[PROJ] Converting NAD83/NADV88 heights to HAE

[Patrick Young]

Hello,

I am trying to figure out how to convert some elevations I have into
heights above ellipsoid via the cs2cs tool.  I am using proj 7.0.1, and
I've run projsync --all to snag all the grids.

Here is an example of what isn't working for me:

echo 565890.947 4192011.754 55 | cs2cs +proj=utm +zone=10 +datum=NAD83
+units=m +no_defs +geoidgrids=us_noaa_g2018u0.tif +to +proj=utm +zone=10
+datum=NAD83 +units=m +vunits=m +no_defs
565890.95       4192011.75 55.00

I am confused as to why the elevation value isn't changing for me.  My
(extremely limited) understanding is that I am asking for 55m to be
converted from a height referenced against the NADV88 geoid to one
referenced against the NAD83 ellipsoid.  Am I using the wrong geoid grid?
>From the grid readme, it mentions "us_nga_g2018u0.tif : Conterminous US,
referenced to NAD83(2011). Vertical datum: NAVD88"  (presumably the nga <->
noaa is a typo in the readme) so I think I'm using the right one.

Thanks for any help,
Patrick
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