[PROJ] Transforming between ITRF realizations

[Trey Stafford]

Hello,

I have a number of elevation datasets that each use a different ITRF 
realization. The coordinates in these datasets are referenced to the 
WGS84 ellipsoid. An example lon, lat, elev(meters above ellipsoid) tuple 
would be:

-117.61748591770593, 59.496749040316935, 329.39612

According to the proj4 documentation on Helmert transformations 
(https://proj4.org/operations/transformations/helmert.html), I should be 
able to use something like this to convert between ITRF2000 and ITRF93:

proj +proj=helmert +convention=position_vector +x=0.0127 +y=0.0065 
+z=-0.0209 +s=0.00195 +dx=-0.0029 +dy=-0.0002 +dz=-0.0006 +ds=0.00001 
+rx=-0.00039 +ry=0.00080 +rz=-0.00114 +drx=-0.00011 +dry=-0.00019 
+drz=0.00007 +t_epoch=1988.0

However, entering my coordinates yield the following result:

0.05    -0.01 329.39612

I've used proj4 previously, but not to do transformations between 
different ITRF realizations. I suspect I am missing something, but I 
have not had revelations yet. Any suggestions or insight would be 
greatly appreciated!

Thanks,

Trey Stafford