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On the field geometrical characterization of illegal micro-dumps by means of RPAS survey with depth camera

Satellite remote sensing is key for large scale monitoring of urban and suburban areas with high revisit time and spatial resolution. However, in some applications involving targets characterized by limited extension and unknown spectral response and spatial distribution, data acquired from space could be insufficient. This is the case of micro-dumps mapping, which represent a highly diffuse environmental hazard in Southern Italy and, in general, in many suburban areas all around the world. Their intrinsic heterogeneity hampers the usage of descriptors based on the spectral response of the targets. The limited extension makes it imaged in few pixels, even using very high-resolution data. In such cases, the exploitation of proximal sensing becomes fundamental. This paper presents a new architecture for real-time characterization of illegal micro-dumps. It is composed, at hardware level, by a customized remotely piloted aerial platform equipped with an innovative payload able to deliver the necessary data for online three-dimensional processing. In particular, a depth camera coupled with a tracking sensor and the drone autopilot (connected with a GPS receiver) is exploited to retrieve a sparse point-cloud, which is geo-localized thanks to positioning information provided by a sensor fusion algorithm. The software component is designed to synchronize, align, segment and extract a volume estimate from the available point cloud with a real time processing. Experimental results show that the developed system is able to deliver accurate volume estimates compared to manual measurements and values obtained via classic offline structure from motion techniques.