In Differential GPS (DGPS) processing technique the ultimate accuracy of the user location depends on the combined effect of site-dependent errors (i.e. multipath, receiver clock error and etc.), which occur at the points of observation and the reference. Out of which, multipath is recognized as the most dominant and intricate site-dependent error. Previous study by Dammalage et al. (2010) evaluated the possible accuracy improvement of pseudorange-based DGPS positioning by C/A code multipath mitigation at the GPS reference stations applying wavelets transform. In this paper, three factors, which degrade the obtainable accuracy of the proposed multipath mitigation method, are identified and results are presented.