Lies, damn lies, and the Garmin 810

smacl

Ok, so I know the calorie counter is based on a random number generator written by a fairy on magic mushrooms, but the temperature stats for today were also rather fanciful; Headed off at midday back at 5, 21c average with a high of 34c. Now it felt hot on the Wicklow gap and no mistake, but AFAIK we don't get 34c in Ireland. Anyone else got temp stats from today.

Weepsie

It will give higher temps if left in direct sunlight apparently.

http://www.bicycles.net.au/forums/viewtopic.php?t=48016

Seweryn

smacl wrote: »

Ok, so I know the calorie counter is based on a random number generator written by a fairy on magic mushrooms, but the temperature stats for today were also rather fanciful; Headed off at midday back at 5, 21c average with a high of 34c. Now it felt hot on the Wicklow gap and no mistake, but AFAIK we don't get 34c in Ireland. Anyone else got temp stats from today.

Today the riding conditions were unusual, as it was a sunny day. Your Garmin was exposed to sunshine, got a lot warmer than normal when it stays in the shade, and as a result was showing high temperature figures.

godtabh

Mine had 31 degrees on it. Average of 17

NiallBoo

Met Eireann etc measure temperatures in shade and shelter.

If your garmin is in sunlight or wind, it'll cause the temperature of the unit to change. So while it'll give you a more-or-less accurate temperature for the unit, this isn't the same thing.

However...you're in the wind and direct sunlight yourself, so what it says on the unit MIGHT actually new closer to what you experience while riding.

BoardsMember

NiallBoo wrote: »

Met Eireann etc measure temperatures in shade and shelter.

If your garmin is in sunlight or wind, it'll cause the temperature of the unit to change. So while it'll give you a more-or-less accurate temperature for the unit, this isn't the same thing.

However...you're in the wind and direct sunlight yourself, so what it says on the unit MIGHT actually new closer to what you experience while riding.

Nothing that measures temperature will do so reliably when exposed to direct sunlight, particularly if its encased in plastic. Don't be too hard on your garmin!

Wishbone Ash

My 810 gave an average temp of 22 today on a ride from Galway to Sligo. It was displaying 27/28 at times but it wasn't that warm.

aimnburn

My 500 averaged 22 with a high of 25.6 on the Wicklow Way. Consistently displayed 23 when it wasn't 23

smacl

smacl wrote: »

Ok, so I know the calorie counter is based on a random number generator written by a fairy on magic mushrooms, but the temperature stats for today were also rather fanciful; Headed off at midday back at 5, 21c average with a high of 34c. Now it felt hot on the Wicklow gap and no mistake, but AFAIK we don't get 34c in Ireland. Anyone else got temp stats from today.

The calorie number is based on a simple model with a lot of assumptions. If your weight is wrong or some of the assumptions are wrong (ie . More wind resistance due to headwind) it will be way off.

I went over the Gap yesterday around 10 and my Garmin 810 read an average of 22 which is about right. It felt like a furnace however!

smacl

ronoc wrote: »

The calorie number is based on a simple model with a lot of assumptions. If your weight is wrong or some of the assumptions are wrong (ie . More wind resistance due to headwind) it will be way off.

I went over the Gap yesterday around 10 and my Garmin 810 read an average of 22 which is about right. It felt like a furnace however!

Calorie counter has me at between 900-1200 calories per hour for a 50 year old lad at 87kg of average fitness. My typical lunch time ride up to Glencullen comes out over 1,000 per hour, e.g. 24.2k, 415m climbing, over 1hr5 gave me 1215C. Now 1215C over 1hr5 is 1121C/hr which according to this site would come out as 311 watts average. As the last bloke up the hill when cycling, I'm guessing this is out by almost a factor of two. On the TacX power meter, I struggle to hold 230 watts for an hour, and even that needs calibrating. Hence the Garmin Calories fairy, who I suspect is mainly interested in making my feel good about myself

godtabh

Regarding the calories it's funny how sat Stava and Garmin give different results when using a power meter. Should be the same.

NiallBoo

smacl wrote: »

Now 1215C over 1hr5 is 1121C/hr which according to this site would come out as 311 watts average.

The formula on the website is for maximum energy available from the food you take in.

The turbo will measure what comes out through your feet.
They should be pretty different.

Think of it like the difference between your gross pay and your disposable income.

Edit: after reading that again I See that it does try and account for that...but it really is a complete guess (they arrived at that figure because it made the maths easy).
- i really wouldn't worry about it.

smacl

godtabh wrote: »

Regarding the calories it's funny how sat Stava and Garmin give different results when using a power meter. Should be the same.

Ah go on so, give us the numbers.

smacl

NiallBoo wrote: »

I really wouldn't worry about it.

I don't really, though the power figure on the turbo is great for pacing when chasing a time on a given course. Doesn't matter that its right or wrong, just that it is reasonably consistent from one day to the next.

Thinking of writing an app that shows you your progress while riding as pints of Guiness filling up, which you can reasonably consume post-ride and still break even for the day :pac:

jamesd

smacl wrote: »

I don't really, though the power figure on the turbo is great for pacing when chasing a time on a given course. Doesn't matter that its right or wrong, just that it is reasonably consistent from one day to the next.

Thinking of writing an app that shows you your progress while riding as pints of Guiness filling up, which you can reasonably consume post-ride and still break even for the day :pac:

You can do that on Garmins already, show you how many beers you have worked off so can drink.

Hauki

I actually was under the impression that the temp reading would be from weather service on the connected phone but apparently the units have their own temp sensors after all.

cdaly_

NiallBoo wrote: »

If your garmin is in sunlight or wind, it'll cause the temperature of the unit to change. So while it'll give you a more-or-less accurate temperature for the unit, this isn't the same thing.

However...you're in the wind and direct sunlight yourself, so what it says on the unit MIGHT actually new closer to what you experience while riding.

Wishbone Ash wrote: »

It was displaying 27/28 at times but it wasn't that warm.

Don't forget that wind-chill works on people, not plastic so you'll feel cooler than the garmin will while rolling...

Macy0161

godtabh wrote: »

Regarding the calories it's funny how sat Stava and Garmin give different results when using a power meter. Should be the same.

Don't have a power meter (yet :pac: ), but for cycling at least, with a HRM, both Garmin and Strava are ballpark the same for me.

Strava calories have come down on the bike since I went premium - I don't know whether that's coincidence. They are still high when I'm running, but I can't guarantee whether they allow different bike and run zones (they are different) or whether I just haven't updated it in Strava!

I'm inclined to believe my Garmin when in doubt, but even with up-to-date stats and a HRM it is still somewhat of a guestimate, so without it, it's definitely a guestimate! HRM in theory measures effort, so should in theory reflect head winds, road surface, etc.