[PROJ] Converting NAD83/NADV88 heights to HAE

[Patrick Young]

Ah yes, I mean that projsync pulls us_noaa_g2018u0.tif but the readme
refers to us_nga_g2018u0.tif

On Wed, Jul 1, 2020, 6:36 PM John Helly <hellyj at ucsd.edu> wrote:

> Don't know about your overall problem but NGA is probably the National
> Geospatial Agency and NOAA is National Oceanic and Atmospheric Agency:
> i.e., not just a typo.
>
> J.
>
> On 7/1/20 16:49, Patrick Young wrote:
>
> 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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>
> --
> John Helly, University of California, San Diego / San Diego Supercomputer Center / Scripps Institution of Oceanography / 760 840 8660 mobile / http://www.sdsc.edu/~hellyj
> ORCID ID: orcid.org/0000-0002-3779-0603
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