Combining TDoA and AoA with a particle filter in an outdoor LoRaWAN network

Internet of Things (IoT) applications that value long battery lifetime over accurate location-based services benefit from localization via Low Power Wide Area Networks (LPWANs) such as LoRaWAN. Recent work on Angle Of Arrival (AoA) estimation with LoRa enables us to explore new optimizations that decrease the estimation error and increase the reliability of Time Difference Of Arrival (TDoA) methods. In this paper, particle filtering is applied to combine TDoA and AoA measurements that were collected in a dense urban environment. The performance of this particle filter is compared to a TDoA estimator and our previous grid-based combination. The results show that a median estimation error of 199 m can be obtained with a particle filter without AoA, which is an error reduction of 10 % compared to the grid-based method. Moreover, the median error is reduced with 57 % if AoA measurements are used. Hence, more accurate and reliable localization is achieved compared to the performance of other baseline methods

LoRaWAN geo-tracking using map matching and compass sensor fusion

In contrast to accurate GPS-based localization, approaches to localize within LoRaWAN networks offer the advantages of being low power and low cost. This targets a very different set of use cases and applications on the market where accuracy is not the main considered metric. The localization is performed by the Time Difference of Arrival (TDoA) method and provides discrete position estimates on a map. An accurate "tracking-on-demand" mode for retrieving lost and stolen assets is important. To enable this mode, we propose deploying an e-compass in the mobile LoRa node, which frequently communicates directional information via the payload of the LoRaWAN uplink messages. Fusing this additional information with raw TDoA estimates in a map matching algorithm enables us to estimate the node location with a much increased accuracy. It is shown that this sensor fusion technique outperforms raw TDoA at the cost of only embedding a low-cost e-compass. For driving, cycling, and walking trajectories, we obtained minimal improvements of 65, 76, and 82% on the median errors which were reduced from 206 to 68 m, 197 to 47 m, and 175 to 31 m, respectively. The energy impact of adding an e-compass is limited: energy consumption increases by only 10% compared to traditional LoRa localization, resulting in a solution that is still 14 times more energy-efficient than a GPS-over-LoRa solution

Minutes de bathymétrie et évolution des fonds marins: les abords du port de Calais

The study of the long-term evolution of the seabed requires detailed knowledge of bathymetry. Hydrographic Service field sheets are more precise than navigation charts and reflect the evolution of the seabed's morphology more accurately

L’évolution du rivage et des petits-fonds en baie de Wissant pendant le XXe siècle (Pas-de-Calais, France)

Le littoral de la Baie de Wissant consiste essentiellement en de larges estrans sableux bordés par des massifs dunaires dont la plupart sont fortement attaqués par la mer. L’analyse de l’évolution du trait de côte entre 1949 et 2000, à l’aide de photographies aériennes verticales, a montré qu’une grande partie de la côte de la baie de Wissant a connu une forte érosion pendant la deuxième partie du xxe siècle, particulièrement dans sa partie centrale où les rythmes de recul ont été de l’ordre de 4 à 5 m/an. Nos résultats montrent également que l’érosion du littoral s’est presque entièrement généralisée à l’ensemble de la baie de Wissant depuis le milieu des années 1970. La seule exception concerne le secteur oriental de la baie, à l’est du village de Wissant, où le rivage a au contraire progressé vers le large. La comparaison de levés bathymétriques datant de 1911, 1977 et 2002 a permis de montrer qu’il existe une nette correspondance entre les zones de forte érosion dans les petits fonds et les secteurs d’important recul de la côte, ce qui suggère que l’évolution de la ligne de rivage est fortement liée aux variations morphologiques de l’avant-côte. Dans l’ensemble, le bilan sédimentaire de la baie est fortement négatif depuis le début du xxe siècle, les pertes de sédiments se chiffrant à plus de 100 000 m3/an. Si l’aggravation de l’érosion littorale pendant le dernier quart de siècle peut en partie être expliquée par des phénomènes naturels comme des variations dans le régime des tempêtes, des facteurs anthropiques ont pu aussi accentuer le déficit sédimentaire de la baie

LoRaWAN geo-tracking using map matching and compass sensor fusion

In contrast to accurate GPS-based localization, approaches to localize within LoRaWAN networks offer the advantages of being low power and low cost. This targets a very different set of use cases and applications on the market where accuracy is not the main considered metric. The localization is performed by the Time Difference of Arrival (TDoA) method and provides discrete position estimates on a map. An accurate "tracking-on-demand" mode for retrieving lost and stolen assets is important. To enable this mode, we propose deploying an e-compass in the mobile LoRa node, which frequently communicates directional information via the payload of the LoRaWAN uplink messages. Fusing this additional information with raw TDoA estimates in a map matching algorithm enables us to estimate the node location with a much increased accuracy. It is shown that this sensor fusion technique outperforms raw TDoA at the cost of only embedding a low-cost e-compass. For driving, cycling, and walking trajectories, we obtained minimal improvements of 65, 76, and 82% on the median errors which were reduced from 206 to 68 m, 197 to 47 m, and 175 to 31 m, respectively. The energy impact of adding an e-compass is limited: energy consumption increases by only 10% compared to traditional LoRa localization, resulting in a solution that is still 14 times more energy-efficient than a GPS-over-LoRa solution

Compass aided TDoA tracking in LoRaWAN networks

LoRWAN nodes can be localized using the TDoA (Time Difference of Arrival) approach. A big advantage is that the geo-location does not consume a lot of energy when compared to GPS approaches. Depending on the use case, the accuracy of the geo-localization (200m) might be a disadvantage. Therefore we propose activating an E-compass in the LoRa node and frequently communicating this directional information over the LoRaWAN network. This extra information can then be fused with TDoA in a map matching algorithm to improve the estimations. We show that our sensor fusion technique is 8 times more accurate than raw TDoA at the cost of only embedding a low-cost e-compass

The characterization of chloroboron (III) subnaphthalocyanine thin films and their application as a donor material for organic solar cells

Chloroboron (III) subnaphthalocyanine (SubNc) films have been characterized by ellipsometry, absorption, photoluminescence measurements, and atomic force microscopy. The films strongly absorb red light, as the extinction coefficient k peaks at 1.4 at a wavelength of 686 nm. Planar bilayer heterojunctions with fullerene (C-60) on top of SubNc are measured under AM 1.5 simulated illumination at various light intensities, leading to an open-circuit voltage (V-oc) of 790 mV and a power conversion efficiency of 2.5%. The external and internal quantum efficiencies peaked at 36% and 70%, respectively. The combination of a strong red absorption and high V-oc make SubNc an interesting material for organic solar cells, in particular for tandem cells.status: publishe