Is there a way to calculate this without using the tools from NOAA website? What is I4 H4 in reference to? Thanks in advance.
Given the Station Name: I4 H4 in Florida and knowing it is a GPS site, what is the NAD 83 (2011) ELLIPSOID HEIGHT?
I4 H 4 (PID AK1515) is a survey disk set in a bridge concrete guardrail.
Its NAD83 (2011) ellipsoid height is 8.663 meters.
See here;
http://www.ngs.noaa.gov/cgi-bin/ds_desig.prl
Type in "I4 H 4" and pick Florida.
FYI - Ellipsoid Ht is not the same as orthometric elevation. Orthometric elevation is what is typically meant when one talks about a points height "above sea level". But even that isn't going to be exactly equivalent to sea level at your location.
You can calculate an ellipsoid height given the ellipsoid parameters, station latitude, ECEF Cartesian coordinates XYZ and the radius of curvature in the prime vertical:
h = rho * cos(Lat) + Z * sin(Lat) - a^2/N
Where
rho^2= X^2 + Y^2
Lat is the geodetic latitude in radians
a is the semi-major axis of the reference ellipsoid
N here is the radius of curvature in the Prime Vertical. Not to be confused with the N designating the geoid-ellipsoid separation.
N = a/sqrt(1-e2*sin(lat)^2)
Where e^2 is the eccentricity of the reference ellipsoid squared.
Note that this is purely geometric.
Not the answer you wanted I guess? The FLDOT submits their control points to the NGS for QC, publication, readjustments when necessary and dissemination.
The "I4 H4" is FLDOT's unique name for the point. It should be the same as what is stamped on the disk. Looks like I4 is used for points on Interstate 4. Contact them for their naming convention.
As Mr Mayer states, an ellipsoid height should not be confused with an orthometric one. Another tidbit on the datasheet is the various values of the ellipsoid height published by the NGS. As you specify a specific NAD version, this is not an issue. Doing work with old data might make it one.
