Planning GNSS realistico.

The more and more spread presence of GNSS Permanent Station Networks makes the satellite survey techniques more simpler, quicker and cheaper, allowing the technician to obtain easily sub-decimetric precisions. However, the result and, above all, the speed of GNSS survey campaign get an advantage out of accurate planning, especially where the site to survey has characteristics that make the satellite observations difficult. To facilitate the search of sites suitable for the installation of GNSS permanent stations, a planning software, previously developed by one of the author, has been updated; it allows to obtain realistic satellite visibility maps, taking into account of the terrain morphology or buildings through digital surface models of the interesting area. By means of such software, a comparative analysis of satellite visibility in function of the different GNSS satellite constellation in the course of 24 hours in a particularly complex area was performed. The evaluation of satellite numbers realistically visible is integrated with an index of visibility percentage with respect to the number of satellite observable without obstructions, so to make easy the choice of the site for the future GNSS permanent stations of Piedmont Region.