In the early days, runners use the stopwatch feature of their watches to check their Finish Time and it is assumed that the distance of the race route is accurately measured by the event organizers. Today’s generation of runners rely on the GPS functionality of smartphones and watches making it an essential feature. But, how accurate are the GPS of these devices? are they reliable?
I am not an electronics expert or engineer, I don’t know how GPS works technically, so don’t expect me to explain everything with scientific detail. I’m just a runner who relies on my GPS watch and smartphone app to record my performance and this observation and analysis is based on my experience in using them during training runs and running events. I use a Soleus GPS One watch and Samsung S7 Edge for tracking my runs.
Which is more accurate, a GPS watch or a smartphone app?
– Starting both devices and standing still, my S7 Edge using Nike Run Club app connects faster to GPS satellites than my GPS One. It usually takes less than a minute for the S7 to get a good signal, whilst the GPS One can take as long as 1-3 minutes to find a signal. The GPS One may also receive an unstable connection and deliver very unbelievable results like a running speed of 40-70 kilometers per hour which is impossible considering that Usain Bolt can run at a top speed of 44 km/h. The GPS One also has a tendency to lose signal in places where only a few tall buildings surround the area. There are times that the GPS One can yield better results than the smartphone like the time I ran the 2nd Philippine Marine Corp Marathon. When I entered the famous Kaybiang Tunnel, both devices lost connection, but the watch re-connected faster and delivered a more accurate distance. It should be noted that I was using a mid-range smartphone at the time, an Alcatel Flash 2, and not the S7 Edge that I’m using now. I mentioned this because high-end smartphones and GPS watches with superior hardware may be able to deliver more accurate results than entry-level like the GPS One and mid-range devices.
UPDATE (07-23-2017): I accidentally activated the mobile data of my S7 Edge instead of the GPS. Nike Run Club app relied on internet connection and due to the weak signal and speed, it resulted to a big miscalculation, counting 600-800 meters as 1 kilometer.
– Distance discrepancy between the two devices is not unusual. Sometimes it can be as short as 100 meters to as long as 2 kilometers with the GPS watch very likely to be inaccurate. One example of this was during Run United Exceed half-marathon last April, GPS One recorded the total distance of 23.45 kilometers, whilst the S7 showed 22.5 kilometers. The race route in Bonifacio Global City is surrounded by tall buildings and locking on to the satellites takes time, but I was able to get a signal for both devices before the gunstart. But, I’m very sure that the GPS One was inaccurate because it showed me that I passed the first kilometer in 4+ minutes whilst the smartphone app told me that I ran it at 5 minutes and 45 seconds. I’ve also seen social media posts from runners and most of them also covered 22+ kilometers. Others got results of less than 21 kilometers, but it’s very likely that they started their devices while it was still trying to get a signal and only got one after several kilometers (i.e. 18 kilometers of total distance was likely the result the device receiving a signal after 3 kilometers of running). During my usual Wednesday and Friday morning runs, it’s often that I get distance discrepancies and most of the time, the GPS One delivered inaccuracy.
GPS devices or just trust the Organizer’s Race Route?
– What you see in your GPS devices can also match the race course distance if you get a very good signal. But, the race route can be more or less of the total distance as advertised. It depends on how the organizer of the event measured the race route and there are some instances that could force the organizer to shorten distance like unfavorable weather or last minute changes due to traffic and other road-related incidents that is beyond their control. Other organizers will add extra kilometers as a bonus or a slight change in the race route. If you really want a distance accurate race route, then look for an event sanctioned by an athletics organization like Philippine Athletics Track And Field Association (PATAFA).
Comparison with Car Odometer (FINAL UPDATE)
I did an experiment to compare if the distance displayed on a car’s odometer will yield the same or close results with the GPS devices. I did a quick google search and found out that GPS is much more accurate than car speedometers when it comes to measuring speed because it is affected by tire size and condition. But, I’m measuring the distance and disregarded speed, so we focus on the odometer. Stopping the car at 1, 3, and 5 kilometers, the distance difference is somewhere between 30 to 200+ meters.
This experiment should be taken with a grain of salt since gps reading is affected by the position and availability of the satellites (take note that the experiment took place on a road devoid of tall buildings). It’s likely that distance discrepancy will increase if I travelled farther.
The verdict: Accurate or Fu*k-urate?
– So, are GPS devices like smartphones and GPS watches accurate when it comes to measuring distance and pace? the answer is yes… but, only if you get a good and stable signal. The advance technology in these devices assures you accuracy, but not always. There will be times that you will get unstable signal and even lose the signal especially in places surrounded by tall building or trees and that guarantees fu*ked up results. The reason why I use both a GPS watch and smartphone app is for cases when one fails, the other won’t (hopefully). A small distance discrepancy (like 100-300 meters) between both devices is acceptable, 500 meters or more is where you start to question accuracy and pick the one with less distance. In my usual training routes, I can tell which one is giving me the likely accurate distance because of the numerous times I ran on that place. Even if that devices failed to connect with the satellites, I remember where the kilometer points are.