Sunday, October 30, 2011

GPS Speed Talker

Regular readers of my blog may have noticed that I like to know how fast I'm going when I am windsurfing. So I was quite intrigued when someone mentioned the idea of using a smartphone to not only measure your speed, but announce it to you while sailing. My biggest concern was that the "waterproof" bags I had been using for my GPS unit all started to leak after a few sessions. That's no problem with the GT-31 device I am using, since it is sufficiently waterproof to tolerate a bit of water in a bag (but not a high speed crash while windsurfing). But with an iPhone or android phone, the same amount of water would have ruined a pretty expensive piece of equipment.

Still, the idea stayed in my head. The fact that the windsurfer who mentioned, Roo, it had helped develop the "standard" GPS unit (the GT-31), helped keeping it there - as did the fact that Roo managed to get an average speed rating of 40.2 knots in the Gorge, and is currently listed as the 3rd fastest windsurfer in the US on  I actually got a little "Speed Talker" app for my iPhone that announces GPS speeds - but when I tested it while driving around, I noticed a 5-10 second delay between speed changes and the announcement of the new speed by the app. It seems like the app uses too much dampening to eliminate spikes in the GPS data. After that, I gave up on the idea for the time being.

But two weeks ago in Hatteras, I needed to buy a new waterproof armband for an extra GPS that I had brought along. I got lucky at Wind-NC, where Andy had a DryCase waterproof armband for $40, about the same cost as the the AquaPac armband I had been using. Here's an image:
Well, this bag had a headphone connector! I also liked the idea that it is vacuum sealed. This allows you to see if a bag has a leak before you hit the water. But perhaps more importantly, the vacuum creates a static cling between the plastic around the phone, and the phone and the plastic. When you open the bag after vacuum sealing it, you actually have to pry the plastic apart. I believe that this is a much better solution than regular waterproof bags that keep air on the inside: if you immerse a bag with air into water, the outside pressure will be higher than the pressure in the bag, pushing water into the bag through any little hole there may be. I think that the water intrusion in a DryCase bag will be a lot less even when the bag has a hole.

So for a GPS-loving windsurfing geek, the rest of the story is pretty predictable. I used the bag once or twice with my iPhone (which I had wrapped into a ziplock bag for extra safety). It worked, but I found the delay between actual speed changes and the announcements too irritating. Imaging having just fallen into the water, and the Speed Talker app tells you that you are still going at 20 knots!

So I did a bit of research for alternative apps, and discovered GPS Speed Talker. The great thing about this app is that it was developed by a speed surfer for GPS speed surfing. However, it is only available for android phones. But then, if you are really concerned about using an "officially approved" GPS unit, the app can actually tell you the speed that a GT-31 unit with bluetooth (a BGT-31) measures!

The next stop was to the local Best Buy. In the "No Contract" section, they had Android phones with GPS starting at  $89.99. I opted for an LG Optimus V for $129.99 because the provider (Virgin Mobile) offered a cheaper plan ($35/months for including web, messaging, and 300 minutes talk time). I don't have plans to activate the phone right away, but I might just do so in the future (and save about $30 per month compared to my current iPhone plan). Note that the phone is about $20 cheaper than a GT-31!

I tried the setup yesterday in a cold and rainy Nor'easter. Before going out, I had tied a piece of bright foam to the arm band - I have had arm band come off while sailing before, and the bag without any air in it would sink (or at least it did sink when I tried it in the kitchen sink). It worked quite well at first. But later, the wind picked up, and I had a number of falls, sometimes loosing the ear buds. It got pretty loud, too, between the wind, the small waves hitting the board, and the rain. After a while, I did not hear the announcements anymore, perhaps because some water had gotten into the earbuds. A bit later during a swim or waterstart, my arm caught the wire, and pulled the earbuds out of my ear, and the connector out of the housing. I just stuffed the ear phones into my neoprene hood, sailed to shore, and then put them into my dry suit. The ear buds I had used where also from DryCase ("DryBUDS", $29.99), because that't what Wind-NC had in store. They come with 3 different sizes of ear buds; one of these fit well enough on land, but eventually came out. I think I'll have to try different kinds of waterproof headphones - there are many available on, starting at $15, and the reviews from swimmers seem helpful.

When I got home, I wanted to compare the tracks from the GPS Speed Talker app with the tracks from the GT-31. However, I discovered that I had forgotten to press the "Start logging" button in the application, so there was nothing to be exported. I guess I am just to used to the GT-31, which automatically starts logging when you turn it on.

So yesterday's test of the GPS Speed Talker / android phone setup was only a mixed success. The conditions where at first too gusty, and then changed too quickly to survival-mode sailing, to allow me to try what I wanted to do: see how small changes in stance, angle, etc. would affect speed, with instant feedback. How crazy did it get yesterday? Well, let's see how the various members of the Fogland Speed Surfers team fared:

  • Nina went out on a 77 l board with a 4.5. At first underpowered in lulls and overpowered in gusts, then mostly overpowered. Had the smarts to stop before things got out of hand. Never made it all the way to the far shore where the water was flattest, so she did not get any good top speeds.
  • Dani had the bad luck of trying my 5.0 GPS sail, which I had rigged on a mast that just did not work for the sail. The sail was way too twitchy. Without a dry suit, Dani was quickly too cold and overpowered and stopped sailing. 
  • I made it to the other shore and did some speed runs in the flat water there. However, it was quite gusty close to shore, and the wind direction was a bit wrong - as the tide went out, the wind was partially blowing against the current, so it was not flat enough. When sailing away from shore, the swell/chop got bigger very quickly, so downwind runs were not really an option, either. My top speed was about 28 knots, which I found quite disappointing for the conditions. My nautical mile average of 24.17 knots was ok, though (my second-best ever). I later did a few runs on Dani's iSonic 86 with the GPS 5.0 sail, but with the wrong mast, it was harder to sail than the GPS 6.6, and I got nowhere close to getting near top speed on the board.
  • Dean is the fastest sailor in our little group, and often hits 35 knots if the conditions are right. He started late using his 6.7 m sail, but stayed out until dusk. He did not find any flat water for downwind runs, and was way overpowered towards the end, with half-frozen fingers since he had ditched his gloves early on. He did not reach any speeds that he found worthwhile posting.
  • Nikita is the second-fastest surfer in our group, and by far the best freestyler. He came even later, and rigged a beautiful 5.5 m GPS sail. Seeing his sail rigged made it very clear how badly the mast worked for my 5.0! Nikita is about 20% lighter than Dean and I are, so he was overpowered on the 5.5. He used gloves, which however killed his forearms in no time. He also did not reach speeds he found worthwhile posting.
  • Graham was the one windsurfer from our group that always seemed fully in control on water.  He was out on 4.4 at first, and later switched down to 4.0. He looked quite fast, but he was working on freestyle, and was not wearing a GPS. 
Recently, we got what we wished for - we wanted lots of wind, and got so much that even the best windsurfers in our groups were a bit overwhelmed. So maybe we have to formulate our wishes a bit more clearly: wind in the upper 20s, gusting into mid-30s, from NE or SW, without rain and with air temperatures above 50. Please?

1 comment:

  1. atcGreat to see you trying out the speedtalker app. I set the readout to kmh instead of knots, you get a faster update and readout rate so you can hear more changes in speed. The H2O headphones work really well for me. I'm experimenting with a 10hz GPS linked via Bluetooth, will let you know if it's any good.