# Ambit speed accuracy



## rkendall (Apr 1, 2012)

I'm a little concerned with the speed accuracy of the Ambit, here is a 5 mile walk I did today around the neighborhood walking I like at a relatively consistent speed yet when I look at the speed realtime during the walk I see huge fluctuations between 0 mi./h in 5 to 7 mi./h. I have good visibility of the sky so I would expect my pace to be about 3.2 - 3.6mph. if you look at the download the data you see that the speed is jumping up and down significantly, I'm not sure other GPS of watches smooth this average but the real time speed is useless at walking speeds for me. Is anyone else seeing this? I'm on firmware 1.07ThanksRobert


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## cobrapa (Mar 15, 2012)

Hmm, that's pretty interesting. What profile did you use? Was it one of the defaults or your own setup?


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## buzz819 (Sep 18, 2010)

Was fusedspeed turned on?

I am yet to try out my GPS on the watch, so am interested to see if works well,

Buzz


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## bjw29 (Jan 3, 2012)

I actually used the GPS driving from Tn to Va a couple of days ago and it seemed to be almost accurate with what my speed was.


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## rkendall (Apr 1, 2012)

It was the default walking profile. And this is a multi mile non stop walk (i.e no cross walks to anything to throw off the speed) while I was walking I would glance down and see the speed be 5.1 mph then change to 2.1 then bounce to 3 all in the matter of seconds with no change in my real speed.


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## rkendall (Apr 1, 2012)

I think at high speed errors smooth out, walking at slow speeds is a different beast I would assume. But its a good thought I will test in the car tomorrow and compare to the speedometer.


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## cobrapa (Mar 15, 2012)

One of the things I've been wondering about is what kinds of things would throw off FusedSpeed. The manual mentions that holding the watch out to look at it will reduce speed accuracy (or something of similar wording.) I suspect that they map arm swing detected by the accelerometer to gps speed. That makes me think that stopping swinging your arm in whatever natural rhythm you have may mess with speed readings. I haven't done any testing to prove that though.



rkendall said:


> It was the default walking profile. And this is a multi mile non stop walk (i.e no cross walks to anything to throw off the speed) while I was walking I would glance down and see the speed be 5.1 mph then change to 2.1 then bounce to 3 all in the matter of seconds with no change in my real speed.


I don't see a walking profile on mine. Do you know what sampling and storage rates are setup on that profile? Maybe it was 'Trekking'? That profile is 60s gps and 10s everything else. That seems pretty infrequent for good speed. Although I'd think they would average over the long time spans. Sounds like some kind of bug to me.


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## cobrapa (Mar 15, 2012)

Here's a run/walk I did. Only ~8min, with the slower speeds walking. But the run profile has higher sampling rate. There is a section near the end with odd speed jumps as well. But overall seems pretty reasonable.


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## rkendall (Apr 1, 2012)

Its a profile from the drop down list, I configured all the settings to 1 sec accuracy.


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## rkendall (Apr 1, 2012)

Now yours looks perfect I don't see any of the drop to zero's in yours that I see in mine. Yours looks like a altitude curve which is what i would expect for normal walking. What profile did you use for that?


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## cobrapa (Mar 15, 2012)

That's with the running profile. Yours does look odd, I'm not sure what's going on there.


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## Mystro (Oct 26, 2008)

I did a log on my garden tractor spreading weed and feed. It's speed was accurate with a top speed of 2.8 mph. I was going very slow with starts and stops and everything in the sumerary looks accurate. I did another small walk log and there wasnt any spikes but i wasnt swinging my arms as if i was running. There might be somthing to the swinging the arm thing.


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## rkendall (Apr 1, 2012)

Partly I think it might be the scale when I zoom into a 8 min segment it looks better but still very random.









Now when I look at a cycling chart it seems a little less random. (I actually believe the cycling speed fluctuation)


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## paduncan (Sep 28, 2007)

That doesn't look good to me at all. The speed profile should be much smoother.

Here is what a walk / run looks like on the Garmin FR 610 (the large spike is where I stopped to adjust something).


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## buzz819 (Sep 18, 2010)

I just went for a quick run, it looks pretty good to me,

here it is;









I thought it looked quite good, maybe over a longer distance it would show more peaks and troughs, as they would be squeezed up tighter??

Buzz


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## pjc3 (Mar 26, 2012)

> FusedSpeedTM is activated automatically with the following exercise modes:
> 
> ● trail running
> 
> ...


Fusedspeed not active in many modes


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## rkendall (Apr 1, 2012)

pjc3 said:


> Fusedspeed not active in many modes


Whats intersting is I just noticed in moves count you can tell what is using fusedspeed in the lower right. Oddly the default profile walking don't use it.


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## cobrapa (Mar 15, 2012)

Yeah, that's what made me ask which profile you used and what the settings where. I'm haven't seen a lot of data yet about how well FusedSpeed works or doesn't work.


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## rkendall (Apr 1, 2012)

Okay here is more data, I went out for a 5.8 ish mile walk with the Ambit on one hand and a Garmin 910xt on the other. Now at the end they agreed on most things the Ambit said I did 5.83 miles and the Garmin said I did 5.86 close enough. They even agreed on on altitude the Garmin was not at the correct starting elevation but the trend and overall difference was negligible. This time I confirmed i was using a fusedspeed profile, and what I noticed and you can see in the data below seems to show that the Garmin is averaging things out over a a few seconds to remove the excessive speed osculations. For example you can see in the Ambit thought I was bouncing up to 5 or 6 mph where the Garmin shows a more more likely effect that I was hovering about 2.8-3.2 most of the time. I don't think there's a defect in the watch otherwise the overall distances would not be so spot on, but it appears that the Ambit is not smoothing the data which is making the real time feedback on speed useless for me. Now I also took the ambit for a drive and at speed over 7mph the speed was dead on so it seems to be a problem at slow speed activities. If anyone has a contact at Suunto I can happy give them the detailed logs.


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## cobrapa (Mar 15, 2012)

Those spikes seem odd. Suunto has a trouble/question report option on their website if you want to send them a report (or maybe someone here has more direct access.) I'll try some walking data myself and see what I get. I wouldn't expect those spikes. Maybe you got a bad accelerometer in your unit.


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## XCJagge (Mar 1, 2012)

My speed graph looks usually like this (part of the 20k run I did yesterday):







I stopped once and pace dropped to zero.


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## XCJagge (Mar 1, 2012)

I did an little experiment today. I ran with three devices, Ambit, t6c + food pod mini (calibrated for other shoes) and Globalsat bt-335 gps (über accurate gps logger,my precious). here is speed graphs:

Ambit:








T6c+ foot pod:








Globalsat logger:








Part of track logged by the Ambit:








In fourth "sprint" I tried to run three different paces, Ambit recorded those pretty well. At halfway I stopped for four seconds and on my way back one for two. I ran under a the bridge seen in the map image twice, can be seen as spikes in Globalsat's graph. Also, pace changes are more instant in Ambit's less averaged graph compared to Globalsat's graph. I can't say why Ambit's speed graph is exceptionally flat in places here, but I am happy with it. Maybe because I tried to keep steady pace and tried not to look at the watch at all.


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## rkendall (Apr 1, 2012)

Your speeds are pretty decent, what happens if you take a walk at 2-3mph for a few mins? I'm wondering if there is a low speed at which it wigges out. Or if mine is just defective : ) Are you record rates for all settings 1s?


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## Jeff_C (Feb 11, 2006)

FARTLEK!

I still giggle when I say that... sorry.


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## scandium21 (Nov 28, 2007)

Interesting - can I ask what the difference was for Pace and Mileage info between the T6c with footpod mini and the Ambit??



XCJagge said:


> I did an little experiment today. I ran with three devices, Ambit, t6c + food pod mini (calibrated for other shoes) and Globalsat bt-335 gps (über accurate gps logger,my precious). here is speed graphs:
> 
> Ambit:
> View attachment 669188
> ...


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## or_watching (Nov 13, 2008)

XCJagge,
In your three-device experiment, where the Ambit shows a very flat pace, do you know for certain if this is the FusedSpeed value or the GPS-only value?
I forget, are both are logged in the xml file?

In either case, that's pretty remarkable precision if your pace was really that steady and the watch captured it so. (Suunto's whole intent of the FusedSpeed innovation)
-----
(in case both are not logged in the Ambit xml file...) if there are any super-enthusiast nutters out their with TWO Ambits who want to show us a graph with Fused-speed on and off for the *same* run, that'd be a really fun comparison showing the effect of this landmark feature.
---
I'm also interested in walking/hiking pace and track data. It's an important test of the implementation of the GPS algorithms - several watches out there have had major hiccups at low speed that needed subsequent firmware updates. (Like they had only validated the watch at running pace).


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## or_watching (Nov 13, 2008)

Jeff_C said:


> FARTLEK!
> I still giggle when I say that... sorry.


And if you are traveling to Scandinavia, don't forget to have your fartplan printed out. But nowadays I believe there are also Fartplan Apps.
_(normally I'm mature, but when the moderator starts something...)_


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## Mystro (Oct 26, 2008)

Tested the speed accuracy in a car with two other gps units. The Ambit was dead accurate with the others, even to the tenths of a mph. The Garmin Nuvi would read 67.4 mph and the Ambit would read 67.3 mph.


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## rkendall (Apr 1, 2012)

At speeds over 5mph mine tracks perfectly also, we need a few people to do a slow leisurely walk <3.5 mph and see what happens : )


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## Jeff_C (Feb 11, 2006)

Sorry... sorry... Step away from the computer...


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## martowl (Dec 31, 2010)

rkendall said:


> I'm a little concerned with the speed accuracy of the Ambit, here is a 5 mile walk I did today around the neighborhood walking I like at a relatively consistent speed yet when I look at the speed realtime during the walk I see huge fluctuations between 0 mi./h in 5 to 7 mi./h. I have good visibility of the sky so I would expect my pace to be about 3.2 - 3.6mph. if you look at the download the data you see that the speed is jumping up and down significantly, I'm not sure other GPS of watches smooth this average but the real time speed is useless at walking speeds for me. Is anyone else seeing this? I'm on firmware 1.07ThanksRobert


I have not seen your issues. I do know that if you stop to look at the watch and interrupt the arm swing or if you do not swing your arms, the accelerometer will not work properly. Here is a run I did after a long hard run the day before. I walked up the steep sections early in my run, this is on a narrow steep trail so my speed was not constant. I think the Ambit did a very good job, you can see where my speed becomes more consistent running downhill on a wider, flatter trail in the middle of the run. I am not seeing the same problems you are.


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## cobrapa (Mar 15, 2012)

Here's a short walk I did today, made sure to do some slow sections. Also did arm swing and hands in pockets a bit. It doesn't seem to jump around as much as your data, do you think? What kind of sky coverage for the gps view do you have for your data?

For those who have heard of Valley Forge National Park, you might recognize this little map section. ;-)

















Recording interval 1s, gps recording 1s as well, using the Running profile. I looked at the logged data a little. I'm not sure how to tell if it reports FusedSpeed or not without a bunch of math. The gps data doesn't have speed, just Lat/Lon per point, but the non-gps data does display a speed number. I'm guessing you could get FusedSpeed from it and gps speed from position calculations.


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## rkendall (Apr 1, 2012)

Out of curiosity was the recording rate 1 second or 10 seconds?


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## cobrapa (Mar 15, 2012)

Both one second, post updated.


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## rkendall (Apr 1, 2012)

What are you using to look at the raw data?


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## XCJagge (Mar 1, 2012)

scandium21 said:


> Interesting - can I ask what the difference was for Pace and Mileage info between the T6c with footpod mini and the Ambit??


Ambit 4.99 km
Globalsat 4.98 km
T6C with uncalibrated foot pod: 4.32 km
Correct distance is about 5 km.

There is no gps speed data in xml file. But where speed is entirely flat there is some little pace changes in xml, smoothed or too small to be seen in movescount graph I guess.


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## cobrapa (Mar 15, 2012)

I was just looking manually at the xml file data points to see if there where more than one speed number reported per sample point. I assume they don't tweak that Lat,Lon points based on accelerometer data, so I'd guess the non-gps speed reported point might show a difference based on it.


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## theotherphil (Nov 2, 2009)

Running profile selected but a short walk along the beach. Maybe not the best surface to be walking on for consistency but the graph shown seems pretty accurate. I stopped for a short period for a chat mid walk and towards the end slowed down to climb some steps.


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## rkendall (Apr 1, 2012)

You don't find it unreasonable that within a single second that you have a 1-3 km/h change in speed?


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## cobrapa (Mar 15, 2012)

That's interesting. His data has the spikes you saw. I don't think it's reasonable. :think:


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## rkendall (Apr 1, 2012)

Here is a update, I reset movescount and even the gps on the watch from the service menu just to make sure its not something I did. Then I did a out and back walk on the same path the first half in trail running mode so that FusedSpeed was used. The second on the way back i did cycle mode so fused speed would not be used. You can see on the same path that the cycling was very stable at my walking speed. In fact the the only spikes you are see is when I was swinging my arm walking normally (which was odd because FusedSpeed was suppose to be off so) but most of the time I had the tips of my hands in my sweatshirt (the ambit was outside facing the sky) but its very obvious that the FusedSpeed is where the errors are coming from. So its possible I have a bad accelerometer.


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## pjc3 (Mar 26, 2012)

Fusedspeed is only active in a selection of sports which are running based.........this is probably for a reason. The algorithm may well need a certain threshold of accelerometer input before it can use it effectively for data smoothing. Walking may not produce that accelerometer input.


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## rkendall (Apr 1, 2012)

While I agree with that, as you can see in the cycling chart, even with FusedSpeed off just a normal arm movement makes the data unusable. I don't think Suunto is doing different logic based on sports profile outside of FusedSpeed on or off, so walking with any arm movement should not cause the huge spikes we are seeing something is wrong with there smoothing algorithm that it is too accurate i.e. it is measuring the velocity of the arm moment at points in time which is much faster or slower than the pace over a few second period.


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## theotherphil (Nov 2, 2009)

rkendall said:


> You don't find it unreasonable that within a single second that you have a 1-3 km/h change in speed?


Like I say, walking on a sandy beach probably isn't the best surface for testing the accuracy of me moving at a consistent pace....especially walking with my gf. I'll do another test later on a more suitable surface with no distractions lol


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## black_fx_35 (Mar 28, 2012)

theotherphil said:


> Like I say, walking on a sandy beach probably isn't the best surface for testing the accuracy of me moving at a consistent pace....especially walking with my gf. I'll do another test later on a more suitable surface with no distractions lol


Ummmm, leave the Ambit at home as it is the distraction. Take the girlfriend....

Just saying...


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## theotherphil (Nov 2, 2009)

Look, I really think that this is a non issue and here's why. GPS has a best case scenario of 1 meter accuracy. In order to provide a smooth graph, to overcome this 1 meter (in)accuracy you need to be moving _at least_ 1 metre per second. That's 3.6kph or 2.23mph as a minimum. By selecting a 1 sec recording interval at walking pace, you will be picking up this inherent fluctuation in position of up to 1M in best case scenario (using a running profile for example). This is a limitation of _all GPS_ not just Suunto. In some cases, you will see the graph fluctuate by it's level of accuracy at slow speeds or even standing still (spikes of 3.6kph or 2.23mph). Fusedspeed is only going to compound this problem at these paces.

My advice is to use a profile with a longer GPS fix interval - 5-10 secs would be ideal but not yet an option in the movescount site. It is interesting to note that the trekking profile uses 60s fixes....which is more than adequate at walking pace.


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## theotherphil (Nov 2, 2009)

rkendall said:


> While I agree with that, as you can see in the cycling chart, even with FusedSpeed off just a normal arm movement makes the data unusable. I don't think Suunto is doing different logic based on sports profile outside of FusedSpeed on or off, so walking with any arm movement should not cause the huge spikes we are seeing something is wrong with there smoothing algorithm that it is too accurate i.e. it is measuring the velocity of the arm moment at points in time which is much faster or slower than the pace over a few second period.


As stated in my previous post, what you are seeing is the inherent inaccuracy of 1 meter resolution at slow speeds and 1s GPS fixes. In your cycling example, fused speed is off but you are still travelling close to the minimum speed of 3.6kph in order to provide reliable speed data and this is where you will encounter spikes in the graph. With a 1s GPS fix, even stood still you can potentially see spikes in speed. Using the running profile with fusedspeed on, it will compound the problem.

Ideally, a 5-10s GPS sample rate could be used but until that is an option on movescount, using the trekking profile with 60s sample rate will fix this "problem".

There is nothing wrong with your Watch and the accelerometer is working fine.


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## rkendall (Apr 1, 2012)

I agree, as you can see from the earlier post thought the Garmin 910xt on the same course had none of these issues because I think its averaging the sample over several seconds. Hopefully this will be fixed sooner than the fall update because this is a watch marketed to hikers and 3 MPH up a mountain is not a super slow pace. IMHO


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## rkendall (Apr 1, 2012)

I should also add i also have a Polar RCX5 with a G5 GPS and it does not have any issues at these speeds. So Garmin is okay Polar is okay, Suunto is not. Considering its the highest priced by far of the three (and I honestly think by far the best in theory) I hope this can be fixed.


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## theotherphil (Nov 2, 2009)

rkendall said:


> I agree, as you can see from the earlier post thought the Garmin 910xt on the same course had none of these issues because I think its averaging the sample over several seconds. Hopefully this will be fixed sooner than the fall update because this is a watch marketed to hikers and 3 MPH up a mountain is not a super slow pace. IMHO


That's right but the trekking profile eliminates this problem. Even with a 60s sample rate, you'd have to be walking pretty fast to go further than 100m...the accuracy difference of your track log will hardly be noticeable using 60s sample rate vs 1s, but you get much better battery life and longer recording. When walking/ trekking, it is not that important to know your current speed by the second....instead, distance travelled, time travelled and average speed is more important.


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## theotherphil (Nov 2, 2009)

rkendall said:


> I should also add i also have a Polar RCX5 with a G5 GPS and it does not have any issues at these speeds. So Garmin is okay Polar is okay, Suunto is not. Considering its the highest priced by far of the three (and I honestly think by far the best in theory) I hope this can be fixed.


_All_ GPS devices will have this problem when using a 1s sample rate and slow speeds. It is an inherent accuracy problem of the GPS system as a whole, not an individual device.


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## cobrapa (Mar 15, 2012)

I think you have a misunderstanding of the accuracy of gps. Where do you get your 1m ideas? gps, especially position accuracy in a local area without some sort of signal problem can have very good positional accuracy (meaning, if I take a position, then try to find that position again with the same equipment, in the same general physical location) in the range of less than an inch (under a few cm for you metric folks.) This is the basis for US based WAAS correction and for differential gps used by surveyors and the construction folks.

Now, it's entirely possible that there are factors that make you not able to resolve a position to less than 1m. But for walking, in close proximity to the last reading, these are not to be expected. Unless you both live in electrically hostile environments, or have some unusual overhead cover that distorts the frequency of gps satellites.

All I'm saying... I don't buy your 1m argument.  No offense intended.

Here's a silly thought. Which side of your wrist do you two guys wear the Ambit on? Facing out or facing in? I don't think it should matter, given what I've seen of the Ambit's reception, but it doesn't give much indication of poor gps reception, so I'm not sure we can tell when it has poor position reception.


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## rkendall (Apr 1, 2012)

I agree, and we are not just talking about raw input coming from a gps signal We count on the software in the watch to do the right things, consider the other two watches can handle this scenario means its not a impossible one. I personally wear mine on the left hand which means the gps module is facing towards me


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## cobrapa (Mar 15, 2012)

On the left, but antenna above your wrist or below?

Here's a detailed discussion, but doesn't answer our question.

Error analysis for the Global Positioning System - Wikipedia, the free encyclopedia

Note that it says civilian accuracy is about 5m (16ft), but this is for an absolute position fix. This is not the reading to reading accuracy that speed calculation depends on.


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## rkendall (Apr 1, 2012)

Here is a picture


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## cobrapa (Mar 15, 2012)

Same way I was wearing mine for the data I took. Rules out antenna facing down problems.


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## theotherphil (Nov 2, 2009)

cobrapa said:


> All I'm saying... I don't buy your 1m argument.  No offense intended.


Non taken! Have a look at Page 84, Suunto Ambit user guide:



> GPS technology: SiRF star, resolution: 1 m/3 ft


As for my understanding of the technology....many years as a Forward Observer, 29Cdo Reg, Royal Artillery.


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## theotherphil (Nov 2, 2009)

cobrapa said:


> Note that it says civilian accuracy is about 5m (16ft), but this is for an absolute position fix. This is not the reading to reading accuracy that speed calculation depends on.


That is using an uncorrected signal. In the US, WAAS signal correction is available and in Europe EGNOS. This can give up to 1M resolution.


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## cobrapa (Mar 15, 2012)

But you understand the limits of WAAS then? Is EGNOS limited as well? In the USA, WAAS is provided by low horizon satellites, which makes it only helpful in very flat areas or above ground level (for aircraft use.) I wonder if the Ambit has WAAS/EGNOS enabled.

The 1m spec is still an absolute accuracy spec though. Do you agree? 1s measurements will have a much higher accuracy in relation to each other. Are you suggesting that reading to reading at 1s intervals could vary up to 1m? I don't think that is the case.


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## theotherphil (Nov 2, 2009)

cobrapa said:


> But you understand the limits of WAAS then? Is EGNOS limited as well? In the USA, WAAS is provided by low horizon satellites, which makes it only helpful in very flat areas or above ground level (for aircraft use.) I wonder if the Ambit has WAAS/EGNOS enabled.
> 
> The 1m spec is still an absolute accuracy spec though. Do you agree? 1s measurements will have a much higher accuracy in relation to each other. Are you suggesting that reading to reading at 1s intervals could vary up to 1m? I don't think that is the case.


WAAS/EGNOS correction is usually provided by ground based transmitters. The absolute accuracy is going to be 1m resolution given no outside interference etc. 1s measurements won't give better accuracy - just more sampled points. Accuracy around a given point is still only 1m. Many GPS units attempt to combat this this slight variation around a point at slow speeds by assuming the unit is stationary therefore will not update it's current position at slow speeds. Google "Garmin low speed accuracy" - there's many problems reported. The reason is, the software assumes that the unit is stationary at slow speeds and discards the readings as drift related to the 1m resolution. In some cases, you can walk at very slow pace for 50+ meters and the software in the unit discards this info as drift in the signal.

Here's an example:





Imagine a circle of 1m with you stood on the perimeter. Imagine jumping from edge to edge of that circle every second....that is what the software can pick up as movement and with a 1s sampling rate, can show speed spikes of 1m/s (3.6kph).


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## pjc3 (Mar 26, 2012)

Same circuit, 3 different modes walking briskly. Some dense tree cover, some clear.

Recording interval 1sec, GPS recording rate 1sec No Fusedspeed









Recording interval 10sec, GPS recording rate 1sec Fusedspeed active









Recording interval 1sec, GPS recording rate 1 sec Fusedspeed active


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## cobrapa (Mar 15, 2012)

theotherphil said:


> WAAS/EGNOS correction is usually provided by ground based transmitters.


I'm not familiar with EGNOS, but this isn't quite how WAAS works in the USA... (Or maybe you're just simplifying it a lot?) All I was try to say is that for hand held units like Ambit & Garmin, the WAAS signal comes from WAAS satellites which are 10deg off the horizon ( geosynchronous orbit .) In the USA, it can be hard to receive the WAAS correction data if your view of the southern horizon is limited, which limits use of the correction data. The handheld units I've looked at, as well as the Ambit, receive the signal from satellites, not directly from ground based stations. Is EGNOS different?



> ...
> 
> Here's an example:
> Sticky problem - Garmin eTrex 30 vs. Garmin GPSmap 60CSx - YouTube
> ...


Hmm, I've not looked in to this. The video makes it look like a problem with some Garmin units though, not a general 1m behavior with gps. (In my opinion)



pjc3 said:


> Same circuit, 3 different modes walking briskly. Some dense tree cover, some clear.
> 
> Recording interval 1sec, GPS recording rate 1sec No Fusedspeed


Your first graph is interesting... Where you walking a consistent speed? That speed graph varies quite a bit!


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## theotherphil (Nov 2, 2009)

cobrapa said:


> I'm not familiar with EGNOS, but this isn't quite how WAAS works in the USA... (Or maybe you're just simplifying it a lot?) All I was try to say is that for hand held units like Ambit & Garmin, the WAAS signal comes from WAAS satellites which are 10deg off the horizon ( geosynchronous orbit .) In the USA, it can be hard to receive the WAAS correction data if your view of the southern horizon is limited, which limits use of the correction data. The handheld units I've looked at, as well as the Ambit, receive the signal from satellites, not directly from ground based stations. Is EGNOS different?
> 
> Hmm, I've not looked in to this. The video makes it look like a problem with some Garmin units though, not a general 1m behavior with gps. (In my opinion)


WAAS/ EGNOS is based on ground station error correction and that signal is then broadcast by geostationary satellites. WAAS is US based, EGNOS is European and MSAS is Asian.

_"WAAS consists of approximately 25 ground reference stations positioned across the United States that monitor GPS satellite data. Two master stations, located on either coast, collect data from the reference stations and create a GPS correction message. This correction accounts for GPS satellite orbit and clock drift plus signal delays caused by the atmosphere and ionosphere. The corrected differential message is then broadcast through one of two geostationary satellites, or satellites with a fixed position over the equator. The information is compatible with the basic GPS signal structure, which means any WAAS-enabled GPS receiver can read the signal."_ - Garmin.

The video shows a problem with the software related to the manufacturer trying to filter the "noise" or inherent inaccuracy of 1m resolution. The software filters these low speed spikes as noise and shows the position as stationary when in fact they are moving.

This inaccuracy is a problem related to all manufacturers...just their software tries to deal with it in different ways. Regardless, in order to get an accurate direction and speed of travel for any consumer GPS, you need to be travelling at a speed greater than the resolution of the receiver/ sampling rate. Worst case scenario, you need to be travelling greater than 1m/s for the Ambit....1m resolution per 1 sec sample rate = 3.6kph or 2.23mph.


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## cobrapa (Mar 15, 2012)

Good edit.  I was about to comment on the original version. It sounds like we'll just have to disagree. I don't agree that the 1m absolute accuracy spec impacts direction measurement the way you say. At least not for some consumer grade gps units I've used. A couple of them can indicate direction changes with around a foot or less of movement. This is what I expect for the way gps is designed.

It's interesting to look at how differential GPS and some of the surveying/construction systems work. They claim corrected gps accuracy down to around the cm range. (Not using WAAS, but local differential GPS.)


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## Mystro (Oct 26, 2008)

This is a good discussion but my head is starting to hurt following the technical aspects. Let's dummy this down for the recreational GPS user. As a recap, What is the deficiency or problem of the application of the Ambit's speed accuracy?? Am I to only understand it is only erratic at speeds 2.8mph and lower and is only visible on a detailed graph on Movescout?? I am familiar with the Garmin sticky GPS at low speeds and the Ambit doesn't have it. I tested for that the first day I got the Ambit.


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## theotherphil (Nov 2, 2009)

agreeing to disagree is fine. Have a test for yourself....go and place your GPS unit outside under the clear sky in a fixed position for 10 mins after it has a GPS fix. Download the track log and have a look. I've just done the same with a Garmin Legend HCx and I get:

Elapsed time: 10:13
Distance Covered: 50m
Average speed: 0.3kmh

That is when it was placed on a flat surface, clear skies and 10 satellites fixed. It is showing movement when there is none.

Same test repeated with the Ambit. Using trekking profile but with it customised to a 1s GPS Fix and no fusedspeed. GPS fix, placed it on a flat surface and waited 60s. I then hit the start exercise button:










That's quite a lot of variation for a device that is in a single location. The reason is because of a high sample rate, slow or no speed and a 1m CEP (Circular Error Probable) accuracy resolution.

Please, have a go with any GPS unit of your choice....place it in a single position with good GPS fix and have a look at the track log over a 10 minute period of zero movement.


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## theotherphil (Nov 2, 2009)

Mystro said:


> This is a good discussion but my head is starting to hurt following the technical aspects. Let's dummy this down for the recreational GPS user. As a recap, What is the deficiency or problem of the application of the Ambit's speed accuracy?? Am I to only understand it is only erratic at speeds 2.8mph and lower and is only visible on a detailed graph on Movescout?? I am familiar with the Garmin sticky GPS at low speeds and the Ambit doesn't have it. I tested for that the first day I got the Ambit.


OK, assuming best case scenario....multiple satellite fix, WAAS correction, clear skies, perfect weather etc you will get an accuracy of 1m. Basically, your reported position can be anywhere in a circle of 1m from your current position.

If you have a sample rate of 1s, a GPS fix is recorded every second. That next fix can be anywhere within 1m of the initial fix...potentially indicating a movement of 1m/s even when stationary.

In order to overcome this, by that next GPS fix you need to be greater than 1m away from the previous one...the further the better. With a 1second sample rate, in order to move that 1m, you need to be travelling 1m/s or greater (3.6kph/ 2.23mph).

2 things can be done to smooth your results....move faster or increase the time between samples.

At running pace of 9mph/ 14kmh, a 1s sample time will put you a distance of approx 4m away from your previous fix.

To achieve this same distance at a reasonable walking pace of 3.6kph, a 4 second sample time should be used to achieve the same "smoothness" to the graph.

For walking speed, a 1s sample time is too fast to produce accurate reported results in both distance and speed. This is due to the 1m resolution accuracy of GPS.

Remember, these devices are not using "snap to road" like automotive GPS...you can literally be anywhere within that 1m circle from one fix to the next.


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## Mystro (Oct 26, 2008)

theotherphil said:


> That's quite a lot of variation for a device that is in a single location. The reason is because of a high sample rate, slow or no speed and a 1m CEP (Circular Error Probable) accuracy resolution.
> Please, have a go with any GPS unit of your choice....place it in a single position with good GPS fix and have a look at the track log over a 10 minute period of zero movement.


O.K I just did this test. Set my Ambit on 1 second GPS recording and sat it on my back deck for 11 minutes. My watch summery and Movescout showed I didnt move at all. It showed very little if any floating of position.


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## theotherphil (Nov 2, 2009)

Mystro said:


> O.K I just did this test. Set my Ambit on 1 second GPS recording and sat it on my back deck for 11 minutes. My watch summery and Movescout showed I didnt move at all. It showed very little if any floating of position.


What profile? Running profile will use fusedspeed. This is using the accelerometer to remove this error in the GPS signal. It senses no movement so discounts the GPS reported movement. Do the same test with the cycle profile which has a 1s sample time and no fusedspeed.

If you are walking at a slow pace with the running profile selected, you will not be generating enough movement as you would when running, therefore some of the results are discarded by fusedspeed as erroneous data (hence the spikes down to zero)....it thinks that the movement is error in the signal and that you are not moving when you are.

At these slow walking speeds, a longer sample time is needed (this is why the trekking profile is set at 60s without fusedspeed).


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## Mystro (Oct 26, 2008)

I was using the Motorsport profile that doesnt use Fusespeed. I set the profile up for ATV/Motorcycle riding. Fusespeed was not a factor.











theotherphil said:


> What profile? Running profile will use fusedspeed. This is using the accelerometer to remove this error in the GPS signal. It senses no movement so discounts the GPS reported movement. Do the same test with the cycle profile which has a 1s sample time and no fusedspeed.
> 
> If you are walking at a slow pace with the running profile selected, you will not be generating enough movement as you would when running, therefore some of the results are discarded by fusedspeed as erroneous data (hence the spikes down to zero)....it thinks that the movement is error in the signal and that you are not moving when you are.
> 
> At these slow walking speeds, a longer sample time is needed (this is why the trekking profile is set at 60s without fusedspeed).


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## cobrapa (Mar 15, 2012)

Interesting data. I've not tried this, but I will.

Are you sure the Garmin's aren't just junk GPS's? :-d (I own a couple Garmin's, so I'll take a look as well.)


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## pjc3 (Mar 26, 2012)

cobrapa said:


> Your first graph is interesting... Where you walking a consistent speed? That speed graph varies quite a bit!


Yes, 3 loops all at roughly same pace. That was the point to see if Fusedspeed helped at walking pace or not. It is interesting to note that even if the "GPS fix and recording rate" is set at 1sec and the "recording interval" is 10sec, the graph for speed (as posted) is only updated every 10sec. I assumed the recording interval (of 10sec) would be for other parameters such as altitude and HR and the speed would still be 1 sec intervals.


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## rkendall (Apr 1, 2012)

Where you swinging your arms during your walk, not jogging style just a normal pendulum movement. I found that could cause my speeds to jump all over the place but when I held the watch steady it was much smoother for non fusedspeed activities.


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## Ian H Clode (Apr 8, 2012)

I hate to say this, i bought one of the first Sunnto x10 and i had all the problems with it the top bezel came detached from the case, as well as delamination of the black coating, the battery life deteriorated..i sent it back to sunnto three times on the third visit to sunnto i came across a thread detailing all theses faults.. i quickly sent a letter to Sunnto complaining about what was clearly well know faults....they admitted that they had stopped production of the x10..

I must say after a letter fo complaint supported with evidence...not that sunnto were going to volunteer the information, they exchanged my old x10 witha brand new one.

I have read the write up of the ambit, i would love one! but does it do what it says on the tin? i have three sunnto's a core a vector an advisor and an x10, trust me i am a sunnto lover.........but i have put off getting an ambit untill at least a year has gone by to see if this watch is all its made up to be


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## Goost (Mar 26, 2012)

How can I switch Fuse Speed on??


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## cobrapa (Mar 15, 2012)

FusedSpeed depends on profile as picked in Movescount/your exercise. You can see if it is enabled on the website by looking at the profiles 'Advanced' settings section. By default it's on for profiles where you'd expect to swing your arm (Running, Walking, Trail Running, etc...) and off for other stationary arm activities (Biking...). In the current Movescount setup, I think you can only change it by setting the activity type to one that enables FusedSpeed.


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## pjc3 (Mar 26, 2012)

FusedSpeed is *not* activated for Walking profile.


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## cobrapa (Mar 15, 2012)

My Movescount account never had a walking profile.... :think:

Oddly, the walking activity does not enable FusedSpeed, but the Orienteering activity does.


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## pjc3 (Mar 26, 2012)

I run when orienteering.


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## cobrapa (Mar 15, 2012)

Maybe that's why. I've never done a speed orienteering competition, but I know some do that.


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## Suunto Team (Apr 11, 2012)

We hope the clarifications below will answer most of the questions posed in this thread 

*Swinging of the arm can cause error in track and speed*
GPS watch (with a GPS receiver) that is attached to arm measures the arm speed. Arm speed is not same as the actual walking speed. Arm speed is the walking speed plus the speed of the arm swinging relative to the body. So when arm swings forward the arm speed is higher than actual walking speed, and when arms swings backwards the speed is lower than the actual walking speed. When walking, arm typically swings back and forth once per second.

Suunto AMBIT uses SIRFSTAR IV GPS receiver that measures location and speed once per second. It can happen that the GPS receiver measures its speed for instance when arm is swinging backwards. In this case the measured GPS speed is smaller than the actual walking speed. After one second GPS receiver measures the speed again and if arm is again swinging backwards the measured speed is again smaller than the actual walking speed. The GPS receiver can thus measure for a long period speed that is smaller than the actual walking speed. Since this bias like error due to swinging arm can appear for a long time, then the adaptive filtering of the FusedSpeed can't take the error away completely. However adaptive filtering of the FusedSpeed will reduce the error. This error varies in magnitude depending on in which phase of the arm swing the speed measurement is taken.

*The issue is typical with walking speeds, but disappears with jogging/running speeds*
Technical term for above mentioned phenomenon is aliasing. Aliasing effect is the strongest when arm is swinging approximately at same interval as measurements are taken. This is the case typically during walking. When the swing frequency increases the effect becomes smaller and thus this error is not as clearly visible in running than in walking. In addition to the change in arm swing frequency, typically the length of arm swing is also smaller in running compared to walking. The issue of aliasing typically disappears with jogging/running speeds equal or higher than 7km/h.

*FusedSpeed in a nutshell*
FusedSpeed is GPS speed that is adaptively filtered based on the accelerometer data. This means that the GPS speed filter tightness is controlled by the accelerometer based running/walking speed. When accelerometer shows that user is walking/ running at even pace the GPS speed filter is tight and it removes most of the random error in GPS speed. However, if GPS speed contains very large errors then some of this large error will come through. However, error will be reduced considerably by the tight filter allowed when using the sensor fusion. In addition, if the accelerometer detects speed changes, it will reduce filter tightness and allow less filtered GPS speed to come through.

*FusedSpeed improves speed accuracy also with low speeds*
FusedSpeed improves the speed accuracy of the GPS also in slow walking speeds. However, since the effect due to aliasing (see above) can be very strong - measured speed varying between zero and double in comparison to the actual walking speed - FusedSpeed functionality is not able to compensate/remove this aliasing effect totally.

FusedSpeed is dedicated to be used in running/walking -like sports only (e.g. walking, running, trail running, hiking, trekking, multisports, triathlon,) and is a pre-configured default-functionality in the Movescount.com when selecting/creating one of the above mentioned sports modes. Suunto has now added an indicator for FusedSpeed and made it visible in Movescount.com/GEAR/Customization/Advanced settings of a sports mode to indicate if the FusedSpeed is in use in the specific Sport Mode or not.

*Our recommendation*
For Suunto AMBIT users exercising by walking with slow speeds, Suunto recommends to select the Trekking -sports mode from the AMBIT's exercise menu when starting the exercise. This sports mode uses 60sec GPS fix-interval and thus provides steady, but accurate enough speed readings when moving slowly. User can also create a dedicated sports mode for walking in Movescount.com and name it "Walking" and select the 60sec GPS fix interval from the Advanced Settings -menu in the GEAR/Customization -section of Movescount.com


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## wydim (Feb 26, 2012)

Suunto Team said:


> We hope the clarifications below will answer most of the questions posed in this thread
> 
> *The issue is typical with walking speeds, but disappears with jogging/running speeds*
> Technical term for above mentioned phenomenon is aliasing. *Aliasing effect is the strongest when arm is swinging approximately at same interval as measurements are taken*. This is the case typically during walking. When the swing frequency increases the effect becomes smaller and thus this error is not as clearly visible in running than in walking. In addition to the change in arm swing frequency, typically the length of arm swing is also smaller in running compared to walking. The issue of aliasing typically disappears with jogging/running speeds equal or higher than 7km/h.


For the french speaking people, aliasing is "repliement spectral" or "fréquence de repliement". When the sampling rate is approximattly equal to the frequency of the arm swinging, you loose sight of what happens in between the same and continuous backward (for example) swing.

But I have a question for the Suunto team. A GPS is basically not a speed measuring instrument. It only takes fixes at different locations at different points in time. Then the speed is derived by dividing the difference in meters between 2 fixes by the time between the 2 readings. Now... maybe it's already done with the fusespeed accelerometer, but.. why couldn't the watch-gps, let's say every 10 or 15 sec, derive the speed from a Delta(time=15 s) and compare it with the instant speed (delta(time=1s)).

edit : the fusespeed is an accelerometer, it really measures the acceleration to filter the speed. What I'm talking about is purely simple calculus : use an average speed between 15 sec now and then to compare to the 1s interval speed, no accelerometer required.


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## cobrapa (Mar 15, 2012)

It's great to see Suunto here posting detail about Ambit speed, thank you!


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## or_watching (Nov 13, 2008)

For additional reference, here is data from hike with another SiRFIV-based watch. Mostly under tall fir trees.
a) spikes are a given at hiking/walking speed, when viewed on the graph, if you've collected data at 1sec intervals.
b) The amount of smoothing in the chart is critical to what you see in a later review. I don't know what Movescount uses, and I don't think it's user-configurable. (it should be)

Not EVERTHING is a 'spike', like where I punched thru the snow near the summit and took 5 minutes to get myself out. 

*NON-AMBIT SiRFIV* DATA
40point smoothing








20 point smoothing








10 point smoothing








No smoothing


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## XCJagge (Mar 1, 2012)

As far as I know GPS measures speed directly and those speed readings are more accurate than speed figures calculated by using saved track points. I believe with 1 sec fix Ambit uses speed readings, and ti does not calculate speed using saved points as or_watching did here (I think). Unfortunately if you take one reading per second can your arm may be always swinging forward. Or backwards. Anyway, for some 60 sec fix interval is rather poor workaround because some of us may like to get better track log than the one point per minute one. So now for walking you kind of need to select between poor track log or poor pace readings.


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## jkm00 (Mar 13, 2012)

As pointed out the GPS samples are current location not current speed so I do not buy the Suunto description of why the problem occurs but I agree on the result of the problem and the solution, longer time between samples will make 'average' speed closer to real speed. I wrote this in another thread:

_I don't think arm movement is such a big issue. Biggest problem is that (non-military)GPS is inherently not more accurate than 1m. So if you move 1m per second, have accuracy of one meter and 1s sampling rate you can get sample 1 and 2 anywhere between 0 and 2m apart, i.e. speed between 0 and 2x real speed (only taking into account the speed in the direction you move, you also have a sideways error where you can be 1m left in sample one and 1m right in sample 2). So all this then have to be smoothed out with filters to get reasonable numbers. But if you smooth too much you will not catch changes in pace buth then the Ambit has the fusedspeed to help._

With 60s sampling rate you will only get 1m error in each sample point but the error will then be very small compared to the total distance traveled, e.g. 30 meters/60s would then have an GPS error of +/-2m. 
With 1s samples each sample will have the error described above but the average speed for e.g. 1km will be ok, so the problem is spiky graphs that look bad and are hard to read for e.g. tempo changes going uphill/downhill or intervals. With GPS accuracy being what it is I belive that 1s samples are too optimistic and that it needs to be filtered more than what is done today and it would also be good to be able to have e.g. 2s or 5s GPS sampling interval. I do not know sampling rate in Iphone or Garmin but if they sample with longer intervals (2, 5, 10s?) then the average speed during that period will have a smaller error by default, they most likely filter more too.

Seriously, the graphs above from 'or watching' looks like crap.
_
This being my first GPS watch I am not very impressed with the accuracy of plotting my movement on roads and trails on the map, i.e. ususally plotted a bit to the side. I think that this can also be made better with some updated algorithms.. (and it would not surprise me if Garmin is a bit better on GPS as they have a longer track record there). All in all I like the Ambit really much, would not trade it for a Garmin, but some things can be improved._


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## Lost-again (Feb 24, 2012)

jkm00 said:


> As pointed out the GPS samples are current location not current speed so I do not buy the Suunto description of why the problem occurs but I agree on the result of the problem and the solution, longer time between samples will make 'average' speed closer to real speed. I wrote this in another thread:
> 
> _I don't think arm movement is such a big issue. Biggest problem is that (non-military)GPS is inherently not more accurate than 1m. So if you move 1m per second, have accuracy of one meter and 1s sampling rate you can get sample 1 and 2 anywhere between 0 and 2m apart, i.e. speed between 0 and 2x real speed (only taking into account the speed in the direction you move, you also have a sideways error where you can be 1m left in sample one and 1m right in sample 2). So all this then have to be smoothed out with filters to get reasonable numbers. But if you smooth too much you will not catch changes in pace buth then the Ambit has the fusedspeed to help._
> 
> ...


You may have a fault, it is possible. From the testing I have done my Ambit tracks my location with better accuracy than anything I have had before and I own many gps devices. If you are comparing it to a car gps they fudge the result by using a "snap to" function, which moves the location to the nearest road. You cannot do this with the Ambit because it has no map database, anyway your not likely to find roads in a lot of the places Ambits will go  I also have a Garmin and it is no better and in most cases worse (though not by much) so this really is as good as it gets! Technology in this area has already come a long way, but it is like computers it just keeps improving. It can tell you where you are (within 1m in most cases), where you have been and as long as you are moving reasonably quickly how fast your going, so does what it says on the box!
I would not challenge you find an equivalent because they are out there, but better, now that would be a challenge and the Ambits ability to achieve a lock and hold onto it, is the best I have currently seen in a unit of this size. In the future who knows what will hit the market?


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## or_watching (Nov 13, 2008)

My post was for a reference in people commenting on their pace graphs in movescount. And I'm just making the point that what you observe there is affected by graph smoothing choices - and I don't think we know Movescount does or doesn't do. Certainly ther's opportunity for a lot of clever post-processing as people get PhDs in exactly this stuff. 

Other than Suunto's comments, I dont know anything about their in-watch algorithms for reporting pace. E.g with FusedSpeed off do they apply any filtering/averaging and is it different paced on pace and on fix interval. 
I wouldnt be surprised if that you see in-watch is somewhat different than in a Movescount graph of the same event. 

And yeah, those graphs look pretty crappy. That's why the concept of integrating the accelerometer data in the on-wrist pace reporting is so interesting. I guess the verdict on the practical benefit is still pending.


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## idgsd (Apr 21, 2012)

I had a chance to do several walks with the Ambit and several other GPS watches I own (Garmin FR110, Timex Run Trainer) and handheld (Garmin Etrex 30) on previously measured (Google Earth) open and relatively flat street tracks. There is no doubt in my mind that distance-wise the Ambit is the least accurate of them. I tried it in several profiles with FusedSpeed and without, 1s GPS fix (similar to the other devices) and both 1s and 10s recordings. One just needs to look at the downloaded tracks from all the devices to recognize that the Ambit tracks contain much more lateral and other zig-zag movements compared to the other devices. Both Garmin and Timex filter the data to show smoother tracks that match better the actual paths. All the other devices agree fairly well within +/- 1% distance accuracy, while the Ambit tend to measure long by as much as 2-4%. Since the Ambit GPS sensitivity is definitely as good as the other watches, the Ambit needs to apply better filtering algorithms to its recording/measurements. Also, it would be nice to be able to program more options to the recording and GPS fixes intervals (say 5s, 10s, 20s, etc.)


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## pjc3 (Mar 26, 2012)

I concur. The Ambit "drifts" almost rhythmically.

Ambit vs iPhone.








Guess which is the Ambit? (And no I wasn't inebriated at the time :-d )


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## cobrapa (Mar 15, 2012)

Pretty interesting, how fast where you going for this Ambit and iPhone map?


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## idgsd (Apr 21, 2012)

Ambit (blue) vs. Timex Run Trainer (red). Seems like Ambit's GPS data needs some processing.....Steady walking pace of about 3.7 mph


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## Jeff_C (Feb 11, 2006)

These are very interesting!


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## cobrapa (Mar 15, 2012)

idgsd said:


> Ambit (blue) vs. Timex Run Trainer (red). Seems like Ambit's GPS data needs some processing.....Steady walking pace of about 3.7 mph


Agree, very interesting. Is this at the same time? Or are these two traces on different days?


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## paduncan (Sep 28, 2007)

At least for running, the Ambit is solid for me - comparable to my Garmin FR 610.

610 is top, Ambit is bottom. Both of these routes out and back, on the same sidewalk, so you can see how tight both tracks are.


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## idgsd (Apr 21, 2012)

cobrapa said:


> Agree, very interesting. Is this at the same time? Or are these two traces on different days?


The tracks are simultaneous, Ambit on the left wrist and Timex on the right....Ambit in the running profile (as far as the track accuracy, I did not see any improvement compared to the walking profile), both are 1s GPS fix, 1s recording.


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## idgsd (Apr 21, 2012)

After the positive reports by paduncan and others about the Ambit run accuracy I went out on a run-walk combo. I ran a short street track (7+ mph), shown on the bottom, and walked back (3.5+ mph), shown on top. Clearly, the run recorded track is smooth while the walk is not. Apparently Suunto applies some speed sensitive filtering, which does not work well at walking speeds (even brisk ones).


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## Jeff_C (Feb 11, 2006)

Again, that is really interesting. As you state, you can clearly see a difference in the two. Hmm, I guess it does the same thing hiking?


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## rkendall (Apr 1, 2012)

Its good to see some validation, after arguing with Suunto they were making me feel like I was crazy (which lead to their posted response on the forum) so far they are unwilling to admit there is anything wrong with how they do walking/hiking filtering. And I don't accept there answer of just take a 60 second fix as a reasonable solution, if I'm hiking for 2-4 hours I should have more than 60 second track points. Hopefully as other report this they will fix it sooner rather than latter.


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## idgsd (Apr 21, 2012)

rkendall said:


> Its good to see some validation, after arguing with Suunto they were making me feel like I was crazy (which lead to their posted response on the forum) so far they are unwilling to admit there is anything wrong with how they do walking/hiking filtering. And I don't accept there answer of just take a 60 second fix as a reasonable solution, if I'm hiking for 2-4 hours I should have more than 60 second track points. Hopefully as other report this they will fix it sooner rather than latter.


I sent them a couple of my previous tracks and included as a reference my Timex Run Trainer simultaneous data. I just received an e-mail from them trying to clarify the GPS fix and recording intervals. I replied and attached this morning's track, as it is quite evident that their algorithms work poorly for lower speed movements. I am in full agreement with you that the 60 sec track points solution is completely unacceptable and an insult to their customers and their brand. I can understand that they may not possess the experience and expertize of Garmin and may have to go through some learning curve with GPS technology, however Timex is not a GPS household either and were able to figure it out reasonably well in a watch which is about 1/3 of the price of the Suunto.


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## or_watching (Nov 13, 2008)

Don't put Timex and their run trainer on too high a pedastal. 

I have a timex run trainer. Pace and track are fine when running. I guess the instantaneous pace report could still be smoothed a bit more for my liking. 
I took it on a couple of hikes of well-known distance. The distance reported in the watch during the hike and in the watch summary were short by 30%. Both times. In software afterwards the track is fine and Software reading the track computes the correct distance. So, the've got some algorithm problem too. 

So it's useless on a hike. 

But what really got me was the did not reply to Support emails from me. The Training Peak guys, to THEIR credit are super responsive. Biut the conclusion was its an issue in the watch. Yep, all the firmware is up to date etc. 

My Run Trainer is now for sale. 

And if I recall the 910xt has had significant acknolwledged problems at low jogging speed Pace reporting. I'm not sure how bad it is at walking/hiking speeds. I havent checked those forums to see if they have patched it yet. 

At least Suunto is talking to us generally, and replying individually. It's better than the squat bubkus I got from Timex.


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## paduncan (Sep 28, 2007)

I will have to do a walk soon to validate this on my end. I will use trekking mode, but keep the sampling rate to 1 second...


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## bowesmana (Apr 22, 2012)

I noticed a similar speed variation yesterday. I did a 21km trail run after a 1 hour cycle, so had pretty heavy legs and was power walking rather than running the hills, but the speed is all over the place. I also wore my t6c + foot pod and that graph has far fewer 0 km/h speeds.

This is the Ambit log









and this is the t6c









It does seem odd that Suunto does not currently support the foot pod given the apparent limitations with an arm based accelerometer.


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## XCJagge (Mar 1, 2012)

idgsd said:


> View attachment 688062
> 
> 
> After the positive reports by paduncan and others about the Ambit run accuracy I went out on a run-walk combo. I ran a short street track (7+ mph), shown on the bottom, and walked back (3.5+ mph), shown on top. Clearly, the run recorded track is smooth while the walk is not. Apparently Suunto applies some speed sensitive filtering, which does not work well at walking speeds (even brisk ones).


I don't think there is any speed sensitive track filtering. I suspect GPS Ambit's antenna is quite directional and needs to be shooting up. When you walk your antenna is not shooting up as well as while running and I believe this makes the difference. This is based on my tests, when I run I get far better accuracy if I wear ambit a bit differently, I wrote about it here https://www.watchuseek.com/f233/ambit-vs-iphone-677321.html#post4943597
I believe this happens because antenna picks reflections from ground/houses/trees at the direction antenna is shooting instead of those direct signals from the satellite, just because those signals are far stronger for the directional antenna. I got rid of the problem by wearing it as I wrote, antenna stays shooting better and my body filters reflections if the antenna turns to right too much. And my arm filters ground reflections from left.

You can try this by yourself. Make out and back run first with the device normally and then carry it as I wrote. And then compare how close out and back tracks are. It makes difference. If you carry it normally track is off to the direction antenna was shooting, if you wear as I described the track is pretty much spot on.


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## jkm00 (Mar 13, 2012)

Here is from a run last saturday, four passes on the track through the forest. Two tennis courts for size reference, i.e. lines are off by 5-10m and not consistent. Running speed ~5:20/km. The accuracy is NOT any better with when running on roads with clear sky.

It is off to my left so XCJagge might be on to something when it comes to the direction of the antenna.. Looking through my old runs it seems like they are all off to my left in different degrees.. Will try to think about that next time.


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## idgsd (Apr 21, 2012)

XCJagge said:


> I don't think there is any speed sensitive track filtering. I suspect GPS Ambit's antenna is quite directional and needs to be shooting up. When you walk your antenna is not shooting up as well as while running and I believe this makes the difference. This is based on my tests, when I run I get far better accuracy if I wear ambit a bit differently, I wrote about it here https://www.watchuseek.com/f233/ambit-vs-iphone-677321.html#post4943597
> I believe this happens because antenna picks reflections from ground/houses/trees at the direction antenna is shooting instead of those direct signals from the satellite, just because those signals are far stronger for the directional antenna. I got rid of the problem by wearing it as I wrote, antenna stays shooting better and my body filters reflections if the antenna turns to right too much. And my arm filters ground reflections from left.
> 
> You can try this by yourself. Make out and back run first with the device normally and then carry it as I wrote. And then compare how close out and back tracks are. It makes difference. If you carry it normally track is off to the direction antenna was shooting, if you wear as I described the track is pretty much spot on.


It is an interesting and plausible explanation, even though intuitively I don't think so. However, on my next walk, I'll put the Ambit in my shirt pocket with the antenna facing up the whole time and see what happens. I love the Ambit's GPS sensitivity and fast acquisition time. If it achieved by making the antenna more directive it may be missing the point. When I hike, I don't want to be constantly thinking about my arm position.....I believe that the smoother tracks I get from other GPS watches I own (Garmin FR110, Timex Run Trainer) and my iPhone 4s, are the result of the way the data is processed.


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## pjc3 (Mar 26, 2012)

After a weekend of walking, I really hope Suunto change the GPS fix & recording rate to include a 10sec interval. 60 seconds is just too long and of course 1sec is not appropriate for walking. Using the 60sec record rate the resulting track had many corners cut off and the whole walk (over 16km in 4.5hrs) came up short compared to iPhone. I'm not sure what the T6c and GPS pod recording interval is but it seemed more accurate (using iPhone as the standard).
60sec may be a good compromise for batterylife for multi-day trips but I still would like an option for intermediary trips.


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## or_watching (Nov 13, 2008)

I wonder how much battery life benefit there would be for a fix rate of 10s. Since the stated battery life only triples from 'continuous' to '60s', my hunch is that at '10s' you'd only get a very small battery life improvement. 

But I get what you're saying. Depending on your walking/hiking speed and the trail itself, 60s won't always be a good rate. 
Maybe 30sec would give '2x' the battery life (25-30hrs), and reduce the track errors enough. 

And for sure for memory recording time would benefit from being able to pick track intervals other than 1 sec, even when using continous fix, makes a lot of sense. My handhelds do that. 

And my 60csx is my gold standard. 
I haven't looked, but do any handhelds nowadays offer a battery-save feature like the Ambit by powering GPS reciever off/on?


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## idgsd (Apr 21, 2012)

pjc3 said:


> After a weekend of walking, I really hope Suunto change the GPS fix & recording rate to include a 10sec interval. 60 seconds is just too long and of course 1sec is not appropriate for walking. Using the 60sec record rate the resulting track had many corners cut off and the whole walk (over 16km in 4.5hrs) came up short compared to iPhone. I'm not sure what the T6c and GPS pod recording interval is but it seemed more accurate (using iPhone as the standard).
> 60sec may be a good compromise for batterylife for multi-day trips but I still would like an option for intermediary trips.


The 1 sec recording is appropriate for walking, if battery life is not an issue. Each GPS fix read has a location error of several meters, even under clear sky. The more reads the GPS makes, the better the potential accuracy one can get. The secret is in the design of processing algorithms that filter the noisy reads and at the same time accommodates the dynamics of ones activity. I think each one of my other GPS watches and handheld devices, has 1 sec GPS fix interval. Their distance measurements accuracies vary, but it is generally below 1% of the total distance. The Ambit, despite its excellent GPS sensitivity, does not measure distance accurately on my walks, especially when I wear it on my wrist (independent whether it is in the running, walking or trekking modes). On the otherhand, when I put it in my shirt pocket with the antenna pointing up, it is much more accurate and its tracks are much smoother.


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## Mystro (Oct 26, 2008)

I believe a 30 second GPS record time is a natural progression. 1, 30, 60 seconds would be perfect fot all activities. I think there is a little too much of a gap between 1 and 60 second record interval that some activities might not be appropriate.
30 seconds would be great for woods running.


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## viatormundi (Dec 24, 2011)

I had a Stand Up Paddle session lately and recoded the workout with Ambit and Iphone Sports Tracker App. I used the Kayak mode in Ambit. Recording interval and GPS recording rates are 1s and FusedSpeed is off. The speed graph of Ambit has many spikes and the max speed was 12.6km/h vs 8.39km/h in Iphone?? The average speeds were quite close. Since I am moving my arms a lot while paddling should I FusedSpeed or use a 60s interval?


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## or_watching (Nov 13, 2008)

viatormundi said:


> I used the Kayak mode in Ambit. Recording interval and GPS recording rates are 1s and FusedSpeed is off. The speed graph of Ambit has many spikes and the max speed was 12.6km/h vs 8.39km/h in Iphone?? The average speeds were quite close. Since I am moving my arms a lot while paddling should I FusedSpeed or use a 60s interval?


just eyeballing the graphs, the iPhone graph looks like it has fewer data points. So effectively it's smoothed vs the Ambit at 1sec. The Ambit at 60sec would have even less data. Would that be better? Depends on how straight vs zig zaggy your path was.

hard to say say which setting would be ideal. But it would be nice if the Ambit had a few more Track point options. Or at least a smoothing display option in Movescount.

From what I've read, FusedSpeed is currently only 'tuned' for running.


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## pjc3 (Mar 26, 2012)

We have asked for intermediate sampling time for "slow" (ie < 10km/hr) activities. Whether Suunto do it is another matter. I am hoping in FW 2.0 but unlikely IMO. Others argue that Movescount should be able to re-sample the data to smooth things out.

Anyway below is what happens with Ambit vs iPhone on same track. The longer sample time on iPhone makes for a more "accurate" track and speed. As you say, average speed is still acceptable on the Ambit but the instantaneous speeds must be taken with some caution.


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## viatormundi (Dec 24, 2011)

I move my arms a lot during paddling but the speed is around 9-10 km/h most of the time. Shall I activate the FusedSpeed to get more accurate data?


Sent from my iPhone using Tapatalk


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## pjc3 (Mar 26, 2012)

According to Suunto promotional material, fusedspeed is used when GPS signal is weak/lost. It probably won't be used in open water. My running profiles (fusedspeed active) is all over the shop like yours.


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