Alessandro Fornaciai

Short note: Release of a 10-m-resolution DEM for the Italian territory: Comparison with global-coverage DEMs and anaglyph-mode exploration via the web

The 10-m-resolution TINITALY/01 DEM (Tarquini et al., 2007) is compared with the two, coarser-resolution, global-coverage, spaceborne-based SRTM and ASTER DEMs and with a high-resolution, LIDAR-derived DEM. Afterwards, we presented a webGIS which allows to explore a 10-m-resolution anaglyph layer showing the landforms of the whole Italian territory in 3D. The webGIS (http://tinitaly.pi.ingv.it/) is open to the public, and can be used to carry out a preliminary analysis of landforms. The TINITALY/01 DEM is available for scientific purposes on the basis of a research agreement (see the above website or write to tinitaly@pi.ingv.it).

Evolution of an active lava flow field using a multitemporal LIDAR acquisition

This work was partially funded by the Italian 930 Dipartimento della Protezione Civile in the frame of the 2007–2009 Agree- 931 ment with Istituto Nazionale di Geofisica e Vulcanologia–INGV. A.F. 932 benefited from the MIUR‐FIRB project “Piattaforma di ricerca multi‐disci- 933 plinare su terremoti e vulcani (AIRPLANE)” n. RBPR05B2ZJ. S.T. 934 benefited from the project FIRB “Sviluppo di nuove tecnologie per la prote- 935 zione e difesa del territorio dai rischi naturali (FUMO)” funded by the Italian 936 Ministero dell’Istruzione, dell’Universita e della Ricerca.

Multiview 3D reconstruction in geosciences

Multiview three-dimensional (3D) reconstruction is a technology that allows the creation of 3D models of a given scenario from a series of overlapping pictures taken using consumer-grade digital cameras. This type of 3D reconstruction is facilitated by freely available software, which does not require expert-level skills. This technology provides a 3D working environment, which integrates sample/field data visualization and measurement tools. In this study, we test the potential of this method for 3D reconstruction of decimeter-scale objects of geological interest. We generated 3D models of three different outcrops exposed in a marble quarry and two solids: a volcanic bomb and a stalagmite. Comparison of the models obtained in this study using the presented method with those obtained using a precise laser scanner shows that multiview 3D reconstruction yields models that present a root mean square error/average linear dimensions between 0.11 and 0.68%. Thus this technology turns out to be an extremely promising tool, which can be fruitfully applied in geosciences.

Lava flow hazard and risk at Mt. Cameroon volcano

Mt. Cameroon is one of the most active effusive volcanoes in Africa. About 500,000 people living or working around its fertile flanks are subject to significant threat from lava flow inundation. Lava flow hazard and risk were assessed by simulating probable lava flow paths using the DOWNFLOW code. The vent opening probability density function and lava flow length distribution were determined on the basis of available data from past eruptions at Mt. Cameroon volcano. Code calibration was performed through comparison with real lava flow paths. The topographic basis for simulations was the 90-m resolution SRTM DEM. Simulated lava flows from about 80,000 possible vents were used to produce a detailed lava flow hazard map. The lava flow risk in the area was mapped by combining the hazard map with digitized infrastructures (i.e., human settlements and roads). Results show that the risk of lava flow inundation is greatest in the most inhabited coastal areas comprising the town of Limbe, which constitutes the center of Cameroon’s oil industry and an important commercial port. Buea, the second most important town in the area, has a much lower risk although it is significantly closer to the summit of the volcano. Non-negligible risk characterizes many villages and most roads in the area surrounding the volcano. In addition to the conventional risk mapping described above, we also present (1) two reversed risk maps (one for buildings and one for roads), where each point on the volcano is classified according to the total damage expected as a consequence of vent opening at that point; (2) maps of the lava catchments for the two main towns of Limbe and Buea, illustrating the expected damage upon venting at any point in the catchment basin. The hazard and risk maps provided here represent valuable tools for both medium/long-term land-use planning and real-time volcanic risk management and decision making.

A new approach to risk assessment of lava flow at Mount Etna

Destruction of human property by lava flow invasion is a significant volcanic hazard at Mount Etna (Italy), where reliable risk maps are important for risk mitigation. We present new high-resolution quantitative risk maps of Mount Etna that are based on lava flow simulations starting from more than 70,000 different potential vents, a probability distribution of vent location, an empirical relationship for the maximum length of lava flows, and a database of buildings. In addition to standard risk maps, which classify areas according to the expected damage at each point, we classify each point of the volcano with respect to the damage that would occur if a vent opened at that point. The resulting maps should help local authorities in making the necessary decisions to deal with ongoing eruptions and to plan long-term land use.

A LiDAR survey of Stromboli volcano (Italy): Digital elevation model-based geomorphology and intensity analysis

LiDAR (Light Detection and Ranging) is a novel and very useful active remote sensing system which can be used to directly identify geomorphological features as well as the properties of materials on the ground surface. In this work, LiDAR data were applied to the study of the Stromboli volcano in Italy. LiDAR data points, collected during a survey in October 2005, were used to generate a Digital Elevation Model (DEM) and a calibrated intensity map of the ground surface. The DEM, derived maps and topographic cross-sections were used to complete a geomorphological analysis of Stromboli, which led to the identification of four main geomorphological domains linked to major volcanic cycles. Moreover, we investigated and documented the potential of LiDAR intensity data for distinguishing and characterizing different volcanic products, such as fallout deposits, epiclastic sediments and lava flows.

Lidar surveys reveal eruptive volumes and rates at Etna, 2007–2010

The quantification of eruptive activity represents one major challenge in volcanology. Digital comparison of lidar-based elevation models of Etna (Italy) was made to quantify the volumes of volcanics emitted in 2007–2010. During this period, Etna produced several summit paroxysms followed by a flank eruption. We integrated the total volume difference resulting from the subtraction of the 2007 and 2010 digital elevation models with volumes of eruptive products based on field and aerial surveys to attribute volumes with hitherto unrealized precision to poorly constrained eruptions. The total erupted volume of 2007–2010 is >86 × 106 m3, most (~74 × 106 m3) of which is made up by the lava flows of the 2008–2009 flank eruption. The survey also reveals the high lava volume (5.73 × 106 m3) and average eruption rate (~400 m3 s−1) of the 10 May 2008 paroxysm, whose flow front stopped 6.2 km from the vent, not far from the town of Zafferana Etnea.

Rapid Updating and Improvement of Airborne LIDAR DEMs Through Ground-Based SfM 3-D Modeling of Volcanic Features

We present a workflow to create, scale, georeference, and integrate digital elevation models (DEMs) created using open-source structure-from-motion (SfM) multiview stereo (MVS) software into existing DEMs (as derived from the light detection and ranging data in the presented cases). The workflow also maps the root-mean-square error between the base DEM and the SfM surface model. This allows DEM creation from field-based surveys using consumer-grade digital cameras with open-source and custom-built software. We employ this workflow on three examples of different scales and morphology: 1) a scoria cone on Mt. Etna; 2) a lava channel on Mauna Ulu (Ki̅lauea); and 3) a flank collapse scar on Mt. Etna. This represents a new approach for rapid low-cost construction and updating of existing DEMs at high temporal and spatial resolutions and for areas of up to several thousand square meters. We assess the self-consistency of the method by comparison of DEMs of the same features, created from independent data sets acquired on the same day and from the same vantage points. We further evaluate the effect of grid cell size on the reconstruction error. This method uses existing DEMs as a georeferencing tool and can therefore be used in limited access and potentially hazardous areas as it no longer relies exclusively on control targets on the ground.