Musings on DEMs

  This shows the Sentinel-2 image overlaid on the Copernicus DEM. The ash clouds and clouds are plastered on the terrain, since the program has no information of their altitudes and only has the DEM.

A few years ago we spent spring break in the Canary Islands.  We were going to go to La Palma, but instead if Santa Cruz de la Palma, we wound up at Las Palmas to Gran Canaria.  We would up having a great time, but I don't have any pre-eruption pictures to go with the recent activity. Figure 1 shows the Sentinel-2 image from 26 August 2021, before the resumption of volcanic activity.  This is false color; the red is really near infrared (NIR) which is not the standard thermal imagery, but just light we cannot see and which vegetation reflects strongly.  This has 10 m pixels. Figure 2 shows the Landsat 8 image from September 26, showing the same color scheme but with pan sharpening to achieve 15 m pixels. There is ash trailing to the NE, and a lava flow going down the hill to west, with smoke or steam rising.  The lava flow itself is a thin red line, which is NIR energy which will be a mixture of reflected sunlight and heat emitted by the lava witch might be at 8...