Sandy Hook Datum

The Louisiville District has this Table. The Huntington District should have something similar, but a quick search of their web page didn't turn anything up.

Yeah, I saw that. It gives me an idea, but I need something a little better.

The NGVD 29 should not be confused with the "Sandy Hook Datum." Regrettably the U.S. Coast & Geodetic Survey never specifically used the name to identify a datum. It has commonly been used to describe what are more technically referenced as the First(1899), Second(1903), Third(1907) and Fourth(1912) General Adjustments of the level nets of the United States. You can find links to all four publications on the NGS Vertical Publications web page -- http://www.ngs.noaa.gov/PUBS_LIB/pub_vert.shtml .

The USC&GS tide station at Sandy Hook was one of the primary sites held fixed in the early vertical leveling adjustments by using local Mean Sea Level as determined during 1876-1881. It was the primary station used in the First General Adjustment (1899) and the name just sort of stuck.

That being said USC&GS never ran a level line on any of these reference systems in the vicinty of Ashland, Ky. Without addition information on where your reference to the datum came from I can only provide a general relationship based on leveling performed during 1897-1898 by the U.S. Geological Survey and described in their 1909 publication Bulletin 411 "Spirit Leveling in Ohio, 1898 to 1908, Inclusive." On page 67 there is a reference to one of their bench marks set in Ironton, OH at the memorial Hall and Public Library for which they provide a height of 546.177 ft. This mark was leveled to by USC&GS in 1958 and is designated 544 I (pid HY1376) in the National Spatial Reference System with an NGVD 29 height of 546.05 ft and an NAVD 88 height of 545.44 ft. Differences there are:

Sandy Hook to NGVD 29 = -0.13 ft
Sandy Hook to NAVD 88 = -0.74 ft

There are several bench marks published by USGS in their 1914 publication Bulletin 554 "Results of Spirit Leveling in Kentucky 1898 to 1913 Inclusive" which are specifically identified as related to the 1912 Fourth General Adjustment. Unfortunately none of these marks appear to have been included in the NGVD 29 or NAVD 88 adjustments. Without more information I would suspect that one of more of these could be the marks used to reference your data. The only way to determine the most appropriate offset would be to try and recover and redetermine one or more of these stations. Unfortunately this publication is not digital. If you would like copies of the descriptions and corresponding referenced send me an e-mail - dave.doyle@noaa.gov

Sandy Hook Datum