Integrated techniques for low-cost surveying of urban areas

This paper deals with the purpose of a methodology integrating different surveying techniques to efficiently produce a large-scale digital mapping of urban areas. At first, a comparison among methods for reuse/updating of existing maps, aerial modern techniques and terrestrial ones is carried out, highlighting the pros/cons characterizing each one and in the attempt to find the “best technique” as well a suitable integration/synergism among them. The integration herewith adopted considers the availability of a 3D-vector numerical mapping and the photogrammetric exploiting of images acquired either (dynamically) by a low-cost MMS or (statically) by a non-metric high-resolution CCD. MMS allows the survey of 3D-control points for the successive processing of the CCD images. Afterwards for such techniques, the global work strategy and the different analytical model applied are explained. The main features of the algorithm for MMS data processing are: a direct/indirect orientation model, the stochastic prediction of point coordinates, and a pseudo-dynamic solution approach. Moreover, the analytical model of photogrammetric use of CCD images takes into account the inauspicious errors due to MMS survey by means of suitable techniques for stochastic prediction of unknowns. At the paper end, the promising results obtained from an application on real data of this integrated method are shown and evaluated.