Tunnel Vision

People have limited memories, so we rely on recorded information to help us.  After awhile we have so much information that we can’t cope, all that information becomes noise.  In response we have created tools to filter and manipulate the noise.  Problem is that filtering and manipulation can easily result in misinterpretations of the results.

Imagine viewing the world through a long black  pipe.  Depending on where you point the pipe, the world could be all green or all blue.

Environment Canada issues a monthly publication available on-line, LEVELnews.  The December issue Volume 10, Number 12, contained some grim statistical data.  Using that long black pipe to view water levels can be very misleading.  A single moment compared to a year ago could easily lead to a “sky is falling” view. In this case December 1st is reported 42 cm below the same date a year ago.  The graph below shows the problem with using “year ago” statistics.  The bottom line is 2012, the top 2011, in the middle is 2009 and 2010 (the y axis is water level relative to chart datum, x axis is in hours).

Again our field of view is important, this windows shows a low of .6 meters at the beginning of December.  If we include more days either side of the 1st, we see that a major dip had actually occurred, the term for this is a Seiche.  It can be caused by a variety of environmental influences, wind, barometric pressure, and tidal.  The lowest point on this graph just happens to be the 1st of the month.  If this graph were shifted a few days on the calendar, water levels for the beginning of the month wouldn’t be so scary, and in-line with 2009, 2010 levels.

In the end water levels are low. Is this a good thing or a bad thing, the experiment continues.  Data for graphs is from the Science archives of Fisheries and Oceans Canada and is available to the public for none commercial use.


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