University of Twente Student Theses


Exploring the Limits of Mapping Seagrass: A case study for P. oceanica

Noralez, Sylvia Noelly (2010) Exploring the Limits of Mapping Seagrass: A case study for P. oceanica.

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Abstract:Effective identification and mapping of seagrass communities using high spatial and spectral resolution digital imaging spectroscopy are distinguishable by their spectral reflectance characteristics. Hence determining a sunset of wavelength that best discriminates P. oceanica from other seafloor types is essential for development of remote sensing techniques to monitor them. The study measure spectral reflectance of P. oceanica and carbonate sand in the Agia Pelagia Bay, Crete, Greece on a bright sunny day. Laboratory measurements were also conducted. The in situ and laboratory data was spectrally distinct form other seafloor types within the visible spectral range of the spectrum. We compared the results from other to other research and found that the P. oceanica was spectrally distinct within the visible range of the spectrum as it is less attenuated by light. The best discrimination subset of wavelength was identified using the stepwise discriminant function analysis to determine the best discriminant wavebands to identify P. oceanica. These wavelengths are as follows: 328 nm, 408nm, 448nm, 482nm, and 606nm. Major reflectance features were identified in these wavebands. The stepwise discriminant function revealed that spectral separation of the seafloor types is possible with as few as 5 wavebands. The results demonstrate the ability of spectral reflectance characteristics, determined in situ the two seafloor types. Furthermore, to determine whether, P. oceanica remains spectrally distinct a Water Colour Simulator (WASI) model was used to simulate P. oceanica measurement under adverse conditions. These adverse conditions depth of 4 m, 9m, and 20m and CDOM concentration of 0.010 - 0.10m-1. The WASI model was able to simulate the P. oceanica spectra under these adverse conditions. The wavelengths at which they are distinct in adverse conditions were 445, and 485 nm. The remote sensing of P. oceanica is applicable given that the sensor has the bands which are essential for the discrimination of P. oceanica from other seafloor types. The MERIS sensor has proven to be a feasible sensor that could be used to map P. oceanica as the best discriminant bands identified correlates with the spectral bands of the sensor. However, there are factors that need to be considered in doing so to attain the best results for the managing and the monitoring of this important ecosystem.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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