[Proj] Is egm08_25.gtx misplaced half a pixel?

[Mikael Rittri]

Hello,

I have tried to use the geoid height file 

   http://download.osgeo.org/proj/vdatum/egm08_25/egm08_25.gtx,

which is discussed here:

   http://trac.osgeo.org/proj/wiki/VerticalDatums

But I am beginning to think that the file is misaligned
(well, at least if ones uses GDAL 1.8 or later to read it).