I have some data (points and rasters) that I would like to be able to convert to and from several vertical datums, including MLLW in coastal Florida. I would appreciate it if people could provide some insight into accuracy, pitfalls, requirements, etc. of using available utilities such as VDatum or corpscon. Is one more user-friendly than the other? Are there any others that I should consider? Thanks!
Answer
If you are doing vertical conversions over the ocean you really need to use VDatum.
Vdatum runs a detailed, unstructured mesh tidal model (ADCIRC model, usually), then computes tidal coefficients, generates an 18.6 year time series, then determines surfaces of MLW, MLLW, MHL, MHHW, etc. These surfaces are then evaluated at known tidal gauge locations, and the deviations are used to fit another surface which is then used to adjust the grids so there is no error at the gauge locations.
In the final step they intepolate to a regular grid, which forms the basis so the software conversion. But you can ask for the original surfaces on the original mesh (usually triangular) as well. I did this when I was correcting datums in the Gulf of Maine.
Good luck!
Rich
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