Permanent GNSS networks and official geoid undulations model as a substitute for orthometric control
Steinberg, Gershon and Gilad Even-Tzur
For many years Vertical Geodetic Control was the nickname of a framework of control points (benchmarks) having Orthometric Heights achieved by precise leveling. Precise leveling is indeed a highly accurate measuring method, but it is notoriously time-consuming, very expensive in terms of manpower and extremely cumbersome in having to cover literally stepby- step the space between every pair of end-points. Motorized leveling has solved part of the slowwrate problem, but the price remains high, and still a lengthy meandering is needed in order to cross mountains, wide rivers or lakes. There are areas where precise leveling is practically impossible. The objective of any primary leveling system is to provide a framework on which topographers and engineers can base and adjust their heights with expectation that, except quite locally, its errors will be less than theirs. Another important objective of the primary leveling system was to monitor vertical tectonic changes over a wide area. This objective is achieved already much better by GNSS measurements. We suggest that the first objective of a primary leveling system can be also achieved much easier with reasonable accuracy on nationwide basis, by a combination of Ellipsoidal Vertical Control (through GNSS measurements) and Official Geoid Undulations Model. Elaboration of this idea is the heart of the paper.
Event: XXIII International FIG Congress : Shaping the change
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