Quantifying Effusion Rates at Active Volcanoes through Integrated Time-Lapse Laser Scanning and Photography

During volcanic eruptions, measurements of the rate at which magma is erupted underpin hazard assessments. For eruptions dominated by the effusion of lava, estimates are often made using satellite data; here, in a case study at Mount Etna (Sicily), we make the first measurements based on terrestrial laser scanning (TLS), and we also include explosive products. During the study period (17–21 July, 2012), regular strombolian explosions were occurring within the Bocca Nuova crater, producing a ~50 m high scoria cone and a small lava flow field. TLS surveys over multi-day intervals determined a mean cone growth rate (effusive and explosive products) of ~0.24 m3s-1. Differences between 0.3-m-resolution DEMs acquired at 10-minute intervals captured the evolution of a breakout lava flow lobe advancing at 0.01–0.03 m3s-1. Partial occlusion within the crater prevented similar measurement of the main flow, but integrating TLS data with time-lapse imagery enabled lava viscosity (7.4 × 105 Pa s) to be derived from surface velocities and, hence, a flux of 0.11 m3s-1 to be calculated. The total dense-rock equivalent magma discharge estimates range from ~0.1 to ~0.2 m3s-1 over the measurement period, and suggest that simultaneous estimates from satellite data are somewhat overestimated. Our results support the use of integrated TLS and time-lapse photography for ground-truthing space-based measurements and highlight the value of interactive image analysis when automated approaches such as particle image velocimetry (PIV) fail

Efficient point cloud corrections for mobile monitoring applications using road/rail-side infrastructure

Light Detection and Ranging (LiDAR) systems are known to capture high density and accuracy data much more efficiently than other surveying methods. Therefore they are used for many applications, e.g. mobile mapping and surveying, 3D modelling, hazard detection, etc. However, while the accuracy of the laser measurements is very high, the accuracy of the resulting 3D point cloud is greatly affected by the geo-referencing accuracy. This is especially problematic for mobile laser scanning systems, where the LiDAR is installed on a moving platform, e.g. a vehicle, and the point cloud is geo-referenced by the data provided by a navigation system. Owing to the complexity of the surrounding environments and external conditions, the accuracy of the navigation system varies and thereby changes the quality of the point cloud. Conventional methods for correcting the point cloud accuracy either rely heavily on manual work or semi-automatic registration methods. While they can provide geo-referencing under different conditions, each has their own problems. This paper presents a semi-automated geo-referencing trajectory correction method by extracting features from the pre-processed point cloud and integrating this information to reprocess the navigation trajectory which is then able to produce better quality point clouds. The method deals with the changing errors within a point cloud dataset, and reducing the trajectory error from metre level to decimetre level, improving the accuracy by at least 56%. The accuracy of the regenerated point cloud then becomes suitable for many accuracy-demanding monitoring and change detection applications

Time-lapse imaging of active lava flows at Mt. Etna, Sicily

Over the last ~6 years, remote time-lapse cameras have been deployed on Mt. Etna, Sicily, with a view to capturing the emplacement of a substantial lava flow field. Initial deployment of wildlife trail-style cameras in 2008 acquired data on lava channel processes during the 2008-9 eruption. In 2009, just in time to capture the dying phases of the eruption, an upgraded network of dSLRs was installed. The network has subsequently captured the steady growth of the New South East crater and the rapid emplacement of short-lived sheet flows that have accompanied the recent paroxysmal fire fountaining events. Most of the imagery has been acquired over distances of multiple kilometres, but the portability of the time-lapse setup has also allowed several opportunistic close range (hundreds of metres or less) deployments, to observe near-vent processes or effusion inside the Bocca Nuova crater. Here, we provide an overview of the equipment, and the approaches used to georeference the monoscopic time-lapse imagery through integrating with 3D data (e.g. existing DEMs, or data simultaneously collected by terrestrial laser scanner or photogrammetric techniques). The acquired observations of flow front emplacement, flow inflation, channel breaching and effusion rate variations that provide insight into the processes involved in long lived flow fields will be presented. Significant opportunities remain, for example, in the near real-time derivation of bulk rheological parameters, and integration with numerical flow models, and the challenges involved in using such imagery will be discussed

When Does a Presidential Candidate Seem Presidential and Trustworthy? Campaign Messages Through the Lens of Language Expectancy Theory

Presidential candidates use different language intensity in different situations. However, the literature is unclear as to when they should use low‐ or high‐intensity language. We applied language expectancy theory and Edwards’ theory of presidential influence to situations varying in circumstances during a presidential campaign. Results indicated significant interactions between language intensity and economic conditions. In support of theories of persuasion applied to presidential campaign contexts, the effects of language intensity and circumstances each depend on the other. During exigent economic times, people consider a presidential candidate to have more presidentiality and trustworthiness when using high‐ instead of low‐intensity language. And during stable economic times, people consider a presidential candidate to have more presidentiality and trustworthiness when using low‐ instead of high‐intensity language