015 m) and were referenced to NAVD88 using a Federal Base Network Control Station maintained by the National Geodetic Survey at the U.
As represented by the column labeled Delta, conversion values from Marindin's 19th century mean sea level datum to NAVD88 range from -0.
The recovery of several historical benchmarks is critical to minimize general assumptions that would otherwise be required to translate this local tidal datum and associated historical elevation data to NAVD88.
Elevations for each benchmark and the relationship of Marindin's mean sea level datum to NAVD88 are compiled in Table 3.
Recovery of several benchmarks and the ability to estimate a reliable conversion from a historical plane of reference to NAVD88 reduces the potential uncertainty associated with comparisons of a century old and contemporary spatial data.
Further, MHD elevations were referenced to NGVD29 and while these elevations could have been converted to NAVD88, issues with reported NGVD29 values on the outer Cape have been identified routinely by local surveyors and for this reason reported values were not used in this study.