WA Bathymetry CoNED MLLW

For the purposes of research and monitoring in marine environments, elevation data is typically most useful when it is expressed relative to tidal rather than orthometric vertical datums. For example, the potential habitat depth of submerged aquatic vegetation is often expressed as a range relative to mean lower low water (MLLW), representing the specific light requirements of each species. This MLLW bathymetric model (elevation values in meters) of the southern Salish Sea is based on the USGS CoNED topobathymetric digital elevation models of Puget Sound (OCM Partners, 2022a) and the Strait of Juan de Fuca (OCM Partners, 2022b), converted from NAVD88 to MLLW using NOAA’s VDatum 4.6.1 transformation grids (Office of Coast Survey, 2023), and projected onto NAD 1983 HARN StatePlane Washington South FIPS 4602. For more information, contact Tyler Cowdrey, WA DNR, Nearshore Habitat Program at: [e-mail] or [e-mail]. Suggested citation: Cowdrey, T. (2024). Washington State USGS CoNED MLLW Bathymetric DEM [Data Set]. Washington State Department of Natural Resources, Nearshore Habitat Program. [https://gis.dnr.wa.gov/image/rest/services/Aquatics/WA_bathymetry_CoNED_MLLW/ImageServer]. The values of MLLW in this model were generated using source and intermediate data products with significant interpolation and are intended for informational and research purposes only. This product has not been reviewed by a licensed surveyor and should not be used in place of professional surveys for the assessment of tideland parcel boundaries. This product should not be used for navigation. WA DNR makes no warranties about the accuracy of this product. Rough processing workflow: CoNED tiles were bulk downloaded in GeoTIFF format from NOAA Digital Coast (https://coast.noaa.gov/htdata/raster2/elevation/). VDatum 4.6.1 was used to generate NAVD88 to MLLW transformation grids at a resolution of ~0.0002 degrees in ITRF14, which were were then combined and projected onto NAD 1983 (2011) UTM 10N and resampled at 1 meter resolution (snapped to CoNED) using bilinear interpolation. The combined grid was then used to batch transform CoNED tiles from NAVD88 to MLLW using ArcPy maintaining extent, PCS, cell size and snap raster. The new CoNED MLLW tiles were mosaicked and projected onto NAD 1983 HARN StatePlane Washington South FIPS 4602 (SPWAS) as a continuous raster to prevent tile discontinuities. Finally, the continuous CoNED MLLW SPWAS raster was re-tiled, tiles were named by row and column, and pixel values above 10 meters of elevation were removed to improve the reliability of the final product for marine applications. References: OCM Partners. 2022a. 1887 - 2017 USGS CoNED Topobathy DEM (Compiled 2020): Puget Sound, WA. NOAA National Centers for Environmental Information. https://www.fisheries.noaa.gov/inport/item/59971. OCM Partners. 2022b. 1891 - 2016 USGS CoNED Topobathy DEM (Compiled 2021): Strait of Juan de Fuca, WA. NOAA National Centers for Environmental Information. https://www.fisheries.noaa.gov/inport/item/65169. Office of Coast Survey, N.O.A.A., U.S. Department of Commerce. 2023. Vertical Datum Transformation (VDatum 4.6.1). https://vdatum.noaa.gov/download.php.在海洋环境的研究与监测工作中，以潮汐垂直基准面而非正高垂直基准面表达的高程数据通常具备更高的应用价值。例如，沉水水生植被的潜在栖息水深通常以相对于平均低潮面（mean lower low water, MLLW）的区间来表征，以匹配各物种对光照的特定需求。 本南萨利希海平均低潮面（mean lower low water, MLLW）水深高程模型（单位为米）的数据源为普吉特湾（OCM Partners, 2022a）与胡安·德富卡海峡（OCM Partners, 2022b）的美国地质调查局（United States Geological Survey, USGS）海岸国家高程数据库（Coastal National Elevation Database, CoNED）地形水深数字高程模型（Digital Elevation Model, DEM），通过美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）的VDatum 4.6.1转换格网（海岸测量办公室, 2023）将其从北美垂直基准面1988（North American Vertical Datum 1988, NAVD88）转换至MLLW基准，并投影至NAD 1983 HARN华盛顿州南州平面坐标系（FIPS 4602）。 如需获取更多信息，请联系华盛顿州自然资源部（Washington Department of Natural Resources, WA DNR）近岸栖息地项目的泰勒·考德雷（Tyler Cowdrey），邮箱：[e-mail] 或 [e-mail]。 推荐引用格式：考德雷, T. (2024). 华盛顿州USGS CoNED MLLW Bathymetric DEM [数据集]. 华盛顿州自然资源部近岸栖息地项目. [https://gis.dnr.wa.gov/image/rest/services/Aquatics/WA_bathymetry_CoNED_MLLW/ImageServer] 本模型中MLLW基准下的高程值通过源数据与中间数据产品经大量插值生成，仅用于信息参考与研究用途。本产品未经过注册测量师审核，不得替代专业测量工作用于潮地地块边界评估，亦不得用于导航用途。华盛顿州自然资源部不对本产品的准确性作出任何担保。 简要处理流程如下：从NOAA数字海岸平台（https://coast.noaa.gov/htdata/raster2/elevation/）批量下载GeoTIFF格式的CoNED分幅数据。使用VDatum 4.6.1生成国际地面参考框架14（International Terrestrial Reference Frame 14, ITRF14）下分辨率约0.0002度的NAVD88至MLLW转换格网，随后将其合并并投影至NAD 1983 (2011) 通用横轴墨卡托10北带（Universal Transverse Mercator 10N, UTM 10N）坐标系，以双线性插值法重采样至1米分辨率（对齐至CoNED数据）。利用合并后的格网通过ArcPy批量将CoNED分幅数据从NAVD88基准转换至MLLW基准，保留范围、投影坐标系（Projected Coordinate System, PCS）、像元大小与对齐栅格。将转换后的CoNED MLLW分幅数据拼接为连续栅格，并投影至NAD 1983 HARN华盛顿州南州平面坐标系（FIPS 4602，简称SPWAS），以消除分幅间的不连续性。最后将该连续CoNED MLLW SPWAS栅格重新分幅，按行列命名分幅文件，并移除高程值高于10米的像元，以提升本产品在海洋应用中的可靠性。 参考文献： OCM合作伙伴团队. 2022a. 1887-2017年美国地质调查局CoNED地形水深数字高程模型（2020年汇编）：华盛顿州普吉特湾. 美国国家海洋和大气管理局国家环境信息中心. https://www.fisheries.noaa.gov/inport/item/59971. OCM合作伙伴团队. 2022b. 1891-2016年美国地质调查局CoNED地形水深数字高程模型（2021年汇编）：华盛顿州胡安·德富卡海峡. 美国国家海洋和大气管理局国家环境信息中心. https://www.fisheries.noaa.gov/inport/item/65169. 美国商务部国家海洋和大气管理局海岸测量办公室. 2023. 垂直基准面转换工具（VDatum 4.6.1）. https://vdatum.noaa.gov/download.php.