[PROJ] Vertical grid transformation / ellipsoidal height to EGM2008 (EPSG 3855)

[inti luna]

Dear PROJ community,
I am using a GNSS (Emlid REACH RS2 )to collect ground control points for
drone mapping and supporting a project of monitoring vegetation after fire.
I have collected data in LAT,LON (CRS EPSG 4326) and ellipsoidal height (m)
and would like to transform it to another CRS. Target horizontal is EPSG:
25831 and target height is based on EGM2008 (EPSG 3855).

I just discovered PROJ and I am having issues with the vertical
transformation.

Using Linux Ubuntu 11 and installed PROJ using anaconda with:

<conda install -c conda-forge proj>

<conda install -c conda-forge proj-data>

I tested with:

<echo -2.69713764 43.37551925 | cs2cs +init=epsg:4326 +to +init=epsg:25830>

which outputs: -2.69713764 43.37551925 which is fine.

However, I don't understand very well how to perform the vertical grid
shift.

I tried:

1. <echo -2.69713764 43.37551925 102.635| cs2cs +init=epsg:4326 +vgridshift
 +to +init=epsg:25830 +grids=egm08_25.gtx>

2.<echo -2.69713764 43.37551925 102.635 | proj +init=epsg:4326
+proj=vgridshift +grids=egm08_25.gtx>

But the first try ignores the height and the second got me an error message:

"can't initialize operations that produce angular output coordinates
program abnormally terminated"

Thank you for your help,

Inti




-- 
Inti Luna
+ 34 688756449
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