My GPS Setup

TrailRunner screen shot

I often get asked about my GPS setup. Most of it actually happens off the water, so I figured I should provide a run down of all the bits and pieces, and how they work together.

I decided to purchase a GPS for a number of reasons...

Me windsurfing on my Tabou Rocket 145 with my Gaastra Matrix 7.5 sail

Firstly, you can't manage it if you don't measure it. When you are first learning you get used to getting passed by everyone, but as you progress you start to wonder what you can do better. If you don't have a way to measure the differences between runs, it can be difficult to figure out what is working and what isn't. Where should the mast track be? How high should you set the boom? Does closing the gap really make a difference? etc. This is where knowing your current, average and maximum speed come in handy - but you also want a wrist mounted device with a big display so you can get direct feedback while you are sailing.

Me getting a bearing from my wrist mounted Foretrex 201 GPS

Secondly, having a sense of where you are. Venturing out to sea can be quite intimidating. However if you have way-points and tracks from the previous legs you have travelled, it helps quash these fears. As the water gets darker and the shore looks further away, you can look down at your GPS and say, "I have been out further than this before". It also stops you from unknowingly drifting down wind on your outward legs.

It also helps to have a Personal Locator Beacon like the Spot GPS Satellite Messenger which I always take with me when I head out to sea [ you can read more about it here ].

An example graph of a speed run

Next, so I can compete with myself and others. While I may never be a contender on GPS-Speedsurfing.Com, I do get a buzz out of going fast, and comparing my results to my mates, and other speed sailors who turn up at Elliott Heads throughout the season. You need an approved GPS unit in order to get ranked, and it must be set it up to record tracks the right way in order for them to be valid.

An example of a session diary

Finally, to keep an objective diary of my sessions. This is a really cool feature of the TrailRunner software I use. I load the tracks from my GPS unit into TrailRunner and it shows me where I went, how far I travelled, how many runs I did, how fast I did them, and I can also record which board and sail I used and write a brief description of the day. This gives me a concise record of my sessions, allowing me to compare how good the conditions actually were and how well I performed. It also reminds me of which gear I used and in which conditions.

The Garmin Foretrex 201 GPS

Garmin Foretrex 201

This is the GPS unit I use, a Garmin Foretrex 201, which I purchased new on eBay. I chose this one for a couple of reasons. Most importantly because it only weighs 100g, so you can wear it on your wrist like a watch. This means you can interact with it on the water. Most of the other windsurfers I know use the GT11 or GT31, but these have to be kept inside an Aquapac (shown below) which is generally mounted facing out on their upper arm between their elbow and shoulder.

GT11 GPS in solder mounted Aquapac

As a result they can't see much of anything until they have finished their run. By comparison, the Foretrex 201 is waterproof and completely sealed so you can just ware it as-is. Most importantly at the time I purchased it it was a recently superseded model, so it was relatively inexpensive.


  • Small, rugged (with my mods) and light
  • Can be easily operated while sailing
  • You can customise the display
  • Has a choice of nautical miles (knots) as a unit of measure
  • Supports 2 second intervals for recording speed runs (its a GPS-Speedsurfing.Com approved device)
  • Has a countdown timer for racing, which helps get you in the right position before the starters horn


  • The wrist strap was way to small and the extension provided is dodgy (but this was easily fixed)
  • The moving average is tedious, you have to reset it every run
    • It would be nice if it logged a history of 10-sec averages
    • Instead I generally have to wait until I get home to find out how well I have done


To overcome the limitations of the wrist strap I did two things. I added a more substantial and permanent extension and an extra length of Velcro to make sure it never comes off my wrist on the water.

Garmin Foretrex 201 with extension sewn on the wrist strap

Above is the extension I added. The one supplied was made of elastic, and I wasn't happy with it, just another flimsy Velcro strap that could potentially fail for me to worry about. The extension I made is from a short length of webbing and a recycled stainless steel D ring from an old perished footstrap.

Garmin Foretrex 201 GPS with an extra length of Velcro sewn on the wrist strap

On the other end I sewed on an extra 5cm length of Velcro (red). Now the device has a reassuring snug and firm fit - even if it only fits on my wrist now - its going nowhere.

The setup

GPS-Speedsurfing.Com requires a 2 second interval.

  1. Turn on the GPS and press page until the menu appears
  2. Choose TRACKS
  3. Choose SETUP TRACK
  4. Set RECORDING to ON
  6. Set VALUE to 00:02

On the water

While these devices have been designed to store and organise lots of tracks (like trails and biking), the amount of data stored at 2 second intervals will pretty much fill the devices memory in one all day session. So you need to download your tracks after every session and clear the GPS memory before you head back out on the water. Store the tracks on your computer, not in the device.

You can customise the display too. I have found the most useful fields are MAX SPEED, SPEED, MOV'N AVG and TIME. There are other fields that would be very handy for sailors (of yachts) but they require more time fiddling with the menu than a windsurfer can manage. In particular I can see that getting bearings on way-points and velocity made good during races would be really handy.

Before each session

  1. Turn on the GPS and press page again until the menu appears
  2. Choose TRACKS
  3. Choose CLEAR TRACK and follow the prompts
  4. If you have saved any tracks, you should also choose DELETE ALL SAVED and follow the prompts
  5. Press page until the split screen appears
  6. Press enter and choose RESET MAX SPEED

By the way, I am told that saving tracks on this device is a no-no, because it trims the data. Its best to only use the active log.

Before each run

The device stores your speeds in memory. You can reset the MAX SPEED when you are sailing, so you can check it after every run.

  1. Press page until the split screen appears
  2. Press enter and choose RESET TRIP DATA, this will reset the moving average

Connecting to my Mac

Connecting this GPS unit to my Mac was probably the biggest headache, but now that I know how to do it, the process is actually relatively simple. The Foretrex 201 only has a serial interface (this has been resolved in more recent models like the 301 and 401 which have a USB interface), so I needed to get a USB-to-Serial converter.

A generic USB to Serial adapter

I purchased a generic USB-to-Serial converter on eBay from Hong Kong. At first it didn't work, but then I found out I needed a driver in order for it to be recognised by my Mac. The serial driver I needed for OS X was one that supported the Prolific PL2303 chipset (which I believe is the most common). The latest driver PL2303_1.2.1r2 can be downloaded directly from the Prolific web site.

You can check if your USB to Serial converter uses the Prolific PL2303 chipset by plugging the device in and going to System Profiler and checking the Hardware > USB section for a device called USB-Serial Controller. It should have a Vendor ID of 0x067b (Prolific Technology, Inc) and a Product ID of 0x2303.

The Foretrex 201 is a completely sealed unit with an external clip-on adapter

The Foretrex 201 is a completely sealed unit. It has little terminals on the back and an external clip-on adapter to provide a serial port and power connection for recharging the unit. The certainly makes the unit simple and robust - no little compartments with seals that might fail.

The Foretrex 201 with the adapter connected

The adapter simply clips on the back, and then you insert the serial connector, or power cable to recharge it. The serial cable was a bit stiff at first, so I really needed to push it firmly so that it is snug like you see above.

LoadMyTracks screen shot

Once all this is connected to my computer the final step is to upload the tracks. For this I use a simple utility called LoadMyTracks which works seamlessly with the import function in the TrailRunner software. You simply connect everything up, and click on the import icon in the toolbar and up pops the LoadMyTracks utility. The serial connection isn't super fast, but its not unreasonably slow either.

You should select "Garmin Serial" from the dropdown and "usbserial" as the serial port to use, then make sure the Foretrex 201 GPS unit is turned on and click "Acquire". The application will prompt you for a location to save the data and shows a progress bar while it is transferring the data. The Foretrex 201 GPS unit will beep and display "Transfer Complete" when its done.

Once I have the data, I generally delete the start and end bits before importing the data - this is where I am rigging, launching, then later retrieving and derigging my kit. I tend to leave my GPS unit on for most of the session because I also use it as a watch, so all the trips to the car and back end up in the track data. Obviously these things arn't worth keeping. With the data trimmed, I make a diary entry, I use the sail size for the diary type and the board for the equipment. That way at the end of the season, I can quickly see how many sessions I have used on each sail and board. If I have made a particularly fast speed run then I will select that specific run and save it separately. The time to do this is while you are importing tracks, there isn't a simple way to do it later.


All in all, for a the casual windsurfer like me, this is a great setup. It had a few kinks in the beginning, particularly with the wrist strap, but now that it is all sorted out I am really happy with the unit and the software I use with it. All up the total solution cost me less than $300 AU. I also really like the fact that I can interact with the device while I am on the water. Having to stop each time you want to look at a GT11 or GT31 that is obscured by an Aquapac would in my opinion be pretty tedious. That being said, if you were a hard-core speed-racer, you might just want the extra precision and features of these units, but for me, the setup I have is perfect.

Posted by Henry Thomas, 9 years ago on Wednesday, August 11, 2010


Claes said...

Hi Henry, I use a GT31 and it works fine to check the speed during a run/race. If the setup is done correctly the GT31 toggels between max speed and avg speed automaticly. Kind regards Claes

Posted 8 years ago on Sunday, July 24, 2011

Henry Thomas said...

Hi Claes,

I have no problem with the features of the GT31 unit (which in my opinion are superior to the Foretrex), just that in a Aquapac its a bit bulky and so most sailors I have seen using them wear them on their upper arm facing out. Their complaint to me was that they couldn't read data while they were sailing. In this regard the Foretrex has a clear advantage. Its small, light and works just like an oversized wrist watch.

Posted 8 years ago on Sunday, July 24, 2011

Rod said...

Does any one use the speed puck from velocitek?

Posted 7 years ago on Wednesday, November 23, 2011

Henry Thomas said...

Hi Rod,

No, I was not aware of the Speed Puck - it looks like a really cool unit. Only concern I would have is how and where you would mount it. I guess you could attach it to the mast above the boom, assuming there was enough space in the mast sleeve gap. Not sure if the units heading reading is effected by the unit turning, or just by changes in trajectory - if the former, rotating the rig, which you do constantly would give you erroneous heading readings - if the latter, then it would be a pretty interesting device for windsurfing.

It would be pretty cool having a speed on our mast, because you would see it all the time, because that is where you are facing most of the time.


Posted 7 years ago on Wednesday, November 23, 2011

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