Grid-layout ultrasonic LoRaWAN-based sensor networks for the measurement of the volume of granular materials

The aim of this paper is to propose a novel methodology for the measurement of volume of masses of granular material: this term encompasses a wide range of materials like grain, sand, coal and so on. The proposed approach is based on the exploitation of grids of ultrasonic ranging sensor nodes, placed above the material mass, exploiting LoRaWAN connectivity for data transmission and measuring the actual level of the material in each single spot. A geometrical approach is applied to the measured data for the computation of the volume. The proposed approach was tested by means of simulations and exploiting a reduced-scale experimental setup: different grid layouts were implemented and tested, with the aim of increasing the measurement accuracy. Since the presented experimental setup can be seen as a worst case scenario, the achieved results can be assumed as an upper bound for the accuracy of the proposed layout.