Calibration of aerial thermal infrared imagery for walrus population assessment

Abstract

Concurrent aerial photography and emitted thermal infrared (10.6μm) imagery were acquired over walrus hauled out on sea ice in Foxe Basin, Northwest Territories, Canada. Digital thermal infrared data from a Forward Looking Infrared (FLIR) imager provides a method for estimating walrus numbers, since the objects (walrus groups) are considerably warmer than the background (ocean and sea ice). Coincident photographic counts and thermal infrared pixel counts are regressed by means of a least squares linear regression and an estimate of group size predicted from the number of pixels represented by each group. -from Authors