Satellite-derived bathymetry for nearshore benthic habitats in Timor-Leste from 2010-02-09 to 2013-10-02 (NCEI Accession 0169504)

Bathymetric data derived from multispectral, high-resolution (2 m) satellite imagery from DigitalGlobe's WorldView-2 satellite to provide near complete coverage of nearshore terrain along the northern coastline of Timor-Leste, including the district of Oecusse to the west of mainland Timor-Leste and Atauro Island. Satellite images acquired by the NOAA Coral Reef Ecosystem Program (CREP) for the region are from Jan 26 2010 to August 10, 2014. Methods used by CREP to estimate depths from the WorldView imagery were adapted from instructions developed by Kyle Hogrefe for using IKONOS imagery to derive seafloor elevations in optically clear water (Ehses and Rooney 2015).

Bathymetry values shallower than ~20 m were derived by gauging the relative attenuation of coastal, blue, green and yellow spectral radiance as a function of depth. A multiple linear regression analysis of coastal, blue, green and yellow band spectral values against in-situ depth determined the variables of y-intercept, coastal, blue, green and yellow slope values. The variables for each band were then used in a multivariate slope intercept equation to derive depth over the imagery. Variables and combinations of the bands were adjusted to improve the statistical accuracy and spatial coverage of the final derived bathymetry product. Digital image processing to derive depths was conducted with ENVI, and editing and integration was performed using Esri's ArcGIS.

The method assumes uniform water clarity but deviations from that condition made extraction difficult in water depths greater than 20 m. Results show that biotic material, or sediment in the water column skewed results shallower if the material has a high albedo and deeper if the material has a low albedo.

本数据集由 DigitalGlobe 的 WorldView-2 卫星提供的多光谱、高分辨率（2米）卫星影像生成，旨在对东帝汶北部海岸线及其周边近岸地形实现近乎完整的覆盖，包括东帝汶大陆西侧的奥库西地区和亚图罗岛。NOAA珊瑚礁生态系统计划（CREP）获取的卫星影像数据，时间跨度为2010年1月26日至2014年8月10日。CREP利用Kyle Hogrefe为IKONOS影像生成光学清澈水域的海底高程而开发的指令，对WorldView影像进行深度估算的方法进行了调整（Ehses 和 Rooney 2015）。深度小于约20米的海底测深值是通过测量沿海、蓝色、绿色和黄色光谱辐射亮度相对于深度的相对衰减来获得的。通过将沿海、蓝色、绿色和黄色波段的光谱值与现场深度进行多元线性回归分析，确定了y截距、沿海、蓝色、绿色和黄色斜率值等变量。然后，使用多元斜率截距方程，结合每个波段的变量，推导出影像覆盖区的深度。为提高最终生成的海底测深产品的统计准确性和空间覆盖范围，对波段变量及其组合进行了调整。深度推导的数字图像处理工作使用ENVI完成，编辑和集成则采用Esri的ArcGIS进行。该方法假设水透明度均匀，但在大于20米水深的情况下，偏离该条件会导致提取困难。结果显示，水体中的生物物质或沉积物，若具有高反照率，则结果偏浅；若具有低反照率，则结果偏深。