Abstract
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, 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 method by means of a uniquely designed indoor analog experiment. A volcanic hotspot 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 over the mid-wave infrared to the thermal infrared. In the conducted experiment, the hotspot’s pixel fraction was successively reduced by increasing the camera-to-target distance from 2 m to 38 m. We carried out three experiments with three different wire temperatures: 700 K, 920 K, and 1050 K. The estimated relative deviation between the observed and theoretical hotspot's pixel fraction is within 20 % for most distances. The estimated temperature of anomaly has stronger fluctuations.
Highlights
The discipline of satellite thermal remote sensing provides physical insight into the processes governing volcanic activity and has become a valuable tool of vol− canology since the pioneering paper on the topic was published [Gawarecki et al, 1965]
FieldSpec Pro (FS) is provided with a bare fiber optic and a conical field of view (FOV) of 35
As we had emissivity observations available only for the short−wave infrared (SWIR) spectrum, we had to determine the emissivity of the metal alloy in the mid−wave infrared (MIR) and thermal infrared (TIR) differently
Summary
The discipline of satellite thermal remote sensing provides physical insight into the processes governing volcanic activity and has become a valuable tool of vol− canology since the pioneering paper on the topic was published [Gawarecki et al, 1965]. The volcanological community is confronted with the problem, that none of the currently operational satellite sensors have been designed primarily for volcanological purposes. Conse− quently, the available data, mostly from meteorological satellites, is not ideal for volcano surveillance in two ba−. The satellite orbits are not well adapted, affecting the satellite volcano viewing ge− ometry and temporal resolution. Apart from these data limitations, there is the general difficulty that the radi− ance measured by the sensor differs from the radiance emitted by the ground heat source, mainly due to surface emissivity, atmospheric and geometric influences
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