Suunto 9 with the recent GPS firmware was among least accurate GPS watches in today's 25K trail race

Dimitrios Kanellopoulos

That is not correct. The production of gps points is not per se based on distance nor does the distance increase every 10meters. It depends on the quality of the Gnss

nseslija

@sky-runner SV welcome back to Suunto forum

sky-runner

@Dimitrios-Kanellopoulos May be you are right, but that is my observation from looking at multiple FIT files. Distance between points was pretty much always greater than 10 meters and the time between points was usually 3-4 seconds when running on trails, sometimes longer.

Łukasz Szmigiel · S9PP 2.40.44

@sky-runner I’ve noticed there’s quality threshold in Suunto watches - watch won’t save a point if quality is below certain threshold. This way the path recorded is more sane in difficult conditions (less wobbly) but it may be refreshed less often.

zvonejan

@Łukasz-Szmigiel

hmm interesting. I have no complains about accurancy on suunto devices, but distance between ponts are between 3-15 meters.

suunto

but on garmin distance between points are consistent and much shorter

sartoric

Maybe (and maybe it was already explained) it’s a way to optimize “disk” space.
You don’t need to save N points for a straight line, 2 are enough, even if the watch is reading info every second.

sky-runner

@Dimitrios-Kanellopoulos

Here is an example from a race that I did with Suunto 9 back in January. I used an online tool to export FIT file to CSV, then added a column which is a distance delta from the previous distance, then created a graph with timestamp on X axis and distance delta on Y axis. Perhaps that isn’t the best possible analysis, but something I could do very quickly. You can see a very distinct cutoff at 10 meters for the most of the activity. There were just a few points with 6-9 meters between the points.
It is interesting that it dropped to 3 meters between the points at the end, but that is where my watch had issues with GPS and it wasn’t getting GPS signal for most of the time.

Screen Shot 2020-09-05 at 12.14.15 PM.png

The overall duration of this was about 2 hours. The terrain was fairly flat but nearly 100% of it was under tree cover.

sky-runner

Here is a similar graph from another run. Yes, occasionally the distance between the points is less than 10 meters, but for the most part it is 10 meters or greater - there is a clear threshold visible on the graph:

Screen Shot 2020-09-05 at 12.49.25 PM.png

ollemelin

Alright then. I’ve done some more tests with SB9 and my conclusion is that SB9 measures about 20-30 meters short on every km compared to Maps, Garmin devices and various apps like strava. Strava, garmin are spot on with maps most of the time.

I’ve tried different kinds of GNSS-combos on SB9 but with same results.

What do you think? Sameting wrong with my device? Some days ago i ran with a friend with Spartan baro and my SB9 came short also with him.

cosme.costa

@ollemelin said in Suunto 9 with the recent GPS firmware was among least accurate GPS watches in today's 25K trail race:

Alright then. I’ve done some more tests with SB9 and my conclusion is that SB9 measures about 20-30 meters short on every km compared to Maps, Garmin devices and various apps like strava. Strava, garmin are spot on with maps most of the time.

I’ve tried different kinds of GNSS-combos on SB9 but with same results.

What do you think? Sameting wrong with my device? Some days ago i ran with a friend with Spartan baro and my SB9 came short also with him.

I usualy run with a friend that uses an Ambit 3 Run and my S9B is always short on distance. I think that is something that Suunto knows (from what I recall in others posts). For me is not a big issue, I can live with that. What I’m not so sure is that Garmins are spot on, I guess it depends on the model. If I see the tracks of some people using Garmin (mainly Fenix) they are OK but not spot on, and if the track is not ok can’t be the distance 8Except if they do corrections when uploading the the activity to their servers). And when you say Strava is spot on, what do you mean? planning a route or recording it with a phone?

ollemelin

@cosmecosta

I just don’t really get the reason why it is this way. I like suunto and the new app is really great, but this measurement issu is really bugging me

Thinking about buying an stryd-pod…

Dimitrios Kanellopoulos

20-30 per km = 200-300m per 10km = 800-1200m per 40 km to put it in perspective.

@ollemelin are those results from trails ? Or road ? How would you categorize the “conditions/visibility” of GPS.

Owning a stryd in general terms will make you stop thinking of any GPS based watche’s accuracy. However by far I dont say that like: Buy stryd. It’s just because it will give you the correct, consistent cross watch results. You will stop worrying about a bad GPS day etc etc. Get an older version of 100e Your Suunto, Garmin, Polar, COROS will love it

ollemelin

@Dimitrios-Kanellopoulos

It’s not a GPS visibility problem. The measurement is consistent on track, road and trail. In surveying we call it ”systematic error” and the device needs calibration.

Ofc the error seems small long distance but its really bad for shorter distances. It’s bad when apps like strava or runkeeper makes a better job.

Does it matter for my running development? No! But i still wish Suunto to fix this issue

Dimitrios Kanellopoulos

@ollemelin I dont argue. By far. From what you said the error is huge for long distances.

But you didn’t reply on the conditions of the “systematic” error.

ollemelin

@Dimitrios-Kanellopoulos

Sorry! I misread your answer.

Yesterday i ran in perfect conditions. Clear blue sky. Straight road and no trees. 20-30 meters short compared to map, garmin 735 and strava.

But I also run trails with trees etc and about same drift Every time

Dimitrios Kanellopoulos

@ollemelin Roger that.

Let’s see what a new gps firmware can bring.

In theory and according to our tests and fieldtesters the distance on simple paths is ok. On some cases of trails it can be short. According to recent researches and academic papers this doesn’t vary so much as you you say but I don’t argue. I have seen this feedback personally many times.

I can only ask you to “wait” I don’t have anything else to propose atm unfortunately.

However it would be super interesting even if you , your friends etc tested stryd on the same route / run.

Have a great weekend, I am signing off at least for today

ollemelin

@Dimitrios-Kanellopoulos

Thanks. I have some extra money to spend so I think I will buy an stryd. Maybe i can test in my work aswell

Łukasz Szmigiel · S9PP 2.40.44

@Dimitrios-Kanellopoulos just out of curiosity - is there anything being done to those strange offsets that occur in first 10 - 15 minutes of workout, especially if one starts the workout fast (without giving the watch some time after the GPS arrow is green) and / or in demanding gps conditions?

Such offsets do autocorrect after some time and change of direction (ie. 90 deg) but this behavior is strange. Is it because fusedspeed has priority if signal is below certain threshold?

Dimitrios Kanellopoulos

@Łukasz-Szmigiel I didn’t know about what you just said but yeah it sounds possible because I can think about a reason behind it, that actually has many times caused a headache.

When the “GNSS lock” / “SOLID Green arrow” happens it means that the signal is quite good for you to go on. It aint perfect. Depending on the environment it will vary.

Now consider that a quick start (for running mainly) means arm movement, a lots that is, and a “good” GNSS lock.

I think we can all agree it can drop the “signal strength”/“lock quality” quite easily, as in contrast to cycling with little arm movement. Why would it then?

Here is an extra case: Hard conditions (eg canyon) to get a lock, and after a weak lock, you go run in the forest in the canyon. … You might loose GPS.

I hope it makes a little sense. What I wrote above applies to all brands, and is less/more effective depending on the antenna position. I hope it helps

Łukasz Szmigiel · S9PP 2.40.44

@Dimitrios-Kanellopoulos thanks for explanation. I was suspecting fusedspeed and the way firmware interprets GNSS signals to avoid zigzagging between readings.

Here’s a run from today, fresh, for reference. I’ve started running right after obtaining GNSS lock (GPS + Beidou) but pressed start after ~50 meters. Conditions were meh at best - it was raining all day and it’s still overcast. QS link.

I’ve marked actual path in pink:

Here you can see start and finish (~35 minutes later). Start is offset while finishing path is spot on, I’d say up to 3 meters.
Continued from last screenshot.
And right before I’ve entered the park when it auto corrected after a short path on embankment. This is interesting as I’ve entered a wooded area but nevertheless the accuracy improved and the offset was gone from that moment.

Just to be clear - I’m not complaining, I just find this behavior fascinating and I’d like to dig deeper into it and perhaps know how to reduce it when accuracy may be more important than on a regular “everyday run”.