Craig wrote, ......Wouldn't this only measure the acceleration of the paddle and not the kayak? Don't you want both to determine the efficiency of the paddle and the strokes? I actually do think that a paddlewheel-type velocity sensor would give you the best instantaneous data (if sampled quickly enough) which can then be compared to the GPS data. I've heard that some rowing coaches who will not use a GPS for training purposes because they cannot get that granular a data from any other method for the price..................... G'Day Craig, As I understand Matt is interested in measuring the drag on the boat and I don''t know if this requires both acceleration and velocity but both are available if needed as one can be calculated from the other because there is a time signal available. If a paddlewheel sensor is accurate enough it would be possible to measure an average velocity from the GPS accelerometer combination attached to the paddle by taking the integral of the acceleration signal against time, or by taking the derivative of the GPS signal; and then averaging the linear forward velocity. Re the triaxial unit we are trying, the video only shows angular motion and no hint of linear motion detection and the link to the spec sheet is unavailable hence our need to test it. We'll also try the GPS accelerometer combination where we know we can derive a signal. Regarding the paddlewheel, I misunderstood your comment earlier but note the error in two paddlewheel specs I've checked is 2cm/s. If a paddlewheel sensor is accurate enough then they often come with magnets to pass a pulse signal through the boat so this could be time liked to the paddle signal by installing a blue tooth chip in the paddle. I would expect it would be as accurate as deriving the average forward motion from an accelerometer attached to the paddle but not from a separate accelerometer attached to the boat rather than the paddle, provided you changed the data rate code on the boat accelerometer chip which at present is set to 1 Hz. All the best, PeterO *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Sun Aug 01 2010 - 14:10:36 PDT
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