During the
reporting period SC 8 organized the development of a broader working group,
called CGPS@TG, to address the technical issues associated with retrofitting of
tide gauges with continuous GPS stations. This is a joint working group of IAG
(SC 8), IAPSO (CMSLT), the IGS, PSMSL and GLOSS, and has a website at www.soest.hawaii.edu/cgps_tg. We
organized an international meeting in Honolulu, which eventually led to the
production of a position paper 'Technical Issues and Recommendations Related to
the Installation of Continuous GPS stations at Tide Gauges' which was published
by Bevis et al. (2002) as well as being reproduced on the CGPS@TG website. This
website also contains a number of useful case studies. SC 8/CGPS@TG organized a
second and larger international meeting in Toulouse, France in Sept. 2002,
which was funded by the IUGG, with additional support from IOC. Most of the
funding was used to provide travel support, with priority given to scientists
coming from developing countries. This meeting had an associated one-day
workshop for people just entering the field (usually ocenaographers with little
geodesy background, or geodesists with little background in oceanography and
tide gauges). While SC 8 and CGPS@TG have focused mainly in the science driving
the positioning of tide gauges, the technical requirements of field work, and
the accumulation of metadata, we are not funded to perform operational
activities. The most pressing problem in this area was the lack of a suitable
GPS data processing stream. Both SC 8 and CGPS@TG worked with IGS to lobby for,
and later to support the development of an IGS pilot project (TIGA) that will
provide operational support via global geodetic analysis of the data produced
by the CGPS@TG community. Finally, the two international meetings were used to
introduce oceanographers to relevant developments in geodesy and geophyics,
most notably the measurement and modeling of glacial isostatic adjustment
(postglacial rebound), and the difficulties and opportunities presented by
seasonal signals in the position times series of CGPS stations, both at tide
gauges and more generally. The aim of SC8 is an important topic in the
Antarctic research community. In cooperation with the SCAR working group on
Geodesy and Geographic Information (since 2002 "Standing Scientific
Group on Geosciences") the compilation of Antarctic tide gauge data and
their reference to the ITRF by GPS fixing made good
progress. Furthermore, ground truth activities for the new satellite
gravity missions (CHAMP,GRACE) and altimetry missions (ENVISAT,ICESat) have
been supported.
Reference
Bevis, M.,
W. Scherer, and M. Merrifield (2002) Technical Issues and Recommendations
Related to the Installation of Continuous GPS stations at Tide Gauges, Marine
geodesy, 25, 87 - 99.