Guest Post: Tracking a runner in the Boston Marathon with the Garmin GTU 10

Note from Ray: Last week leading into the Boston Marathon I had a reader (John) that e-mailed me asking if I’d like to follow along his wife’s progress on the day using the new Garmin GTU 10 tracker. As he explained his plan, I immediately realized this would be an amazing guest post.  I think you’ll really love the creativity and thoroughness of John’s post!

Last fall my wife registered for Ironman Wisconsin, which is in September 2011. So when Garmin introduced the GTU 10 in January I was intrigued. I’ve often worried that she would crash on a long training ride and end up unconscious in the ditch, leaving the Gucci new tri bike unguarded at the side of the road. For those of you unfamiliar with the Garmin GTU 10 it is a tracking unit that combines GPS and cell phone technology to allow people to track the location of the unit via the internet. The main reason I purchased the GTU 10 was to be able to track my wife’s location while she completes her training runs and rides. So far, I can say that it has been very useful both in the practical sense of knowing where she is and when she will be home and in the financial sense of knowing when she goes to Starbucks.

One of the interesting features of the GTU 10 is the ability to set up geofences. Geofences are boundaries that you can draw on a map via the Garmin website to define areas of interest. Depending on how you set them up, you will get a text or email notification when the tracker enters or exits the boundary. The idea behind the geofence, for example, is that you could put the tracker in your kid’s back pack and you would get an email when he enters the geofence that you have drawn around his school. In a similar fashion, I get emails every time my wife goes to the Starbucks near our house. This enables me to call her on her cell phone to find out what’s wrong with the coffee maker at home. So far the GTU 10 has paid for itself in coffee savings alone.

Boston Marathon 2011

Fast forward to last weekend where my wife was running in the Boston Marathon. I’ve had the opportunity to watch my wife run in several marathons and it has always been difficult to get information on how she is doing from a pacing standpoint. In some races, like the Chicago Marathon, the race organizers offer text updates of runner location and pace, but in other, smaller marathons, there are no such updates. The problem is that even in the races where there are text updates, the cell networks tend to get overtaxed on race day and the updates tend to lag or not come through at all. In most cases you have no idea how your runner is doing until the race is over. This got me to thinking, “Could one set up geofences to send text or email messages when the runner crosses certain checkpoints in the race?”. So I set out to give it a try.

Each Garmin GTU 10 basic account allows the user to set up 10 geofences. Initially, I reasoned that this would allow me to track my wife at 10 locations throughout the race. After a little bit of thinking, however, I realized that the tracker will notify you when the device enters and or exits a geofence. Bingo, I thought, this will allow me to get splits at 20 locations throughout the course. While this was good, my pea brain was having difficulty trying to figure out the best way to split 26.2 miles in 20 locations. Finally, I realized that each geofence can be set up to contain a maximum of 10 points. By using some creativity when drawing a geofence, you can get up to 10 notifications per geofence. Even with my basic math skills it was evident that I could get more notifications than I could use. Armed with an adequate number of geofence boundaries, I decided to set up notifications at each mile marker.

The first challenge was determining where each mile marker was on the Boston Marathon course. This was easily solved by logging on to, searching for a Boston Marathon route, and choosing one of the many that were listed. The image below is the one I selected.

MapMyRun Boston Route

By clicking on the expand button in the upper right hand corner of the image you get a more detailed view with mile markers at each mile. I then used the map controls to zoom in on each mile marker. It is important to zoom in far enough that you can locate the mile marker based on the information on the map like cross streets, lakes, rivers , etc. I did this for each mile marker and printed out a screen shot for future use. Below is a typical screen shot from mile 22 and a screen shot at roughly the same scale from the finished geofence from the Garmin website. You can see from the images below that the geofence crosses the marathon route in the same location as the mile 22 marker from the image on the right.

Creating Geofence at Mile 22Creating Geofence at Mile 22

After writing most of this post, I began to wonder how accurate my geofences were relative to the actual mile markers on the course. To make a long story short, I remembered that the starting line is painted on the street in Hopkinton. The Garmin software has the option of drawing the geofence on a map or a satellite view. Below is an image of the geofence I drew at the start line (before I knew it was painted on the street). The photo scale is shown at the bottom of the drawing. As you can see, I am only about 15 yards off the actual start.

Boston Marathon Start Line Satellite

Armed with screen shots from the start and each mile marker, I set out to define my geofences on the Garmin site. As I stated above, I was able to get creative with the shapes of the geofences so that I could get up to 9 splits from each geofence. As you can see below, a simple square shaped geofence will yield 2 notifications while a more creatively shaped one can yield many more. All you have to remember is that a geofence can be defined by no more than 10 points. The red dots in the images below represent locations where the GTU 10 will send a geofence enter/exit notification. The red line represents a typical race route.

A Square GeofenceAn Optimized Geofence

For the most part I set up each geofence to provide four notifications, two entrances and two exits. Below is a screen shot of the geofence that I set up for miles 19-22 along with the section of the Boston Marathon Course from

Boston Marathon Miles 19-22Boston Marathon Miles 19-22 Geofence

I repeated this process to map out the entire course. You will notice that I forgot to set up a geofence at mile 2.

Boston Marathon Geofences

In addition to the mile marker splits, I also set up geofences to provide notifications when my wife entered and exited the athlete’s village at the start and also when she got to our predetermined meeting place after the finish of the race. The athlete’s village is the small purple square in the lower left of the image above. Now all that was left was to configure the geofences so that I would be notified via text message.

The images below show the typical notification screens that come up when you finish defining a geofence. You can choose to be notified via email or text message or both. While I have access to both email and text messages on my cell phone, I like to use text messages because there is less time delay between when Garmin sends a message and when it shows up on my phone. Because the geofences were set up to notify upon entrance and exit, both options were chosen. Note that I chose to name the geofence according to the mile splits defined by the geofence boundaries.

Garmin Geofence Notifications

Garmin Geofence Notifications

So with the geofences set up, I put my wife on the bus to the start at 7:30AM and waited for the race to start. Her wave was supposed to start at 10:20AM local time. At 8:30AM I got a message that she had entered the athlete’s village. At 10:02AM she exited athlete’s village. At 10:28AM she was on the course. Below is a sample of these first text messages. Note the 1 hour difference between the time the text was sent and the time reported by Garmin. This is due to time zone settings on my phone, otherwise the time difference between the Garmin time stamp and the message time stamp is almost non existent.

Boston Marathon GTU Notifications

Everything was working well through the first part of the marathon. Because the notifications come from the same sender they displayed one after the other on my phone so I was able to determine her mile splits by looking at the time difference between the notifications. From the data below you can see that she was running a 7:30-8:00 min/mi pace. It was also easy to see which mile marker she had passed. For example, the first notification for the 3 4 5 6 geofence is mile 3, the second is mile 4, the third is mile 5, etc.

Geofence Notifications Mile 3-6

Unfortunately, the closer she got to downtown Boston, the more irregular the messages became. Sometimes they were late. Eventually they stopped coming at all. A quick call to a friend with internet access revealed that the device was inaccessible. The most likely cause for this lack of accessibility was that the cellular network had become overloaded. This not only prevented the Garmin website from sending me notifications, but more importantly prevented the device from sending its location to the Garmin website. Fortunately for me, I was able to get semi-frequent updates on my wife’s status from friends and relatives following her progress on the official Boston Marathon Website.

After the race, I wondered how accurate the information for the Garmin notifications had been. Armed with data from her Garmin Forerunner 305 as well as text and web update data from the Boston Athletic Association I was able to put together the following comparison of splits and paces. You will note that the time of day between the two devices differs by a minute or two. I believe that this is due to a number of factors including inaccuracies in the course drawn on, inaccuracies in the location of my geofences, and also differences in the base clocks of the Garmin Forerunner and the Garmin GTU 10. Most importantly, however, I believe a high percentage of the difference is due to the fact that the GTU 10 only looks for geofence exits and entrances every 30 seconds. Nevertheless, if you compare the mile splits from the FR305 to the mile splits from the geofences you can see that they are pretty close. That is, until the data integrity goes bad around mile 10. After this point, the notifications became irregular and unreliable.

Boston Marathon Splits: Garmin 305 vs GTU

Overall, I am relatively pleased with how the geofences worked. The Achilles heel of the system appears to be the cellular network which became overloaded due to the sheer volume of people using cell phones in the area. My gut tells me that this happens at every big race (Chicago and Boston from first-hand experience), but I firmly believe that using the geofences is a great way to track an athlete during a marathon, especially small and medium sized ones, and will be even more valuable when my wife competes in the Racine Half Ironman and Ironman Wisconsin later this summer.

So to wrap it up, here are my highs and lows for this experience:

1. Be sure to turn the power off and then on again on the tracker after you have set up all the geofences and updated all the notification emails and text numbers. If you don’t, it can take up to 24 hours for the new settings to take effect and the notifications may not go to all of the recipients that you’ve loaded into the web site.

2. Don’t rely solely on this technology to track an athlete, especially if it is a big race where a lot of people will be taxing the cellular networks.

3. Don’t kid yourself into thinking that this technology will give you super accurate splits. At its best, the GTU 10 checks for geofence entry/exit every 30 seconds. This means a split can be off by as much as a minute. It will, however, give you a good idea of when you should start looking for someone at a particular location on the course.

4. Make sure that you set the refresh time for the geofence updates to the fastest setting (30 sec). Also be sure to uncheck the box that allows the tracker to go to sleep when it is inside a geofence.

Modify GTU Sleep Settings

5. Consider having the tracker update directly to your Twitter or Facebook account. This will save you the time of posting to friends and family about how an athlete is doing. I am experimenting with The idea here is that you can get a unique email address where everything you send to that address automatically posts to your twitter account. In effect, this allows the tracker to automatically tweet your geofence notifications. All you have to do is load your unique email address in the Garmin tracking software and the rest is taken care of for you.

6. Make sure you experiment with both text messages and email geofence notifications. One may work better/faster for you.

Thanks for the opportunity to share my experiences regarding the Garmin GTU 10, geofences and the Boston Marathon. The device proved to be a slick way to keep track of my wife’s whereabouts and progress. How’d she do? PR’d by almost 20 minutes………WOOT!

John Breiten is the man in the shadows of his wife Kristy’s budding young triathlon career. When not chasing his four kids, he serves as his wife’s chief bike mechanic, travel agent, technology advisor, chase boat driver and psychologist. You can follow him on Twitter @jdbreiten1.


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  1. far to clever for me…

  2. Great article thanks taking the time to explaining that…

  3. The live tracker option on MapMyRun for iPhone is great. I use to stalk (oops, track!) my wife when she goes for evening walks. Gives me a detailed map of her patch and pace details. It is ace. Sonif you have an iPhone, no need for an extra device! Cheers, Paul

  4. Very detailed, funny and thorough review . . . Boy, kids of the future are going to have trouble being anywhere that they shouldn’t be . . .

  5. hilarious examples of practical uses. Well done, and good guest post.

  6. I was just talking with my husband about how to track me in an upcoming long course tri. I love this idea – thank you for the tutorial! Great guest post! 🙂

  7. thanks for posting this. each fall i do a big endurance (bike) race. it’s a point-to-point race along roads, and i have a support person meeting me at 4 to 6 locations along the way. the problem is they don’t drive the same route that i ride, so they have no way to know if i beat them to a location (which happened last year) and already left, or if i got a flat and they have some more time.

    i can see great use of the gtu 10 for this purpose (assuming they have a mobile device they could use to get the updates).

    one problem, though, is that i pass through some rural areas where cell coverage may be a little spotty, so if this relies on cell network availability i could be out of luck.

    would be nice to give my support crew a 10-minute “heads-up” that i’m approaching the next station. that would save them quite abit of hassle as they wouldn’t have to constantly be “at attention.”

    thanks for sharing.

  8. Ben Wickham

    I’m confused… doesn’t the GTU10 have a live tracker app too? Wouldn’t that save all the hassle of setting up geofences (although admittedly wouldn’t automatically email splits).

  9. Thanks for the post! I’ve been trying to figure out something for IMMOO thie September. Done it several times, but will actually be having spectators this year. Looks like this will work.

  10. Great review! Thanks. And, a great idea you had on getting more notifications for each geofence. What about battery life? If you don’t allow the device to “sleep” then how long is the bat life? Is it a built-in battery or interchangeable? Thx!

  11. Anonymous

    Other options are: Spot satellite tracker. This is good for adventure races because it does not display location data and uses satellites not the cell network.
    I use a boost mobile Motorola (ruggedized) i290 and accutracking. The phone is the cheapest boost phone purchased from ebay and accutracking allows tons of geofences. Instamapper is similar but is free and no support. At a recent IM it worked exactly as desired; the family received text message so they could see me and not have to wait for hours. It also updated my FB page.
    I did find that setting geofences is a bit of an art, because the application had to register a data point inside the geofence to determine entry or exit. So on the bike I had to set the geofences pretty large based on my speed.

  12. Thanks! Now I have idea on how to track my girlfriend so she couldn’t cheat on me. LOLs! Just joking. 😀

    Very useful tips! Keep it up. 😀

  13. Pritom

    Have you ever heard that GPS can be in your belt this is so beautifully soft leather GPS Tracking Belt i just got one and using it no monthly fee needed its worth it