GPS comparison: NK, Coxmate, Minimax


Using GPS for boat speed has limitations.  One of the main ones is the speed the unit updates based on the GPS satellites.

This is determined by the clock speed in Herz.

  • NK uses a 5 Hz chip which is 5 times per second update cycle.
  • Coxmate has a 10 Hz chip which is 10 times per second.

The faster speed gives improved position control especially at slower speeds (like rowing boats).

Garmin says about its product which also uses 10 Hz update chip

Observable Advantages

Compared to devices with slower update rates, GPS 19x offers dramatic improvement when used at low speeds. Position and course information from slower devices can jitter and swing considerably at speeds below 1 mph. The GPS 19x provides a consistent and smooth heading which is especially important when trying to hit a specific waypoint or mark.

So I went deeper into comparing different applications for rowing use

Compare NK, Coxmate and Catapult Minimax

I was listening to Greg Hughes being interviewed by Joe DeLeo about using technology and he recommended a product call the Catapult Minimax.  Which I’d not seen before.

The 3 pieces of technology Greg uses focus on heart rate variability, measuring the force curves and the GPS to track boat speed and check.

  • FirstBeat Heart Rate system monitors HR and HR variability and shows it in real time.
  • Peach System force curve instrumented oarlock measuring force and length of the stroke by person in the crew. slip at the catch and finish, when they reach peak force and force curve alignment.
  • Catapult Minimax a high powered GPS collects data 100 times a second to see the way the boat accelerates and decelerates showing boat check (pitch /roll / yaw), fine tuning the boat movement.

Minimax Rowing GPS Minimax Rowing GPS

Minimax Rowing GPS Minimax Rowing GPS[/caption]

When I sent this over to the Coxmate team, they told us about the development of Minimax for rowing.

The Catapult Minimax was initially produced in conjunction with the Australian Sports Commission.  It is mainly driven by field sports, primarily Aussie rules football here.I have the previous generation Minimax that I used extensively for several years.  In summary the Coxmate GPS is a waterproof version of the Minimax with a touch screen for one tenth of the cost.  The only thing that is better about the Minimax is the software Rowing Australia use which is just as insightful as ours but produces more comprehensive reports.  Our recent improvements to the software have brought us much closer to their reporting.

The only thing the Minimax has that we don’t is the gyroscopes.  The Rowing Australia software uses these to model 3D renderings of the boat in motion which is very cool to see but almost impossible to apply as a coaching tool.  I use my eyes or a video camera to achieve the same thing!

Differences between the Coxmate GPS and the Minimax

  • Cost (AU$):  $340/$3000+
  • Waterproof:  Yes/No (hence the Tupperware container in the images)
  • Software:  Rowing specific/non specific (Rowing Australia developed their own software that is not available to general public)
  • Screen:  Colour/touch/Not applicable in Minimax
  • GPS Chip:  10Hz/10Hz
  • HR:  Yes/Yes
  • Accelerometer:  Yes/Yes

It is crazy that we sell something at one tenth the price that is actually better.  [Well we would say that wouldn’t they?].


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