Automated thresholding of active lavas using AVHRR data

An automated algorithm for thresholding hot pixels in AVHRR data is presented. The algorithm, applied to cloud-free sub-images of channel 3 minus channel 4 brightness temperature, compares each target pixel with its immediate background and then compares this difference with the natural variation in the surrounding region. Application to images of Mount Etna identified thermally anomalous pixels containing active lava or vents.