This meeting was held at the Proudman Oceanographic Laboratory, Bidston 

 Observatory in Bidston, U.K. on March 28-31, 1988. The worl<shop ended with 

 the participants agreeing on the following general conclusions: 



• The technology needed to make sea level measurements in hostile 

 regions exists and is affordable; 



• the technology and techniques used must be site specific; 



• bench mark connections are mandatory using the applicable state-of- 

 the-art technology; 



• atmospheric pressure measurements are mandatory using the ap- 

 plicable state-of-the-art technology; 



• real-time data transmission is required to ensure proper operation and 

 early availability of data to the user community; 



• since the availability of global reference systems (Very Long Baseline 

 Interferometry [VLBI] and Global Positioning System [GPS]) has in- 

 creased, the local reference system can be connected to them and 

 subsequently the sea level data measured in relation to the latter will 

 become extremely valuable; 



• bench marks themselves have to meet the technical requirements for 

 the site in view of permafrost disturbances and other local hazards. 



2.6.2 First Session of IOC Group of Experts on the Global Sea-Leve l Observing 

 Syst em (G L QS S) 



This meeting was also held at the Proudman Oceanographic Laboratory, 

 Bidston Observatory in Bidston, U.K. in June 19-23, 1989. The Group discussed 

 the draft report of the Committee on Geodetic Fixing of Tide Gauge Bench Marks 

 (TGBMs) set up by the lAPSO Commission on Mean Sea-Level and Tides. The 

 Group supported the recommendations, technical conclusions and strategy in 

 the report. In particular, it was agreed that the primary strategy of connecting 

 GLOSS (and other) tide gauges with differential GPS measurements to the 

 fundamental VLBI/ Satellite Laser Ranging (SLR) stations of the conventional 

 terrestrial reference frame (of the International Earth Rotation Service [lERS]) was 

 very important for the various oceanographic and geophysical requirements listed 

 in the report. Wherever possible, the vertical movements of the TGBMs should 

 be verified by absolute gravity measurements. 



11 



