<jupyter_start><jupyter_text>Practical 3: Dgital Elevation ModelsIn this practical, we'll make visualizations and calculate derived quantities of LiDAR DEMs of the Kīlauea volcano on the Big Island of Hawai'i. The DEMs cover the main volcano summit and the Halemau'mau crater from before and after the [2018 lower East Rift zone eruption](https://www.usgs.gov/volcanoes/kilauea/2018-lower-east-rift-zone-eruption-and-summit-collapse).[![Aerial photo of Halemau'mau crater and part of the Kīlauea caldera taken on July 13, 2018](https://prd-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/thumbnails/image/img6670.jpg)](https://www.usgs.gov/media/images/aerial-view-k-lauea-summit-july-13-2018)*Aerial photo of Halemau'mau crater and part of the Kīlauea caldera taken on July 13, 2018. The buildings housed the USGS Hawaiian Volcano Observatory and Hawai‘i Volcanoes National Park's Jaggar Museum. Source: [USGS](https://www.usgs.gov/media/images/aerial-view-k-lauea-summit-july-13-2018) (public domain).*  Import the required librariesWe'll start by importing the things we'll need to load the images, do some calculations, and plot them.<jupyter_code>import skimage.io
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.colors import LightSource<jupyter_output><empty_output>
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