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Logging activities: A question of trust

6 watchers
Jun 2012
10:29pm, 23 Jun 2012
3378 posts
Badger
Thanks Grep.
I should own up to having a low-level IOSH H&S qualification :) which I use to help manage bits of equipment which can be lethally dangerous if you don't know what you're doing. Broadly speaking, the point of H&S is not to stop you doing things, rather to make sure that you can do them in a way that avoids you, your colleagues, or random passing members of the public getting maimed, though it's common to find H&S officers who are either too in love with their authority or too risk-averse to do anything but ban stuff that looks risky. And if I am visualising your pyramid correctly, it sounds about as safe as building a house of cards to climb up! How are the bulbs changed now? A tower?
Jun 2012
6:13am, 24 Jun 2012
60962 posts
GregP
A tower, yes - which means getting someone in. You'll find many church buildings have blown lightbulbs in higher places these days. And fewer clergy, church wardens and lay ministers hobbling about on crutches.
Jun 2012
9:15am, 24 Jun 2012
891 posts
Lisa T
Hehe! I rather like strava myself. Probably cos I'm the only 'lady' that seems to cycle round here & get most of the QOMs! ;-) It gives me a chance to compare my cycling with other people that cycle in this area, so I know they're cycling the same undulations as me and I can see how 'good' or otherwise I am against their rides. It's not made me cycle any differently. My distance & max speed is usually fairly similar, although my bike computer is often quite different.
Jun 2012
9:43am, 26 Jun 2012
61020 posts
GregP
Bounce for the "Cycle 1000 miles in 2012" crew.
Jan 2013
10:16am, 28 Jan 2013
64922 posts
GregP
Bounce for the "310xt" crew.
Jan 2013
11:14am, 28 Jan 2013
7334 posts
Caterpillar
I have often wondered how Garmin does the distance calculations. Simple example - one degree on the surface of the Earth at the North Pole = 110.9 km

One degree on the surface of the Earth at Timbuktu = 111.3 km

If you assume the Earth to be a perfect sphere then any mathematical calculations of distance based on latitude and longitude will mostly be a little bit wrong.

If you calculate the positions in three dimensional space relative to the exact centre of the Earth (however you define that) and some satellites then you will still be a bit wrong because the Earth wobbles.

On top of that if you decide to add up all the one-second Garmin segments to get a total distance then you would include all the zigs and zags caused by minor errors from satellite signals bouncing off aircraft and buildings and so on, and you would end up with a much bigger distance.

However, if you do a bit of smoothing, and get the average position over 30 seconds and join with a straight line to the previous average position you end up cutting off corners and recording a much shorter distance.

So strava must have decided to use a different algorithm to work out distance from the algorithm used by Garmin, but nobody can ever say which is best.

All I know is that I have only ever run one officially measured race where the Garmin told me the distance was exactly what the race organisers said it should be.
Jan 2013
11:18am, 28 Jan 2013
64936 posts
GregP
Catters - do you use TP at all? Maximum speed (this is more of interest to cyclists, obv) often veries between GC and TP and strava - *but* TP shows a 'max speed for 2 secs, max speec for 5 secs' etc. Ditto peak heart rates. This (IMO) is immensely helpful.
Jan 2013
11:26am, 28 Jan 2013
7335 posts
Caterpillar
TP = Training Partner? I guess I don't use it. I only pretend to use it - just the Virtual Training Partner.
Jan 2013
11:59am, 28 Jan 2013
64946 posts
GregP
No, sorry, TrainingPeaks.

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About This Thread

Maintained by GregP
A sort of 'Why FetchEveryone is better than STRAVA' wire.
----

Last Sunday I cycled to church.

My Fetch log, which I trust beyond all possibility of doubt, tells me this:

17.07 miles, 1h19m46s, max speed 30.3mph

Garmin Connect, which one assumes is closest to the raw data, tells me this:

17.07 miles, 1h19m46s, max speec 30.3mph

This makes me very happy.

Now, gentle Fetchies, you may have seen or read or experienced strava recently, and been tempted, as I was, to 'dabble' and see whether it might be fun. strava taking data from the same source (my Garmin EDGE 800) tells me this.

17.1 miles, 1h20m48s, max speed 31.9mph

Interesting, eh?
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