The Symposium on Vertical Reference Systems (VeReS) was initiated on the
occasion of the XXII General Assembly of the International Union of
Geodesy and Geophysics (IUGG), Birmingham 1999, by Professor Dr.
Wolfgang Torge, Past President of the International Association of
Geodesy (lAG) and representative of lAG to the Pan-American Institute of
Geography and History (PAIGH). The idea was to organise another joint
symposium of lAG and PAIGH like the previous one held during the XX IUGG
General Assembly at Vienna, Austria, in 1991. Good reasons for such a
joint symposium were the great success and the ongoing activities of the
Project on the South American Geocentric Reference System (Sistema de
Referencia Geocentrico para America del Sur, SIRGAS) being sponsored by
lAG and PAIGH since 1993. The SIR GAS Project (Working Group I) had
presented a continental South American reference frame of 58 stations
during the lAG Scientific Assembly at Rio de Janeiro, in 1997. This
reference frame was already adopted by several South American countries
as the basis for their new national horizontal geodetic datums (SIRGAS
Working Group II). To overcome the problems of the heterogeneous
vertical (height) datums between the individual countries, SIRGAS had
installed its Working Group III "Vertical Datum" in 1997. As the
discussion on the unification of vertical reference systems is also
going on in lAG and other bodies of science and practice, it was decided
to dedicate the symposium to this topic.
