Measuring light attenuation with a compact Optical Emission Spectrometer and CTD mounted on a low cost AUV

We use an AUV, Starbug, to produce habitat maps by identifying benthos from their spectral signatures. This requires a measurement of the light attenuation in the water column at the current site. The study area usually contains two layers of water with distinct attenuation characteristics, which can vary substantially in response to events such as algal blooms and floods. Therefore it is necessary to calculate the attenuation characteristics on each deployment. Here we present a methodology that uses a simple spectrometer to determine the attenuation characteristics in the course of a regular mapping deployment. The statistical framework used permits reliable results to be obtained from a low quality instrument in extremely variable environmental conditions.