Vertical Datum 1

[wcotter]

I am working with some old (100 yr) documents that refer to a local vertical datum that is offset of the mean high water (tide). As the plans are over 100 years old, can I assume that sea level has risen since then? If so, where would I find the historic info needed to "adjust" the record elevations to todays sea level based datum?
Thanks.

 

[RWF7437]

First, I'd suggest you make NO unnecessary assumptions.
If the "documents" you have are drawings or plans see if you can find physical objects shown on them which still exist. Then go out and shoot elevations to find their current elevations based on Mean Sea Level ( not mean high water ).

If you can't do this then you'll have to live with some error. See if you can estimate the magnitude if that unavoidable error. Then see what the consequences of that error are. Can you live with those consequences or can you resolve the differences equitably ?

good luck