Number of iterations that are required to fix ambiguities for 420 INT2 sessions between Jan. 1st, 2006 and May 30th, 2010. Four different processing strategies have been tested. Red and green bars denote results based on Eqs. (1) and (2), blue and purple bars show results when the functional model is extended by wet-troposphere delay estimation. Each run was made with and without elevation dependent down-weighting. The vertical axis is scaled logarithmically for better readability.