Planning GNSS realistico per applicazioni statiche e cinematiche

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 high 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. In the present work applications performed with the updated version of a planning software, previously developed by one of the author, are illustrated. The software, realized as code integrated in the free and open source GIS GRASS, allows to obtain realistic satellite visibility maps and PDOP index maps taking into account the obstructions to satellite signals due to terrain morphology or buildings, through digital surface models of the interesting area. The procedure, called realistic planning, may be used to find optimal areas in which perform a survey in a given temporal window, or to find the best hour at which plan the survey campaign; it may be applied either to whole areas and to specific trajectory, in adhesion to the terrain or at a given elevation, known the mean velocity of the vehicle. The code was also integrated with the calculus of 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 new permanent stations. By means of such software, a comparative analysis of realistic satellite visibility and PDOP index for a particularly complex area in function of the different GNSS satellite constellations in the course of 24 hours, for static and cinematic applications, and an analysis of the visibility percentage index were performed. The results underline the important contribution of multi-constellations to satellite positioning, mainly in difficult areas, even if actually not yet optimal to allow good surveys in every moment of the day.