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

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?].

Differences between the Coxmate GPS and the NK Speedcoach GPS

NK Speedcoach GPS2 Coxmate GPS
GPS Yes Yes
Impeller Yes No
Programmable Workouts Yes Yes
Touchscreen No Yes
Clock Yes Yes
Data Recall Yes Yes
Rechargeable battery Yes Yes
Backlit Display Yes Yes
Course Recording No Yes
Voice Recording No No
USB Charger No Yes
PC Interface Yes Yes
Parameter Display Options Yes Yes
Mounting Options Yes Yes
Volume Level Save No No
Color Options Yes No
Playback Audio (through speakers) No No
Compact, Light Design Yes Yes
Waterproof Yes Yes
Buoyant No No
Rate 6-99.5 1-99.9
Speed Yes Yes
Distance Yes Yes
Time Yes Yes
Distance per Stroke No Yes
Stroke Count Yes to 999 Yes
Check Factor No No
Heart Rate Yes Yes
Average Speed No Yes
Speed Ratio No Yes
Navigation Assist No Yes
Workout Yes (Training Pack) Yes
Pace Boat No Yes
GPS update speed 5Hz 10 Hz
Configurable Functions
Stroke detection sensitivity No Yes
Averaging No Yes
Display Colour No Yes
Units (Meters, Kilometers, Miles) Yes Yes
Timer Auto Stop No 0-59:59.99 Yes


3 thoughts on “GPS comparison: NK, Coxmate, Minimax

  1. Pingback: Garmin Vivoactive HR for Rowing & Sculling - John R. Zaleski, Ph.D., CAP, CPHIMS

  2. Pingback: Tracking Rowing Data - how I do it • Rowperfect UK

  3. Pingback: In-boat force curves for rowing and sculling • Rowperfect UK

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.