The special issue of the Bulletin of the Italian Society of Photogrammetry and Topography presents the results of the research conducted within the HELI-DEM project. The study, co-financed with resources OP Italy-Switzerland 2007-2013 – European Regional Development Fund, has assumed a value of a scientific, technological and applicative nature of national and international interest. The main objectives of HELI-DEM were to produce a digital terrain model (DTM) and a geoid model for the Alpine areas between Lombardy, Piedmont and Switzerland.

In addition, the unification of satellite positioning services for professionals and transport control was pioneered. In particular, an optimal DTM construction methodology was identified and applied in the research and an alpine geoid was studied and calculated. The volume, written and published in collaboration with SIFET 2013 – Bulletin of the Italian Society of Photogrammetry and Topography, analytically discusses the objectives, methodologies and results of the HELI-DEM project.