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Thinking about DEMS (Digital Elevation Models)

By

Jason Albert

Tune into digital elevation models and plan accordingly.

Tune into digital elevation models and plan accordingly.

Last week we focused on redundancy related to devices to communicate with emergency services absent cell service. That piece was a result of reflecting on personal practices and the January 4 avalanche on Togwotee Pass that took a life. That incident’s final report has been released. With the insights and analysis of the Bridger Teton…

Responses

  1. Ben Coffman

    In addition to field observations, there might be an opportunity for some skeptical map reading to identify inaccurate slope angle shading before ever entering the field. I’ve never noticed this before, but comparing the two images, it appears that while the slope angle shading is very different between the two, the underlying terrain shading (and topo lines) appear to be identical on both maps. It seems like the underlying terrain shading/topo lines can be used to identify areas where the slope angle shading just doesn’t make sense. This is especially demonstrated by the steeper slopes bordering the bottom of the drainage in the above images. While the steeper slopes bordering the drainage are not at all accurately reflected by the slope angle shading in image 1, they do still seem accurately reflected by the terrain shading and topo lines in image 1. Perhaps viewing slope angle shading with questions like “why has the shading not changed even though the topo line density has?” in the back of one’s head might allow for some advance identification of areas to confirm in the field.

  2. Chad Lorenz

    I found this video very useful when thinking not just about what the terrain looks like in the summer(LiDAR) but also that it can/will look different when covered. https://www.youtube.com/watch?v=nHdntjAiTok

    1. Jason Albert

      Thanks for linking to that Chad. I had forgotten about that video despite having written about it last season. (http://the-high-route.com/inclinometer-practice/). I’ll do a rewatch.

  3. Slim

    If they remotely triggered the avalanche from above themselves, and the polygon shows the extent of the avalanche, then I don’t see how the DEM is a contributing factor?
    Even the low resolution DEM shading shows the start zone is steep enough to produce an avalanche.
    Or am I misunderstanding something here?

    On the other hand, the top of the images show a very critical difference between the two resolution images.

    1. Slim

      Ok, in the report, they speculate that maybe the sidewall next to the lead skier was the initial start, and that is one of the differently shaded areas in the 10m vs 1m DEMs.

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