VDATUM: the Vertical Datum Transformation Tool. Kurt Hess Office of Coast Survey. A vertical datum is a reference surface for elevations NOAA Chart Datum for Depths: Mean Lower Low Water (MLLW) NOAA Shoreline: Mean High Water (MHW) . RTK/PPK-GPS Hydrographic Surveys.
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Office of Coast Survey
Depths are measured “on the fly” relative to ellipsoidal datum (e.g., WGS84). Depths need to be converted to chart datum (MLLW).
NAVD 88, NGVD 29
NAD 83Need to Integrate Land and Water Datasets with Different Elevation Reference Systems
(Tidal Datums) (Intertidal) (Orthometric Datums)
How to convert between these various datums? Vdatum Conversion SoftwareTidal DatumsMHHWMHWMSLMLWMLLW
DELAWARE BAY PPK-GPS SURVEY, June 2001 Conversion Software
VDatum gives a more realistic
series of depths values
VDatum vs Zoning
‘Jump’ due to
Inundated areas due to a 30 cm sea level rise
LIDAR data transformed from ellipsiodal to the MHW datum using VDatum.
NOAA T-Sheet MHW shoreline (1977)
0 m contour is MHW shoreline (1996)
VDATUM TODAY using VDatum.
Areas where VDatum tool is complete and available to the public
Issues using VDatum.