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These studies have shown (e.g., Petrachenko et al. 2009, Pany et al. 2011; various IVS Memoranda) that deficiences in tropospheric delay modeling are the major error source for VLBI2010 among the three sources mentioned above. [It is important to note here, that we did not consider source structure effects for the simulations, nor did we simulate systematic effects.]
The simulation of tropospheric delays is based on the turbulence model and the strategy described by Nilsson et al. (2007). In Vienna, the source code by Böhm et al. (2007) is applied. The key parameters for this model are the Cn parameter (structure constant), the effective scale height H, and - to a lesser extent - the wind velocity. A recent list of station-wise parameters as determined by Tobias Nilsson from GPS measurements is provided below. In this table, the scale height is 2000 meters for all sites.
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