| VDatum for the coastal waters of Texas and western Louisiana : tidal DAtums and topography of the sea surface - :2640 | National Ocean Service (NOS)
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VDatum for the coastal waters of Texas and western Louisiana : tidal DAtums and topography of the sea surface
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  • Description:
    "VDatum, NOAA's vertical datum transformation software tool, allows users to transform vertical elevation/depth data between various tidal, orthometric, and ellipsoid-based 3D reference systems. An application of VDatum has been developed for the coastal waters of Texas and west Louisiana, which extends the VDatum coverage to all U.S. coastal waters in the Gulf of Mexico region. The tidal datums fields for this VDatum application were derived from tidal simulations using the 2D barotropic version of the finite element model ADCIRC. An unstructured triangular grid consisting of 284,217 nodes and 523,047 cells was created for these simulations. The model was forced with eight tidal constituents (M2, S2, N2, K2, K1, P1, O1 and Q1) and run for 67 days. Water level time series of the last 60 days were saved. Various tidal datum fields, including mean lower low water (MLLW), mean low water (MLW), mean high water (MHW), and mean higher high water (MHHW), were derived from these time series. Water level harmonic analysis was conducted on the model results for the NOAA National Ocean Service's (NOS's) standard 37 tidal constituents. Model results were validated by comparing with observations from 50 water level stations maintained by the NOS's Center for Operational Oceanographic Products and Services (CO-OPS) and 21 additional stations from the Texas Coastal Ocean Observation Network (TCOON). Discrepancies between model results and observational datums were attributed to model errors and interpolated over the whole model domain using TCARI (Tidal Constituent And Residual Interpolation), a spatial interpolation tool based on solution of Laplace's equation. These spatially varying error fields were added to the original model results to derive corrected tidal datum fields on the unstructured grid. These corrected tidal datum fields were then interpolated onto a regularly structured marine grid for use as input to the VDatum software. Non-tidal areas, where the astronomical tide is practically absent, were incorporated into the VDatum tool for the first time. The tide-averaged elevation of the water in these non-tidal areas was defined as the Mean Water Level (MWL), and the differences between the other tidal datums and MWL were set to zero"--Abstract.

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