Integrating geographical data with surveys conducted with UAVs for planning areas of high environmental value
The setting up of a general framework for the environmental and landscape planning of a protected area, requires a basic detailed survey of this area and its vegetation, accompanied by a monitoring of the latter, so that a specific maintenance plan can be implemented accordingly. With reference to an area of high environmental, landscape and archaeological value, such as the 'Pulo di Molfetta' (Municipality of Molfetta – Southern Italy), some georeferenced floristic surveys have been carried out, with relative mapping and monitoring of the vegetation growth. In this way, it has been possible to draw up some detailed management measures for the vegetation, as well as to plan suitable interventions of ecological engineering, aimed at determining the most appropriate conditions for the recovery, use and sustainable management of this study area, even for tourism purposes. These activities have been conducted through the construction of a basic model, which has been implemented in a Geographical Information System (GIS), structured on the basis of some Free and Open-Source geographic data, integrated with a geo-localized 3D survey of the geomorphology, architectural structures and the flora-vegetation habitat. The survey, georeferencing and 3D model formation operations have been conducted by means of:
1) a photogrammetric survey at ultra-low height – variable, according to the orography - carried out with Unmanned Aerial Vehicles (UAVs), to obtain a 3D digital modelling, having a readable resolution of at least 2 cm/pixel;
2) coverage with a block of frames with nadiral and sub-horizontal orientation, for a readability optimized to the analysis of both the geomorphology and the existing medium and tall vegetation;
3) creation of a framing and support network, materialized with high-contrast photographic targets, measured with RTK methodologies of GNSS satellite positioning and accuracy ≤ 3 cm, georeferenced in the RDN2008 Reference Coordinate System - as per Italian regulations;
4) restitution of a 3D digital model, obtained with SfM (Structure from Motion) technologies, formed by a resolution of 1-2 cm, point clouds, triangular mesh and photographic texture;
5) formation of a very-high resolution ortho-photomosaic, with GSD (Ground Sampling Distance) ≤ 15 mm, and of an adequate number of radial sections, with two views, each one orthogonal to the section plane;
6) georeferenced identification of the individual floristic-vegetational elements and help for the construction of a database containing the agreed attributes defined and aimed at planning the vegetation layers present.
The metric analyses have been conducted with commercial instruments, such as UAVs systems, GNSS and photogrammetric processing software, in order to test a very widespread, low-cost operational chain in the dimensional and qualitative survey of medium-small extensions, affected by great biodiversity and an important altimetric variation such as a karst sinkhole.
In conclusion, the results thus obtained have allowed for the inclusion of the geo-localized 3D model in a GIS base for the knowledge of the flora-vegetation habitat, thanks to which it will be possible to provide support for the decision-making of planning choices for the territory, landscape and environment of the study area, as well as its close surroundings, so as to safeguard its biodiversity and ecosystem relations.