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Lookup NU author(s): Professor Richard Birmingham,
Dr Meredith Williams
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The determination of shallow water depth is essential for local navigation within the territorial waters of Saudi Arabia. The objective of this research was to develop a method for production of accurate bathymetry maps of shallow water areas in the red sea using high spatial resolution multispectral IKONOS satellite imagery and field measurement. Two study sites were utilized for this research, representing the extremes of water conditions encountered in the region. The first site, representative of turbid water conditions, was the Rabigh port maneuvering area. The second site at Shab Tanta was representative of clear water conditions within coral reef areas. Simple linear regression was applied to relate field measured water depths to pixel brightness values in the blue band of IKONOS multispectral imagery that had been corrected to at-satellite reflectance using published calibration coefficients. The regression relationship at the clear water site was highly accurate (r2 = 97%) for water depths in the range 2 to 18 metres. Some deterioration in the regression fit for turbid regions was noted, due to variability in image reflectance, but an r-squared fit of 81.9% was achieved, which meant that the linear equation was transferable between the sites. Finally a comparison between actual depth measured by hydrographic echo sounder during the field measurement and the estimated depth derived from satellite images was made to establish the margins of error in the estimates. A mean of error of 2.65% (SD = 3.3m, Median = 1.7) overall, with an accuracy of 97.3% was found. This result demonstrates that, for this region, depth estimations of sufficient accuracy for bathymetric mapping can be derived from IKONOS imagery without the need to collect in-situ atmospheric measurements or field spectroscopy for correction to at-surface reflectance values.
Author(s): Birmingham R, Williams M, Al-Zahrani A
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Unknown
Conference Name: The Inland Water Transport 3rd International Conference and Exhibition (MELAHA)
Year of Conference: 2006