Retrieval of absolute SO<sub>2</sub> column amounts from scattered-light spectra – Implications for the evaluation of data from automated DOAS Networks
Abstract. Scanning Differential Optical Absorption Spectroscopy (DOAS) networks using scattered solar radiation have become an increasingly important tool for monitoring volcanic sulphur dioxide (SO2) emissions. In order to get absolute column densities (CDs), the DOAS evaluation requires a Fraunhofer Reference Spectrum (FRS) that is free of absorption structures of the trace gas of interest. At volcanoes, this requirement can be formulated in a weaker form, if there is a plume free viewing direction within the spectra of a scan through the complete sky. In this case, it is possible to use a specific viewing direction (e.g. zenith) as FRS and correcting for possible plume contamination in t…
A new method for the identification of archaeological soils by their spectral signatures in the vis-NIR region
Abstract This paper introduces a statistical method to identify spectral signatures of buried archaeological remains and distinguish them from spectra of the background soil in the visible to near infrared region. The proposed method is based on the Principal Component Analysis (PCA). The difference between an archaeological spectrum and non-archaeological soil spectra is quantified by a so-called R value. R values larger than 1 indicate that the spectrum represents an archaeological material. The method is successfully applied to samples from five study sites in Italy and Hungary with special conditions. The reflection spectra are taken in a time-efficient way with a field spectrometer. Th…