NokiaBetaLabs

Accuracy of total distance

Discussion for Sports Tracker

26-03-2009 11:11

Hello all

I've been using Nokia Sports Tracker for a few months now. I've noticed that it seems to over-measure all routes by around 5-10% compared to when I measure routes using web based measuring tools such as Gmap Pedometer ( http://www.gmap-pedometer.com ). A route I've measured as bang on 10k came out as 10.5k when I ran it.

I was wondering if anyone else has been seeing this or if the web site tools I've been using may be the inaccurate ones. I've noticed that when I zoom in on the run in NST the lines I've run down a straight road are a bit zig-zag as if the GPS inaccuracy is causing this but I'm not sure.

Thoughts anyone?

Ben

Comments

Submitted by mbrett on 26-03-2009 12:24.

My assumption is that the web site route generation is assuming point to point running whereas as NST logs where you actually ran. This is just my logic it could be wrong.

mbrett
N95 8Gb (Product Code: 0558787 (UK)) FW 31.0.018

Submitted by alunklrodgers on 26-03-2009 13:05.

I've done quite a few "Accurately measured" road races and more often as not, NST is within a few % of the quoted distance and generally compares very well with other GPS based solutions such as Garmins etc...

Without a shadow of a doubt, no GPS based device can be as consistently accurate as following the course with a wheel measure because of interference from trees, tall buildings or terrain.

Alun
N95-1 (Product Code: 0548170 (Orange UK)) FW 30.0.015

Submitted by benhorley on 26-03-2009 13:50.

Thanks for your comments.

I wonder who is "right" then. To me it's quite a big deal as + 5% is a massive difference, it's 500m (so for me around 3 minutes) for a 10k.

Mbrett, that's kind of what I thought so I suppose NST is the more accurate one. I know GPS is not totally accurate but I would have thought the discrepancies would have cancelled each other out.

I reckon the only issue with accuracy and distance could be that your location could jump around but you are really just running a straight line. For example, if you are running along a straight road, the GPS points won't be a nice straight plot, they'll be jumping left and right a few feet so instead of there being a nice straight line they'll be a zig-zag which will measure longer.

Alun, when you say "a few percent" what kind of numbers are you taking about, 2 or 3 / 7 or 8 / etc?

Maybe I'll just assume NST is right and go from there.

Submitted by mbrett on 26-03-2009 14:12.

If you want it more accurate you could purchase the Nokia LD-4W External Bluetooth GPS Receiver. See the topic below and the site quoted in my second comment.

http://betalabs.nokia.com/forum/topic/1386

mbrett
N95 8Gb (Product Code: 0558787 (UK)) FW 31.0.018

Submitted by djh.sthlm on 26-03-2009 14:18.

Don't use the "jagged" drawing of your workout on the NST website to draw final conclusions as to the accuracy of the original tracking data stored within the mobile app. NST website uses algorithms to summarize and "smooth" error spikes in the voluminous positioning data recorded from of the mobile app. The effectiveness of such are debatable.

If you export the data in GPX or KML format from your mobile app and view it in another application you will find a much more detailed route path.

As Alun stated above, there's little you can do to provide truly accurate distance measurements using GPS tech. Every time you use GPS you are faced with variables from satellites, weather conditions and other general obstruction interferences.

I run the same 5km route on rest days and using NST which can read between 4,7 and 5,5km. Similar result ranges are found when I use my Suunto and Garmin devices. Other times I've run as far as 24km with less than 1km in course length deviation.

In my experiences, pre-plotting a route using Google Earth's line/path measuring tool is nearly as accurate as Alun's suggested wheel measuring. I've double checked a few of my important routes against Google Earth using an odometer on my bike computer and the results are within a few meters.

-David

Current setup: e61 unbranded product code 0529654 Euro-B1 Silver. Firmware: 3.0633.09.04. Theme: Ovi blue. Service provider: 3 Sweden. Peripherals: Bluemax ext BT GPS module

Submitted by benhorley on 27-03-2009 11:14.

Thanks for all your responses. I suppose in a perfect world gmap-pedometer or Google Earth or whatever would match perfectly with NST but if I do then run once in NST I can then run against my previous run so the slight inaccuracies are not that relevant.

Submitted by djh.sthlm on 27-03-2009 12:34.

I always use a good old fashioned stopwatch, in my case a Polar wrist computer, for accuracy of timekeeping. Also, like I mentioned, measure a set route with odometer or Google Earth for a constant.

Then you can edit the time and correct the distance constant for each workout so that you can compare your workouts under routes organization more precisely.

-David

Current setup: e61 unbranded product code 0529654 Euro-B1 Silver. Firmware: 3.0633.09.04. Theme: Ovi blue. Service provider: 3 Sweden. Peripherals: Bluemax ext BT GPS module

Submitted by twynefever on 07-05-2009 23:36.

I didn't even know about this application when I got my E71, but have now found it to be incredibly useful whilst I start training for a half marathon later in the year. From having done a few different distance/routes i've found it to be both consistent and accurate (compared to tracking via google maps, etc). It's an application on a phone that compares incredibly well against purpose built devices. If you want something more accurate then buy one of them. For me this is more than good enough!

Submitted by gtamir on 15-05-2009 17:41.

I have Nokia E71.
I set in my garden and started the build in GPS program that comes with the E71, and the NST at the same time.

With the build in program I "moved" 100m.
It has 4 digits after the comma. which means for the last digit N 11.1m and for the last digit E 9.5m
The coordinates moved between 31.8024 N and 31.8025 N, and 35.1563E and 35.1564 E. only one digit each.

With NST I "moved" 490m.
It has 5 digits after the comma. Which means for the last digitN 1.1m and for the last digit E 95cm.
The coordinates moved from 31.80239N and 31.80259N, and 35.15628E and 35.15637.

All of this sitting in one place in the garden.

https://sportstracker.nokia.com/nts/workoutdetail/index.do?id=999051

Pity I didn't wear the Polar. I could burn a few calories.

I consider reporting a bug

Giora

Submitted by shawnfb on 13-06-2009 20:14.

I have been skating 6 miles.. by the time I am done the time is correct but shows I skate nearly 10 miles!. also when i start the application Sports Tracker.. 9 out of ten times..the speed starts off at a HUGE number.. like 945 MPH.. as an example.. then comes down as i go this completely throws off everything.
any thoughts?

Submitted by gtamir on 04-07-2009 15:59.

I came up against an article about the correlation between GPSfiltering and the accuracy of the distance.
http://blog.gpsed.com/tips-advices/what-is-gps-filtering-option-in-gpsed...

E71 + LD-4W user
Lat: 31.80244N Lon: 35.15630