Photogrammetric survey of terrains

SAL Engineering designs and manufactures integrated systems for photogrammetric surveys of land in the field of hydrogeological instability, protection of the territory, hydrogeological prevention, planning of roads, infrastructure design. The photogrammetric survey is planned in the laboratory and is conducted on hydrographic basins, agricultural fields, forests and archaeological sites with multi-rotor drones, fixed wing drones and real aircraft depending on the size of the relief.
The surveys are intended to produce 3D models with high precision and accuracy, with strict data acquisition procedures from a scientific point of view and methodologies that presuppose the validation and repeatability of the survey.
The survey system consists of a remote control aerial, gimbal for stabilized image acquisition, and photogrammetric sensor. The integration of inertial platform and GNSS positioning system allows to carry out scheduled and stabilized flights via waypoints; an additional GPS allows the georeferencing of each photo, in order to obtain a more rapid and accurate 3D reconstruction.
The acquisition of geo-referenced images is complementary to a topographic survey on the ground; various GCP (Ground Control Points), visible in the photos, are measured by a GNSS system or a high precision total station, in order to optimize the bundle adjustment process, georeference the 3D model and insert it into a geodetic reference system.
In the case where a portion of the relief area is not suitable for the photogrammetric survey, a topographic survey is performed and then the data are integrated in the point cloud in order to create a complete model of the entire area.
The images and GNSS data are processed with the most developed photogrammetric software that use the structure from motion and bundle adjustment algorithms for the creation of a high density cloud point (in which the RGB data is also present), from which it is possible extract different products.
These products are DSM (Digital Surface Model), DTM (Digital Terrain Model), orthophotos, level curves, topographic sections, vector data for updating local cartography, volumetric data for geological interpretation. The research and development section within SAL Engineering, which boasts numerous publications in trade magazines, guarantees high standards of precision, accuracy and repeatability of the three-dimensional data. These products can be used in GIS, CAD, and BIM environments. A flexible, non-invasive and economic procedure allows a wide range of applications such as the monitoring of areas subject to hydrogeological instability, coastal areas, or the updating of local cartography for planning and territorial planning purposes.