Preface to the Special Issue of the Journal of Geodetic Sciences on Regional and Global Geoid-based Vertical Datums

The idea of a Special Issue on current research on vertical datums was initially suggested by the co-investigators of the ESA-funded project STSE – GOCE+: Height System Unification with GOCE. Although the participating researchers had been previously presenting their work at various international conferences, it was only when they held one of their progress report meetings in Banff, Canada, that they had the opportunity to all attend and present at the same conference. This conference was the 2012 AnnualMeeting of CanadianGeophysical Union (CGU),where Session G1: Regional and global geoid-based vertical datums was organized and convened byDan Roman of the USNational Geodetic Survey, Michael Sideris of the University of Calgary, and Marc Veronneau of the Geodetic Survey Division of Natural Resources Canada. The Journal of Geodetic Science kindly agreed to devote one of its issues to the subject of SessionG1 and, therefore, the session presenters were invited to submit their papers for peer review andpublication in this Special Issue. In addition, several colleagues working on vertical datums in general, including temporal effects, were also invited to contribute to the Special Issue.