TY - CONF

T1 - Determining the rheology of active lava flows from photogrammetric image sequence processing

AU - James, Michael

AU - Robson, Stuart

AU - Pinkerton, Harry

PY - 2010

Y1 - 2010

N2 - We describe a photogrammetric approach used to determine the rheological properties of active lava flows based on stereo image sequences. Bulk rheological properties can be estimated from measurements of flow slope, velocity and dimensions and so, at flow-fronts, they can be calculated fromsequential digital elevation models (DEMs) acquired as the flow advances over new ground. For useful flow parameters to be extracted, DEMs may need to be obtained at approximately minute intervals, over durations of up to multiple hours. To deliver such data, we use oblique stereo pair sequences captured bydigital SLR cameras and a semi-automated DEM-generation pipeline. Although similar data could be acquired with a terrestrial laser scanner, with deployments in remote and hazardous regions the photogrammetric approach offers significant logistical advantages in terms of reduced equipment cost, bulk,weight and power requirements.We describe the application of the technique to an active lava flow on Mount Etna, Sicily, in 2006. Image sequences were acquired from two tripod-mounted cameras over a period of ~3 hours, as the flow-front advanced ~15 m. Photogrammetric control was provided by 11 targets placed in the scene, with their coordinates determined by dGPS. The cameras were synchronised by a shutter release cable and triggered by an external timer (intervalometer). Image pairs were obtained every minute with DEMs extraction carried out on every fourth epoch; 57 DEMs, with a 0.25-m resolution, were generated.We describe the challenges associated with data collection in this remote environment and the techniques required to automate the photogrammetric analysis and sequence-DEM generation.

AB - We describe a photogrammetric approach used to determine the rheological properties of active lava flows based on stereo image sequences. Bulk rheological properties can be estimated from measurements of flow slope, velocity and dimensions and so, at flow-fronts, they can be calculated fromsequential digital elevation models (DEMs) acquired as the flow advances over new ground. For useful flow parameters to be extracted, DEMs may need to be obtained at approximately minute intervals, over durations of up to multiple hours. To deliver such data, we use oblique stereo pair sequences captured bydigital SLR cameras and a semi-automated DEM-generation pipeline. Although similar data could be acquired with a terrestrial laser scanner, with deployments in remote and hazardous regions the photogrammetric approach offers significant logistical advantages in terms of reduced equipment cost, bulk,weight and power requirements.We describe the application of the technique to an active lava flow on Mount Etna, Sicily, in 2006. Image sequences were acquired from two tripod-mounted cameras over a period of ~3 hours, as the flow-front advanced ~15 m. Photogrammetric control was provided by 11 targets placed in the scene, with their coordinates determined by dGPS. The cameras were synchronised by a shutter release cable and triggered by an external timer (intervalometer). Image pairs were obtained every minute with DEMs extraction carried out on every fourth epoch; 57 DEMs, with a 0.25-m resolution, were generated.We describe the challenges associated with data collection in this remote environment and the techniques required to automate the photogrammetric analysis and sequence-DEM generation.

KW - lava

KW - rheology

KW - photogrammetry

KW - Etna

M3 - Poster

ER -