution sea surface over the coastal areas of the Ionian Sea. The most prominent feature is a steep gradient of the sea surface amounting to 15 m over a distance of 150 km. This slope can be followed all along the bathymetric relief between the Hellenic Arc and Hellenic Trench.

  • Airborne Laser altimetry in the Ionian Sea, Greece
    Global and Planetary Change, 2002
    Co-Authors: M. Cocard
    Abstract:

    Airborne Laser techniques have evolved during the last years and have been tested in several pilot projects which cover a wide range of geodetic applications. In this project, Airborne Laser altimetry was used to determine the sea level in coastal areas of Greece, and to connect satellite radar altimetry results over the deep sea with tide gauge stations at the coast. Because Airborne Laser altimetry is capable to provide sea surface heights at the decimeter to centimeter level, it allows for an independent validation of spaceborne radar altimetry results. Airborne Laser data acquired along densely spaced tracks of a total of 30-h flight time were used to determine instantaneous sea surface heights of the Ionian Sea, Greece. Differential GPS and inertial platform data were utilized as ancillary information for the purpose of ensuring a precise trajectography of the aircraft. Emphasis was put on the assessment of errors and the reduction of the raw data to mean sea level by crossover analysis and the incorporation of tidal predictions. The Airborne Laser data yield a high-resolution sea surface over the coastal areas of the Ionian Sea. The most prominent feature is a steep gradient of the sea surface amounting to 15 m over a distance of 150 km. This slope can be followed all along the bathymetric relief between the Hellenic Arc and Hellenic Trench. (C) 2002 Elsevier Science B.V. All rights reserved

Jerry C. Ritchie – One of the best experts on this subject based on the ideXlab platform.

  • Remote sensing applications to hydrology: Airborne Laser altimeters
    Hydrological Sciences Journal, 1996
    Co-Authors: Jerry C. Ritchie
    Abstract:

    Shortly after the development of the first Laser instrument in 1960, studies began on using Laser distancing technology from Airborne platforms to measure surface features on the landscape. Airborne Laser altimeter studies in the 1960s and 1970s were used to measure terrain features and sea ice roughness. Research in the 1980s and 1990s has shown that Airborne Laser measurements can be used to measure directly topography, stream channel cross sections, gully cross sections, soil surface roughness, and vegetation canopy height, cover and distribution. These Laser measurements can be used to estimate forest biomass and volume, aerodynamic roughness and leaf area indices. Airborne Laser altimeters provide quick and accurate measurements for evaluating changes in land surface features and can be an additional tool in the arsenal of remote sensing equipment used to understand watershed properties and to develop plans to manage water resources.

  • Airborne Laser altimeter measurements of landscape topography
    Remote Sensing of Environment, 1995
    Co-Authors: Jerry C. Ritchie
    Abstract:

    Abstract Measurements of topography can provide a wealth of information on landscape properties for managing hydrologic and geologic systems and conserving natural and agricultural resources. This article discusses the application of an Airborne Laser altimeter to measure topography and other landscape surface properties. The Airborne Laser altimeter makes 4000 measurements per second with a vertical recording resolution of 5 cm. Data are collected digitally with a personal computer. A video camera, borehole sighted with the Laser, records an image for locating flight lines. GPS data are used to locate flight line positions on the landscape. Laser data were used to measure vegetation canopy topography, height, cover, and distribution and to measure microtopography of the land surface and gullies with depths of 15–20 cm. Macrotopography of landscape profiles for segments up to 4 km were in agreement with available topographic maps but provided more detail. Larger gullies with and without vegetation, and stream channel cross sections and their associated floodplains have also been measured and reported in other publications. Landscape segments for any length could be measured for either micro- or macrotopography. Airborne Laser altimeter measurements of landscape profiles can provide detailed information on landscape properties or specific needs that will allow better decisions on the design and location of structures (i.e., roads, pipe, and power lines) and for improving the management and conservation of natural and agricultural landscapes.

  • MEASURING CANOPY STRUCTURE WITH AN Airborne Laser ALTIMETER
    Transactions of the ASAE, 1993
    Co-Authors: Jerry C. Ritchie, D. L. Evans, D. Jacobs, James H. Everitt, Mark A. Weltz
    Abstract:

    Quantification of vegetation patterns and properties is needed to determine their role on the landscape and to develop management plans to conserve our natural resources. Quantifying vegetation patterns from the ground, or by using aerial photography or satellite imagery is difficult, time consuming, and often expensive. Digital data from an Airborne Laser altimeter offer an alternative method to quantify selected vegetation properties and patterns of forest and range vegetation. Airborne Laser data found canopy heights varied from 2 to 6 m within even-aged pine forests. Maximum canopy heights measured with the Laser altimeter were significantly correlated to measurements made with ground-based methods. Canopy shape could be used to distinguish deciduous and evergreen trees. In rangeland areas, vegetation heights, spatial patterns, and canopy cover measured with the Laser altimeter were significantly related with field measurements. These studies demonstrate the potential of Airborne Laser data to measure canopy structure and properties for large areas quickly and quantitatively.

H.-g. Kahle – One of the best experts on this subject based on the ideXlab platform.

  • Some examples of European activities in Airborne Laser techniques and an application in glaciology
    Journal of Geodynamics, 2002
    Co-Authors: Etienne Favey, Aloysius Wehr, A Geiger, H.-g. Kahle
    Abstract:

    Abstract Airborne Laser Altimetry (ALA) has experienced a rapid increase in popularity as a method serving a wide range of applications in Remote Sensing, Geodesy, Geophysics and Geodynamics. Besides the ‘traditional’ approach of using Laser scanning solely as a supplement for photogrammetry in acquiring digital terrain models, ALA has also been applied to various geoscience research problems. After a short overview of Airborne Laser altimetry activities in Europe, an application of Airborne Laser scanning dedicated to Alpine Glaciology is presented.

  • Airborne Laser altimetry in the Ionian Sea, Greece
    , 2002
    Co-Authors: M. Cocard, Alain Geiger, H.-g. Kahle, George Veis
    Abstract:

    Airborne Laser techniques have evolved during the last years and have been tested in several pilot projects which cover a wide range of geodetic applications. In this project, Airborne Laser altimetry was used to determine the sea level in coastal areas of Greece, and to connect satellite radar altimetry results over the deep sea with tide gauge stations at the coast. Because Airborne Laser altimetry is capable to provide sea surface heights at the decimeter to centimeter level, it allows for an independent validation of spaceborne radar altimetry results. Airborne Laser data acquired along densely spaced tracks of a total of 30-h flight time were used to determine instantaneous sea surface heights of the Ionian Sea, Greece. Differential GPS and inertial platform data were utilized as ancillary information for the purpose of ensuring a precise trajectography of the aircraft. Emphasis was put on the assessment of errors and the reduction of the raw data to mean sea level by crossover analysis and the incorporation of tidal predictions. The Airborne Laser data yield a high-resolution sea surface over the coastal areas of the Ionian Sea. The most prominent feature is a steep gradient of the sea surface amounting to 15 m over a distance of 150 km. This slope can be followed all along the bathymetric relief between the Hellenic Arc and Hellenic Trench.