Tuesday, October 28, 2014

Daily averaging of coastal time lapse photos

Time lapse of the toe of the Ledgewood Slide on Whidbey Island. Photos collected every 30 minutes between April and June 2013

I've posted numerous times about the value of photography for understanding coastal systems, and in particular like time lapse photography. Time lapses of the coast are invariably interesting and contain lots of information, but one thing that has always bothered me about time lapse on the coast, though, are the problems associated with both changing lighting throughout the day, as well as changing water level. Both make it very hard for the eye to track the morphological change that is often my interest in collecting the photos in the first place.

The video above, composed of time lapse photos collected every 30 minutes, provides a great example. The interest here was in understanding when, and how much the toe of a coastal bluff failure on Whidbey Island, eroded over the year after the slide. In this case there is observable change, but its hard to track with the eye due to changing light and water level. Here is another example:

Time lapse of Hollywood Beach, Port Angeles, composed of photos collected every hour between December 2013 and June 2014

In this case I was interested in understanding the timing of the on-shore movement of the big piles of Ulva lactuca that appear on Hollywood Beach (in Port Angeles, Washington) every winter. Here, the problem isn't so much lighting, but the length of the video is a bit imposing.

So I took a cue from Andy Ritchie at Olympic National Park, who came up with the idea of AVERAGING all of the time lapse photos taken over the course of a day to create a series of much-viewed time lapses of the removal of dams on the Elwha River. Of course! By averaging all of the time lapse photos collected over a day the variations in light and water level are largely eliminated, and the coastal change of interest is highlighted. Here are the same two time-lapses shown above:

Daily average time-lapse of toe erosion on the Ledgewood Slide, Whibey Island

Daily average time-lapse of Hollywood Beach, Port Angeles, during the winter of 2013-2014 showing the on-shore movement of pulses of Ulva lactuca

The downside in my mind, is that some of the daily average photos are a bit blurry - probably due to wind causing the camera to move ever so slightly. A better camera mount should solve this problem, but often times my camera placements are temporary and utilize whatever structure I can find on the beach. Despite this problem, though, I think the result works. Any thoughts from readers would be appreciated.

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