EGM96 Transformation - Ambiguous error on the help web page

[GeordieHobart]

I am doing some conversions from ellipsoidal to geoid heights and was referring to the help page http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009t000001vm000000 (Converting from orthometric to ellipsoidal heights).

The problem is that the equation

h = H + N

Where
h = ellipsoidal height
H = orthometric (geoid) height
N = geoidal separation


is restated further down the page as 

H = N - h

which is not equivalent.

Which equation is correct? I suspect that the first equation is correct but would prefer to have some independent confirmation of this as opposed to assuming. Thanks in advance.

[MelitaKennedy]

The first equation,

h = H + N

is correct which means the second is not. It should be:

H = h - N

My references include Wolfgang Torge's Geodesy, 2nd Edition and National Geodetic Survey. I've sent an email to a colleague on the raster team.

Melita