ASSESSMENT OF THE DUAL-BAND METHOD BY AN INDOOR ANALOG EXPERIMENT

The evaluation of infrared satellite images over active lava flows assists the identification of potentially threatened areas and thereby the overall lava inundation hazard assessment. The estimation of the lava flow's size and temperature is not trivial as the lava occupies only a small fraction (< 1 %) of a typically resolved target pixel (e.g., from Landsat 7-ETM+; EOS-MODIS). Conventionally, this is solved by processing observations in at least two separate infrared spectral wavebands. We investigate the resolution limits of the Dual-Band (DB) method by means of a uniquely designed indoor analog experiment. A volcanic thermal anomaly is simulated by an electrical heating alloy of 0.5 mm diameter installed on a plywood panel. Satellite observations are simulated by two thermographic cameras with wavebands comparable to those available from satellite data. These range from the short-wave infrared (SWIR) over the mid-wave infrared (MIR) to the thermal infrared (TIR). In the conducted experiment, the hotspot's pixel fraction (p) was successively reduced by increasing the camera-to-target distance from 2 m (p = 41.7 %) to 38 m (p = 2.2 %). We carried out three experiments with different wire temperatures and compare different DB setups. In the case of the hottest wire (1019 K), the standard method gives relative deviations between the observed and theoretical hotspot area fractions below 16 % for about one third of the cases (i.e., distances).