XXII ISPRS Congress 2012: Technical Commission VII

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Multivolume work

Persistent identifier:: 1663813779

Title:: XXII ISPRS Congress 2012

Sub title:: Melbourne, Australia, 25 August-1 September 2012

Year of publication:: 2013

Place of publication:: Red Hook, NY

Publisher of the original:: Curran Associates, Inc.

Identifier (digital):: 1663813779

Language:: English

Additional Notes:: Kongress-Thema: Imaging a sustainable future

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Document type:: Multivolume work

Volume

Persistent identifier:: 1663821976

Title:: Technical Commission VII

Scope:: 546 Seiten

Year of publication:: 2013

Place of publication:: Red Hook, NY

Publisher of the original:: Curran Associates, Inc.

Identifier (digital):: 1663821976

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(39,B7)

Language:: English

Additional Notes:: Erscheinungsdatum des Originals ist ermittelt.; Literaturangaben

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2019

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: [VII/7, III/2, V/3: WAVEFORM LIDAR FOR REMOTE SENSING]

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: WAVEFORM ANALYSIS FOR THE EXTRACTION OF POST-FIRE VEGETATION CHARACTERISTICS F. Pirotti, A. Guarnieri, A. Vettore

Document type:: Multivolume work

Structure type:: Chapter

International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia WAVEFORM ANALYSIS FOR THE EXTRACTION OF POST-FIRE VEGETATION CHARACTERISTICS F. Pirotti® *, A. Guarnieri“, A. Vettore® * CIRGEO, Interdepartmental Center for Research in Geomatics, 35020 Legnaro (PD) - Italy - (francesco.pirotti, alberto.guarnieri, antonio. vettore)@unipd.it Commission VII, WG VI/4 KEY WORDS: Full Waveform laser scanner, vegetation height distribution, airborne lidar survey ABSTRACT: Full-waveform is becoming increasingly available in today's LiDAR systems and the analysis of the full return signal can provide additional information on the reflecting surfaces. In this paper we present the results of an assessment on full-waveform analysis, as opposed to the more classic discrete return analysis, for discerning vegetation cover classes related to post-fire renovation. In the spring of 2011 an OPTECH ALTM sensor was used to survey an Alpine area of almost 20 km? in the north of Italy. A forest fire event several years ago burned large patches of vegetation for a total of about 1.5 km? . The renovation process in the area is varied because of the different interventions ranging from no intervention to the application of re-forestation techniques to accelerate the process of re-establishing protection forest. The LiDAR data was used to divide the study site into areas with different conditions in terms of re-establishment of the natural vegetation condition. The LiDAR survey provided both the full-waveform data in Optech’s CSD+DGT (corrected sensor data) and NDF+IDX (digitizer data with index file) formats, and the discrete return in the LAS format. The method applied to the full-waveform uses canopy volume profiles obtained by modelling, whereas the method applied to discrete return uses point geometry and density indexes. The results of these two methods are assessed by ground truth obtained from sampling and comparison shows that the added information from the full-waveform does give a significant better discrimination of the vegetation cover classes. 1. INTRODUCTION Ranges from multiple returns are recorded depending on the sensor; two echoes (first and last) or multiple echoes (up to Airborne LiDAR (or Airborne Laser Scanning - ALS) in the past eight) can be recorded. Each sensor has a range resolution which ten years has seen rapid growth in both sensor technology and describes the minimum distance required between objects, for fields of application. Research on laser profilers started in the separating two return echoes. This measure depends on the late nineties and a lot of interest was given to the forestry outgoing pulse duration and the group velocity, some ALS environment because of the ability of the laser pulse to penetrate systems have a dead zone of up to 3 m (Wagner et al., 2008). canopy, returning ground hits, which are precious for digital Discrete-return sensors process the return echo waveform using terrain models (DTMs) extraction (Carson et al., 2004). Studies fast yet simple algorithms like the Constant Fraction over the rate of penetration show that typical coniferous and Discriminator criteria for defining a threshold for the deciduous forests allow 20-40% of the laser pulses to return identification of significant energy peaks (Thiel and Wehr, ground hits in leaf-on conditions and as much as 70% in leaf-off 2006). conditions (Ackermann, 1999). This can occur because the size of the diffraction cone (Mallet and Bretar, 2009) can vary froma Off-line processing of the waveform requires recording the full few centimeters up to one/two meters; thus the canopy area that waveform of the return echo by means of a digitizer which is illuminated is large enough to have a significant amount of samples the return energy at certain time intervals usually from gaps which allow part of the laser energy to pass without getting ^ one to several nanoseconds. To this day a significant amount of reflected by leaves of branches, all the way to the ground, which tests have been conducted on waveform data from spaceborne is the element which causes the last reflection. and airborne sensors. NASA's GLAS sensor, mounted on Discrete-return ALS systems provide data as 3D coordinates IceSAT satellite provided freely downloadable full waveform and intensity, commonly referred to as “point cloud”, by on-line data for several years before recent mission dismissal. The main processing of the retum laser echo. If one laser pulse gets objective was the estimation of the thickness and dynamics of reflected by different surfaces along its path, interactions of the the polar ice-sheet (Zwally et al, 2002), but its large-footprint laser with the objects cause a return signal whose characteristics (^65 m) waveform information was also used also for extracting are a mixture derived from the different optical properties of the vegetation structure (Harding and Carabajal, 2005), ground objects, the range and the incidence angle (Wagner et al., 2006). ^ cover classification (Pirotti, 2010) as well as direct canopy * Corresponding author. This is useful to know for communication with the appropriate person in cases with more than one author. 523

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