Tips for GPS Improving Accuracy When Running
August 2, 2010 by Bryon Powell · 18 Comments
Through the years, we’ve heard more than our fair share of gripes about accuracy of wrist-mounted GPS devices. We’re not buying most of them. Sure, some of the earliest models, such as the Garmin Forerunner 201/301 were quite finicky, but most models introduced in the last half decade or so are more than capable… if you treat them right. Here are some tips to help you get the most out of your GPS.
First off, make sure the unit has the latest software for both the unit and the GPS chipset. For Garmin products, these are two different updates.
Before setting out on your run, leave the unit in clear view of the sky for 2 or 3 minutes. If you can check the status of the satellite connections, do so before you run. [More for Garmin 205/305 users] Sometimes you can reorient the device to pick up additional satellites that you wouldn’t have acquired had you simply laid out the device. Even though a GPS unit will “acquire satellites” based on four satellites, locking additional satellites improves accuracy and reduces the chances of fully losing your GPS signal under trees or among sky-obscuring terrain.
Check on the GPS satellite status during the course. If possible, pick up new satellite locks en route. Do this especially after passing through forested areas or canyons or when a particular peak has obstructed a large portion of the sky for a while, such as when traversing the side of a steep mountain. You can do this by consistently holding the unit’s antenna toward the sky will moving… or repeating tip 2. The latter is easier and, if you still have some satellite locks, takes less time than before heading out.
If you are able to view a graphic representation of locked and unlocked satellites on your unit, use this screen to help out picking up lost signals by orienting the unit’s satellite toward the direction with the most non-locked satellites (unless there’s a huge obstacle blocking that direction). Be aware that even with a clear “view” of a satellite signal, it can take the better part of an uninterrupted minute to obtain a lock, so be patient.
While it won’t make your GPS more accurate, you can sometimes force a GPS unit to take measurements more often. For instance, a number of Garmin’s wrist top units, such as the popular Forerunner 205 and 305 models, allow you to set the unit on (1) “smart recording,” which varies the measurement rate based on speed, rate of direction change, etc, or (2) to take a measurement every second. Smart recording usually takes a point every couple seconds, while the other option is self-explanatory. Generally, smart recording is plenty accurate and the “every second” option only useful to a race director measuring a course or a similar, but uncommon usage.
If the “every second” method is used, it would be wise to run the data through a smoothing algorithm afterward or slight data variation in GPS points will lead to extra distance. Variation from a unit with great accuracy, say +/- 10 feet, adds up quickly. Note that a unit’s memory fills up much more quickly in “every second” mode, so be sure you need those extra points.
Once you’re back at home, software can further improve your data. For instance, if you upload the data to Garmin Connect, the “Elevation Correction” algorithm does a great job of cleaning up the elevation data. Garmin Connect has automatically applied Elevation Correction to all workouts uploaded on or after April 1. You can manually apply the correction to previously uploaded workouts via selecting “Elevation Correction” under “Additional Information” in individual workouts. This can make a HUGE difference. For example, Elevation Correction reduced an all-day snowshoe outing from 3,991′ of elevation gain to 669′. Those who used Motionbased.com prior to its merger with Garmin Connect might know this feature as “Gravity Correction.”
Call for Comments and Questions
Have you had any frustrations using a GPS during your runs? How about the opposite – has a GPS ever come in particularly handy on the run? Do you have any tips for improving the accuracy of a fitness oriented GPS-unit?
[More info for Garmin Forerunner 205/305 Users
When using your Garmin Forerunner 205/305, you can view your satellite acquisition details by following the below directions.
- Hit the mode button;
- Press down twice and hit enter to select Navigation;
- Press the up arrow once and hit enter to select Satellite;
- You will now see a visual representation of which satellites are or are not locked and where each is located in the visible sky. Locked satellites are a filled oval, while an empty oval is a non-locked satellite. A flashing oval means that the unit has recently received a signal from a satellite, but has not yet acquired a lock. This screen can be useful in aiming the unit to pick up additional satellites.
- Hit either the up or down arrow to see a bar chart of satellite strength. As with the sky view above, a black bar means there's a lock; however, an empty bar means the unit has received a signal, but is not yet locked. A number at the base of the chart with no bar above it means that the particular satellite is in the visible sky, but the unit has not recently received a signal. The top of the chart also shows the unit's current accuracy. If you see tall, but empty bars that don't disappear, keep your unit oriented in the same direction to pick up the satellite(s). However, if you've had you unit on for a minute or more with no bars (or no new bars) visible, move the unit or orient it toward another portion of the sky.]
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Bryon Powell is the Editor-in-Chief of iRunFar.com, which he founded five years ago. Also the author of Relentless Forward Progress: A Guide to Running Ultramarathons and a contributing editor at Trail Runner magazine, he's quickly approaching 10 years as an ultrarunner and 20 years as a trail runner. These days he calls Park City, Utah and its trails home.
All posts by Bryon Powell
I’ve used a variety of Garmin units over the past few years. The biggest gripe I’ve had relates to elevation gain/loss accuracy … or lack thereof. The good news for Garmin Connect users, which I came across a few months ago, is the accuracy seems to be radically improved, if not completely fixed, by enabling ‘Elevation Corrections.’ This feature apparently cross-references your recorded GPS location with survey data and spits out a revised tally. I don’t know all the technical nuts and bolts, but the numbers now seem *much* more accurate (aka way lower). This may be old news, but I thought I’d pass it along anyway just in case.
Stacy,
You’re completely right about the Elevation Corrections feature. I should have included it. The EC feature was in the old Motionbased.com … and then disappeared in the transition to Garmin Connect. I’m glad it’s back!
Bryon,
Good tips, I only have experience with my Garmin 305. It can be pretty finicky once in a while, especially under a canopy of thick foliage. Overall it works great most of the time.
You could do a whole entry on logs that utilize GPS data. It seems like a lot of online logs are now integrated with Garmin devices. I have used the Garmin Connect, Sporttracks (pc based), and attackpoint. I personally think the attackpoint gps integration is done well and the developer of the site is actively adding new “gps” features. At this time it is a premium service ($20 per year I think)
The best GPS is one that is the garbage. Are we mountain runners or dorky tech triathletes??
My word!! jk
Wow! Still seems like a lot of work and living/running in the dense NW forest, this still confirms that I’ll stick with my altimeter/motion based sensor watch. It seems if elevation is the issue, they should make a GPS watch with an altimeter. Just my 2 cents.
I have a Forerunner 405, and I had 2 or 3 drops while running Missouri Mountain on Sunday, and it was in and above steep forested terrain in the bottom of a valley.
The track got screwed up and has a huge straight line jump in the middle.
I had a similar glitch on nearby La Plata Pk that placed me 10k feet underground and under the next ridge over! At the time I was halfway up a huge ridge in plain view, so it must have just been the wrong orientation to the sky.
Anyway, as a result of such failures, I bring a Garmin eTrex as a backup (outside mesh pocket on my pack). It didn’t lose signal on Sunday like the 405 did, so I have one good GPS track.
Good idea about checking the watch when exiting forest, and holding it so it locks again. I may try that next time.
Thanks for the article! I totally disagree with Hone. I like to keep a running log and my Garmin allows me to run wherever I would like to run and still no how far and fast I went. It is also useful when running road races to help with pacing.
Tony,
You are doing the right thing. I would probably be a much better overall runner if I kept track of miles and knew how fast I am running. I am totally unstructured and because of it I am constantly frustrated with my crappy performances. I was just messing around with the comment.
Anyone have experience with the Tech4o pedometer watches?
Yeah, I have the first incarnation – it looks like they may have improved the design a bit since I bought mine, so take the following for what it’s worth. I really liked the watch’s functionality – the few times I used it on a course I’d previously GPS’d, it was acceptably close. However, the buttons were too easily depressed, so my jacket cuff would hit it, or I’d bend my wrist … anything, really, would reset it. It was incredibly (incredibly) aggravating, and I haven’t put it on for well over a year. I just shove my Garmin 60Csx into a pack pocket, or go without. Anyway, to make a long story short — I would categorically not recommend buying that first version to anyone, but it’s possible that they’ve fixed the button problem by now, and if so, it would be a worthwhile purchase. Definitely try it on first, though!
I use the Tech4o Traileader Pro. It is not the most accurate for long distance running or on terrain where your stride length changes. It can basically tell if your are walking or running, then you enter your stride length for each. It does well on shorter runs (less than 10 miles) with consistent terrain. But as your run longer or the terrain is varying from flat to steep or technical you’ll notice that your stride length will vary hence making the distance recorded less accurate. On a short 5 mile rolling trail it usually is over 98% accurate. Everything else works perfect (altimeter, hr monitor, etc) and it is nice not having a footpod. See review: http://www.youtube.com/watch?v=oul7AE5em8k
I’ve enjoyed the distance / speed / heart rate feedback from my Garmin 405 over the last 6 months. Sometimes it goes totally wacky but most of the time it is reasonably accurate, even under tree cover. I agree with others that elevation correction on GarminConnect is a big improvement
I’m wishing that a curious electrical engineering student would hack into the unit and improve accuracy by adding an external antenna (I picture a wire around a headband?)… or a battery booster to improve the stingy 8 hour limit… or an add on that monitors blood sugar or muscle glycogen so I know better when to have another gel or walk instead of run up a hill…
Garmin Engineers, Are you listening!
The battery life is a bummer. My 305 will last 10 – 12 hours at best, but I cannot complain too much as the watch is a few years old and still maintains similar life to when it was new.
I have yet to utilize my 305, this’ll be something else I need to try out soon. Thanks!
Thanks for posting this link on my trail running blog. I will follow your advise to see if I can improve the accuracy of my results. Thanks again!
I don’t use a GPS watch (I use the Garmin FR60 which is HR and pedometer only) but on any run where I wear a Nathan pack, I carry my eTrex Vista (HCX). I don’t worry about elevation, but do get dead on accurate distance measurements which are good for understanding the footpod accuracy (for races where I don’t want to carry the GPS) and the GPS itself on rechargeable AAs gets 36 hours of runtime, so I never really worry about it. I think it’s a great training tool.
All that said, I sometimes do agree with Hone’s joking comment; I’ll take off the GPS, HR monitor, pedometer, tech crap, and just run. Just. Run.