"This project attempted to use available information to estimate Mean Sea Surface
Topography (MSST) in sample areas of UK waters and investigate how MSST values
might then be interpolated to produce a mean sea surface. Such a surface would be an
intermediate step in defining a consistent, globally referenced chart datum surface.
The primary dataset contained tidal information at standard and secondary ports in the
UK and Ireland. For those points with sufficient data, the height of mean sea level
(MSL) relative to a geocentric terrestrial reference frame (ETRF89) was calculated. The
OSGM02 gravimetric geoid was then subtracted to produce sea surface topography. The
results were compared with data from satellite altimetry and additional tidal information
from the National Tidal and Sea Level Facility and the Permanent Service for Mean Sea
Level.
The investigation revealed that the primary dataset was very noisy, probably due to
MSL having been measured at different epochs. In addition, during the course of the
research additional evidence became available on datum issues in the Scottish islands.
Considerable further work would be needed both on vertical references for individual
stations and on the OSGM02 corrector surface before the data in these areas could be
used. Interpolation of sea surface topography was considered, in particular how to
include the potential effects of land acting as a barrier. A case study of part of Wales
was used and different methods of calculating distance adjusted to take account of land
obstacles investigated. Further work needs to be done in this area, preferably with an
improved MSST dataset."