Vertical Datum Conversions for Regional Coastal Management
CORPS OF ENGINEERS MOBILE AL MOBILE DISTRICT
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Transforming surveyed elevations and water depths to desired vertical datums is an essential step in building a regional coastal management plan. Regional coastal management plans are based on sediment volume changes and numerical simulations of regional coastal change. Computation of sediment volume changes are possible only if the survey data sets compared share the same vertical datum. Some numerical simulations of regional coastal change require a baseline data set that is referenced to a particular stage of the tide. Until recently hydrographic and topographic surveys covered areas that were sufficiently small to require only a simple vertical shift to convert the survey data to the desired vertical datum based on local established benchmarks. Data sets that cover large areas are now available through rapid survey techniques like airborne lidar and through digital publishing of data like that found on nautical charts. These data sets are not easily converted to a common datum. The magnitude of this problem for regional applications is being recognized only now. The vertical location of tidal geodetic and ellipsoidal datums can vary widely over the large areas that these data sets cover. The datums are derived at discrete points distributed sparsely through an area. This paper outlines methodologies for developing and applying regional datum conversions. The methods presented are designed both to realistically represent vertical datums as surfaces instead of discrete points within a region and to minimize error in volume computations and numerical simulations for regional coastal management.
- Information Science
- Hydrology, Limnology and Potamology