G'Day Matt, As promised here are some suggestions for measuring instantaneous kayak velocity. I looked at infrared golf swing meters and ultrasound doppler fetal monitors and they are certainly cheap enough and accurate enough but would need a fair bit of modification. Likewise as Craig pointed out, impeller knotmeters and GPS are not accurate enough. However, as we discussed it should be possible to measure average velocity and then use it to correct for drift in the 'instant' velocity derived from the accelerometer. I then asked my mate Andrew Eddy, who is very skilled at finding useful control electronic devices, if there were such a thing as a bluetooth accelerometer so we could easily link it to a computer and correct for drift off line. He found someone who sells all the necessary parts as a system. Bluetooth GPS devices-logs GPS and acceleration at 1Hz and 10Hz respectively. http://www.oceancontrols.com.au/GPS-030.html So in one unit you could get fast accelerometer data and slower GPS data to correct for drift They also sell a combined gyro, accelerometer, magnetometer, with three-axis measures of each, that can connect to a blue tooth modem. http://www.oceancontrols.com.au/SFG-009.html i Bluetooth modem http://www.oceancontrols.com.au/WIR-010.html As you will see from the Youtube video of the 9-axis unit its just what Andrew and I are after for measuring blade movement in rolls and sweeps and it might be interesting if you wanted to combine boat pitch roll and yaw with the paddle signal http://www.youtube.com/watch?v=WuHRCnpcsDQ Andrew and I have ordered the 9 axis unit so I'll be able to try out a velocity algorithm and tell you whether you need the combined GPS/accelerometer or whether the 9axis unit and modem will do the job. GPS/accel logger $200 9-axis devices $119 Bluetooth modems $77 Usual waivers I don't have any financial interest in either Talon or Ocean Controls. Hope this helps, 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/ ***************************************************************************
Thanks, The Bluetooth GPS device might be able to be used (attached to the Talon paddle) to match in time (stroke for stroke) the angular data from the Talon paddle's built in sensors and then we could know the kayak's speed via this Bluetooth GPS devices GPS at the same time the Talon paddle was providing drag measurements in the direction the kayak was moving with its built in strain guages. > Date: Fri, 30 Jul 2010 11:46:38 +0000 > From: rebyl_kayak_at_energysustained.com > To: marinerkayaks_at_msn.com; paddlewise_at_paddlewise.net > Subject: Suggestions for kayak velocity measurements > > G'Day Matt, > > > > As promised here are some suggestions for measuring instantaneous kayak velocity. > > > > I looked at infrared golf swing meters and ultrasound doppler fetal monitors and they are certainly cheap enough and accurate enough but would need a fair bit of modification. Likewise as Craig pointed out, impeller knotmeters and GPS are not accurate enough. However, as we discussed it should be possible to measure average velocity and then use it to correct for drift in the 'instant' velocity derived from the accelerometer. > > > > I then asked my mate Andrew Eddy, who is very skilled at finding useful control electronic devices, if there were such a thing as a bluetooth accelerometer so we could easily link it to a computer and correct for drift off line. He found someone who sells all the necessary parts as a system. > > > > Bluetooth GPS devices-logs GPS and acceleration at 1Hz and 10Hz respectively. > > http://www.oceancontrols.com.au/GPS-030.html > > > > So in one unit you could get fast accelerometer data and slower GPS data to correct for drift > > > > They also sell a combined gyro, accelerometer, magnetometer, with three-axis measures of each, that can connect to a blue tooth modem. > > http://www.oceancontrols.com.au/SFG-009.html i > > > > Bluetooth modem > > http://www.oceancontrols.com.au/WIR-010.html > > > > As you will see from the Youtube video of the 9-axis unit its just what Andrew and I are after for measuring blade movement in rolls and sweeps and it might be interesting if you wanted to combine boat pitch roll and yaw with the paddle signal > > http://www.youtube.com/watch?v=WuHRCnpcsDQ > > > > Andrew and I have ordered the 9 axis unit so I'll be able to try out a velocity algorithm and tell you whether you need the combined GPS/accelerometer or whether the 9axis unit and modem will do the job. > > > > GPS/accel logger $200 > > 9-axis devices $119 > > Bluetooth modems $77 > > > > Usual waivers I don't have any financial interest in either Talon or Ocean Controls. > > > > Hope this helps, 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/ ***************************************************************************
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