HR: 1400h
AN: G33B-01    [Abstracts]
TI: A New Vertical Reference System for South America
AU: * Sanchez, L
EM: sanchez@dgfi.badw.de
AF: Deutsches Geodaetisches Forschungsinstitut, Alfons-Goppel-Str. 11, Munich, BAV D- 80539, Germany
AB: A main objective of a modern vertical reference system is to satisfy h = H + N world wide. It requires the definition and realisation of a unique physical reference surface, and the linkage of the local reference levels to the global one. Based on the gravity field missions and satellite altimetry data an accurate global reference level (W0) can be determined. Its realisation (the geoid) on marine areas becomes feasible by solving the classical boundary value problem (BVP). On continental areas, it is more complicated: besides the hypothesis to determine the geoid, the observables included in the BVP are affected by the inconsistencies of the height datums. In this way, four steps must be followed: 1) Solution of the BVP according to Molodenskii Theory, 2) Connection of the local levels with the global reference surface, 3) Recalculation of the height-related observables to iterate the BVP and, 4) Repetition of the procedure until getting a mm-level accuracy in normal heights and height anomalies. The central problem is to find the adequate strategy to unify the local height datums. Our proposal is: a) joint analysis of tide gauge and satellite altimetry data to determine the time variation of sea level at the reference tide gauges, b) continuously GNSS positioning at the same reference points to separate crustal movements from sea level rise, c) evaluation of physical and geometrical heights on a high-precise reference frame, and d) connection of the existing height datums. The unification of the South American classical vertical datums is presented as an example of the proposed methodology.
DE: 1229 Reference systems
SC: Geodesy [G]
MN: 2007 Joint Assembly