Hi all.
Quote:
Originally Posted by JayDubo
what datum is the project working off of for lobby to be at elevation +311'-2" and spire to be at +2087'-2"? clearly not the manhattan datum...
update/edit:
a few minutes on google and i've answered my own question...
http://www.pobonline.com/Articles/Co...100000f932a8c0
"Most of the work in New York City, however, is tied to a specific borough datum. In Manhattan for example, the Manhattan vertical datum is 2.75' above mean sea level at Sandy Hook. Transit Authority vertical datum is 100.1' above the Manhattan vertical datum. Similarly, the Port Authority vertical datum is 297.347' above NGVD 29. The Transit Authority and Port Authority, with tunnels well below sea level, use these datums so engineers and surveyors can work in positive numbers."
|
Hi Jay.
That article is worded incorrectly.
The port authority vertical datum, elevation 0 is 297.37 feet
below NGVD 1929. Similarly the transit VD is 100 feet below the Manhattan VD. That is how their deep tunnels stay in positive numbers.