Human populations and natural ecosystems are bound to be exposed to ionizing radiation from the deposition of artificial radionuclides resulting from nuclear accidents, nuclear devices or radiological dispersive devices (“dirty bombs”). On the other hand, Naturally Occurring Radioactive Material industries such as phosphate production or uranium mining, contribute to the on site storage of residuals with enhanced concentrations of natural radionuclides. Therefore, in the context of the European agreements concerning nuclear energy, namely the European Atomic Energy Community Treaty, monitoring is an essential feature of the environmental radiological surveillance. In this work, we obtain 3D maps from outdoor scenarios, and complete such maps with measured radiation levels and with its radionuclide signature. In such scenarios, we face challenges such as unknown and rough terrain, limited number of sampled locations and the need for different sensors and therefore different tasks. We propose a radiological solution for scouting, monitoring and inspecting an area of interest, using a fleet of drones and a controlling ground station. First, we scout an area with a Light Detection and Ranging sensor onboard a drone to accurately 3D-map the area. Then, we monitor that area with a Geiger–Müller Counter at a low-vertical distance from the ground to produce a radiological (heat)map that is overlaid on the 3D map of the scenario. Next, we identify the hotspots of radiation, and inspect them in detail using a drone by landing on them, to reveal its radionuclide signature using a Cadmium–Zinc–Telluride detector. We present the algorithms used to implement such tasks both at the ground station and on the drones. The three mission phases were validated using actual experiments in three different outdoor scenarios. We conclude that drones can not only perform the mission efficiently, but in general they are faster and as reliable as personnel on the ground.

Radiological monitoring is fundamental for compliance with radiological protection policies in the aftermath of radiological events, such as nuclear accidents, terrorism, and out-of-commission uranium mines. An effective strategy for radiation monitoring is to use radiation detectors coupled with Unmanned Aerial Vehicles (UAVs), enabling for quicker surveillance of large areas without involving the need of human presence in the target area. The main aim of this study was to formulate the parameters for a UAV flight strategy in preparation for future field measurements using Geiger–Muller Counters (GMC) and Cadmium Zinc Telluride (CZT) spectrometers. As a proof of concept, the prepared flight strategy will be used to survey out-of-commission uranium mines in northern Portugal. Procedures to assure the calibration of the CZT and verification of the GMCs were conducted, as well as a sensitivity analysis of the sensors considering different acquisition times, distance to source, and detector response time. This article reports specific parameters, such as UAV distance to ground, time of exposition, speed, and the methodology to perform the identification and calculate the activity of possible radioactive sources. An effective flight strategy is also presented, aiming to use radiation detectors coupled with UAVs to undertake extensive monitoring of areas with enhanced levels of environmental radiation, which is of prime importance due to the lasting hazardous effects of enhanced environmental radiation in the nearby ecosystem and population.

Low-power wide-area networks are extending beyond the conventional terrestrial domain. Coastal zones, rivers, wetlands, among others, are nowadays common deployment settings for Internet-of-Things nodes where communication technologies such as LoRa are becoming popular. In this article, we investigate large-scale fading dynamics of LoRa line-of-sight links deployed over an estuary with characteristic intertidal zones, considering both shore-to-shore and shore-to-vessel communications. We propose a novel methodology for path loss prediction which captures i) spatial, ii) temporal and iii) physical features of the RF signal interaction with the environmental dynamics, integrating those features into the two-ray propagation model. To this purpose, we resort to precise hydrodynamic modeling of the estuary, including the specific terrain profile ( bathymetry ) at the reflection point. These aspects are key to accounting for a reflecting surface of varying altitude and permittivity as a function of the tide. Experimental measurements using LoRa devices operating in the 868 MHz band show major trends on the received signal power in agreement with the methodology’s predictions.

Unmanned aerial vehicles (UAVs) recently enabled a myriad of new applications spanning domains from personal entertainment to surveillance and monitoring. In this paper, we focus on using several small UAVs collaboratively to provide extended reach to an online video monitoring system for inspection of industrial installations. We make use of 802.11 radios on low-cost commercial-off-the-shelf UAVs, set up a time-division multiple access overlay protocol to avoid mutual interference, and enable high channel utilization in multihop networks. In particular, we provide a model for the quality of the UAV-to-UAV link, in terms of packet delivery ratio as a function of distance, packet size, and orientation, based on an extensive measurement campaign. We show that this platform is not omnidirectional in the horizontal plane and that UAV-to-UAV communication ceases around 75 m. Concerning the operation in a multihop mode to allow extending the network, the paper derives the optimal number of hops that maximize the end-to-end throughput, as well as the corresponding hop lengths. We validate our mathematical model with extensive experimental measurements transmitting payloads up to 200 m (over 802.11 g at 54 MBps).

Recent advances in Unmanned Aerial Vehicles (UAVs) have enabled countless new applications in the domain of aerial sensing. In scenarios such as intrusion detection, target tracking and facility monitoring it is important to reach a given area of interest (AOI), and create an online data streaming connection to a monitoring ground station (GS) for immediate delivery of content to the operator. In previous work, we showed that a multi-hop line network can increase the range of the mission by finding the optimal number of relay UAVs, and their optimal placement. In this demo, we show that CSMA (typical 802.11's medium access protocol) behaves poorly in this type of networks due to mutual interference, and that TDMA is a better alternative. We will also discuss how changing slot width online can overcome typical and less known TDMA in-efficiencies, and therefore reach maximum end-to-end throughput and low delay.