Proceedings, XXth congress: Proceedings, XXth congress

Altan, M. Orhan

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Multivolume work

Persistent identifier:: 1663674213

Title:: Proceedings, XXth congress

Sub title:: Istanbul, 12 - 23 July 2004

Year of publication:: 2004

Place of publication:: Istanbul

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 1663674213

Language:: English

Additional Notes:: Erscheinungsdatum des Originals ist aus dem Copyrightjahr ermittelt.; Auch bezeichnet als XXth International Congress for Photogrammetry and Remote Sensing

Editor:: Altan, M. Orhan

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing, Commission Primary Data Acquisition

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing, Commission Primary Data Acquisition

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing, Commission Primary Data Acquisition

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing, Commission Primary Data Acquisition

Document type:: Multivolume work

Volume

Persistent identifier:: 166368779X

Title:: Proceedings, XXth congress

Scope:: IV, 226 Seiten

Year of publication:: 2004

Place of publication:: Istanbul

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 166368779X

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(35,B8)

Language:: English

Additional Notes:: Erscheinungsdatum des Originals ist aus dem Copyrightjahr ermittelt.

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

Editor:: Altan, M. Orhan

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; 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:: QUALITY ASSESSMENT OF GLOBAL MODIS LAI PRODUCT FOR THE REGIONAL SCALE APPLICATIONS Sun-Hwa Kim and Kyu-Sung Lee

Document type:: Multivolume work

Structure type:: Chapter

International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004 Field LAI measurements Although the accurate measurement of LAT is crucial to relate the satellite observed surface reflectance, it is often difficult to obtain reliable ground-truth of LAI. Field measurement of LAI can be divided into two major approaches of direct and indirect methods (Chen et al., 1997; Gower et al., 1999). The direct method includes destructive harvest, litterfall collection, and application of allometric equations. In recently years, several optical devices become available for the indirect measurement of LAI. The basic concept of optical LAI measurement is to invert a radiation model that describes the amount of light penetrating tree canopy as a function of leaf area and distribution. In this study, we used the Li-Cor LAI 2000 plant canopy analyzer, which is a commercial instrument to indirectly measure LAI This device estimates LAI by measuring light transmittance under the forest canopy like as other optical devices. The 30 ground plots were selected to include diverse forest types of both coniferous and natural deciduous species. Field measurements were conducted from September 15 to 17, 2003. Each plot has an area of 20%20m? and includes five subplots for LAI measurements within it. LAI was measured three times at each subplot and total of 15 measurements were averaged to obtain the LAI value for each plot. The exact locations of the 30 ground plots were obtained using a differential global positioning system (GPS). Figure 1 shows the distribution of the 30 plots within the boundary of the Kyongan River basin. Figure 1. Distribution of 30 ground plots for the field LAI measurement over Kyongan River basin Generation of reference LAI and land cover map In an attempt to validate MODIS LAI product, we have constructed a reference map of LAI surface by relating the field-measured LAI to Landsat ETM+ spectral reflectance and spectral vegetation indices. To minimize any discrepancies due 28 to the phenological variation of leaf development, the ETM+ data was captured on September 10, 2002 for this study. Although the ETM+ data acquisition was one year earlier than the field measurement, we believe that it did not cause any problem since the leaf development and the actual canopy condition between 2002 and 2003 were not much different. Figure 2 showed the overall procedure of ETM+ data to construct reference LAI surfaces using the field-measured LAI. The ETM+ data were initially geo-referenced to plane rectangular coordinate system by using a set of ground control points (GCP) obtained from the 1:5,000 scale topographic maps. To extract the surface reflectance of pixels, rather than raw digital number (DN) value, ETM+ data were further processed to reduce topographic and atmospheric effects. DN value of the original image was converted to radiance by applying sensor’s gain and bias coefficients that were obtained from image headers. We used the MODTRAN radiative transfer model for the atmospheric correction using a standard atmosphere model and atmospheric humidity and visibility that were obtained from local weather stations. Geo-Referencing i Conversion of DN to Radiance Í " Atmospheric correction i Topographic correction j Converting of Radiance to Reflectance The statistical relationship between reflectance and LAI Classification of Forest Type Applying of Multiple regression models Reference LAI map i Figure 2. Procedure of constructing a reference LAI map using Landsat ETM- and ground measured LAI Further radiometric correction was applied to reduce the illumination variation caused by topographic slope and aspect. To reduce the topographic effect, we used an empirical method that normalizes the illumination difference by applying the Minnaert's constant calculated from digital elevation model (DEM) and digital map of forest stand. Minnert's method have shown its effectiveness to correct the topographically induced radiometric distortions over the forests in Korea (Lee and Yoon, 1997). The detailed information on estimating of Minnaert constant k can be found in Lee et al. (2003). A vector map of 30 sample stands of the field LAI measurement was overlaid to the geo-referenced ETM+ reflectance data and the pixels corresponding to each plot were extracted. Due to the high spatial autocorrelation, the variation of adjacent pixels was very low to overcome the problem of the sub-pixel error distance of the geometric registration. Initial approach to compare the field measured-LAI and the image spectral reflectance was a simple correlation analysis.

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