Fig. 2
From: Automated tracking of lava lake level using thermal images at Kīlauea Volcano, Hawai’i
Segmentation approaches for isolating the lava lake in the thermal images and measuring its level. Images taken November 23, 2012. a. One of the original images in two minute block of images used to construct the subsequent binary images in this figure. Image from November 23, 2013 03:00 HST. b. Composite image generated from individual binary edge detection images from the 24 image block of data (two minutes). c. Composite image constructed by taking the maximum temperature at each pixel location within a 24 image block of data, and then thresholding at 300 °C. d. Standard deviation calculated at each pixel through a two minute block of time, and thresholded at 40 °C. e. Summed image from the three approaches, with colors denoting the sum (0–3) for each pixel. A pixel value of 3, for instance, indicates that all three binary images have a value of 1 at that location, while a pixel value of 0 indicates that none of the three images have a pixel value of 1 at that location. On the right side is the profile (f) constructed by summing pixels in each row in the swath of the image. An empirical threshold is then used to locate the boundary of the lake against the crater wall