Search

The 2021 Fagradalsfjall basaltic fissural eruption in Iceland was closely studied due to its proximity to Reykjavík, which allowed easy installation and maintenance of monitoring equipment. Here we present the results from a network of calibrated webcameras maintained by the Icelandic Meteorological Office and Department of Civil Protection and Emergency Management which were used to monitor volcanic plume height and fire fountain height. A number of different camera designs optimised for different power and communications constraints were used, some built in house at IMO, and they will be presented here. To make a 3D height measurement from a 2D web camera image requires extra geometric constraints, which are provided by assuming the vent location and wind direction, in a similar manner to the method applied at Etna. We have implemented this technique as a react.js single page app, which is kept updated by a messaging queue system which pushes new images through the servers at IMO. Additionally, the webcameras have to be calibrated, in that the geometry of the camera and lens distortion parameters have to be known - this is either perfomed in the laboratory, or where the cameras were not available before installation, using one of a number of vicarious calibration techniques developed for this purpose. The resulting plume heights were used to constrain SO2 dispersion models that were the basis for air quality forecasts during the eruption.

The Icelandic Meteorological Office (IMO) maintains a network of web cameras for monitoring the environment and identifying possible hazards, including reduced atmospheric visibility, changing river flow conditions and snow accumulation. Recently, the network has been expanded to improve the volcano monitoring capacity, with the specific aim of observing eruption onset and estimating volcanic plume heights. Here, we present how sites for cameras are chosen, the environmental constraints that inform the two camera designs currently in use, how the data is transmitted to the institute, stored, and pushed through the data processing system, and the different techniques used to calibrate the cameras and calculate the orientations of plumes such that measurements can be made from the images they produce. Camera calibration is a particular challenge for such a diverse range of cameras and environments, with some cameras already installed and inaccessible, and here we show how we use laboratory calibration, feature matching, horizon matching and star matching to find the internal camera geometry and camera orientation in different scenarios. Once calibrated, geometric measurements can be extracted from the images by either providing constraints from Numerical Weather Prediction (NWP) models on the likely orientation of the plume, or by using two images with different views, which provide enough information to pin down a point in three dimensions. In the latter case we show how ray projection can be used to locate a point. These plume calculation tools and final images are made available to the forecasters and natural hazard specialists on-duty using an interactive webpage. The plume height time series are easily saved for ingestion into the Volcanic Eruptive Source Parameter Assessment (VESPA) inversion system designed to assess eruption intensity and to provide calculated eruption source parameters in input to the tephra dispersion forecasting model.