[PROJ] Strange values with NAVD88

[Javier Jimenez Shaw]

Hi

Doing some tests with NAVD88 (EPSG:5703), I got some unexpected results.
See the next 5 commands

a) echo 40.69 -75.04 0 | PROJ_NETWORK=ON cs2cs EPSG:4979 EPSG:4269+5703 -d 9
     40.689991531 -75.039999022 35.046181369
b) echo 40.69 -75.04 0 | PROJ_NETWORK=ON cs2cs EPSG:4979 EPSG:4152+5703 -d 9
     40.689991800 -75.039998369 35.046181369
c) echo 40.69 -75.04 0 | PROJ_NETWORK=ON cs2cs EPSG:4979 EPSG:6318+5703 -d 9
     40.690000000 -75.040000000 33.784496002
d) echo 40.69 -75.04 0 | PROJ_NETWORK=ON cs2cs EPSG:4979 EPSG:4152 -d 9
     40.690000000 -75.040000000 0.000000000
e) echo 40.69 -75.04 0 | PROJ_NETWORK=ON cs2cs EPSG:4957 EPSG:4152+5703 -d 9
     40.690000000 -75.040000000 33.786615753

Comparing b) and d), why are XY coordinates changed when NAVD88 is
included? It is the same using EPSG:4957 instead of EPSG:4152 in d). I
thought that NAD83(HARN) and WGS84 were considered the same. If it is
considering that the normal to the ellipsoid and the geoid are not the
same, why have d) and e) the same XY coordinates (see that the source in e)
is NAD83(HARN), not WGS84)?

In c), the altitude has more than 1 meter difference. Why? Am I doing or
assuming something wrong? Checking all the american geoids in this area in
cdn.proj.org, there are no more than a few centimeters difference.

I do not know if it is related, but I have only seen ballpark (horizontal)
transformations between NAD83(HARN) and NAD83(2011). Is that correct? I was
expecting some transformation, either direct or a grid.

I am using master, a few days old, hash 2dabb14ec

Thank you.

.___ ._ ..._ .. . ._.  .___ .. __ . _. . __..  ... .... ._ .__
Entre dos pensamientos racionales
hay infinitos pensamientos irracionales.
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