Calculation of Energy

Mike Austin shared this question 1 week ago
In Progress

I have written a spreadsheet to analysis an exported csv file and I am interested in how you calculate the energy used. This should be proportional to weight. I have a calculation that sums walking energy, increase in potential energy and kinetic energy., As it happens, the result is not far off the Locus Map value, yet Locus Map does not know my weight. How do you calculate it?

Comments (11)

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Actually, I see Locus Map does have my weight - but I would still like to know how the energy is calculated.

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Good day Mike,

Locus Map currently uses two methods to compute consumed calories.

First is based on the known heart rate value (in case of usage of some heart rate chest belt). If HR value is not known, energy is computed based on predefined activity for a track and computed basal metabolic. Both methods anyway need to know your sex, age, weight. Both methods anyway need to know your sex, age, weight and height. These values may be defined in Locus Map in settings > Track recording > Personal details.

You did not know about this "Personal detail" dialog right? Then it seems to be too hidden in settings.

Also, one interesting topic (which was not yet used/implemented) is here: http://help.locusmap.eu/topic/what-are-the-parameters-used-for-calculating-the-calories .

If you have additional questions, feel free to ask.

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Thanks, but that did not explain how it is calculated. I have written a macro to read LocusMap csv files (now writing one for gpx files) and I am using an energy calculation based on data from BUPA. I have started with walking on a level, firm surface for which I fit a curve to the reference:

KJ = Weight*Time*(0.125888*v^3 - 0.532833*v^2 +0.951283*v + 2.471667)/1000

where weight is Kg, Time is secs, v is mph (funny mix of units, I know)

To this I add the increase in potential energy (mgh2-mgh1) and the increase in kinetic energy (½mv2² - ½mv1²), only considering increases in h and v. I sum these for all the track points to get a total for the track.

I will be incorporating other types of walking from the same site eventually.

What I wanted to know was the equations that you use. On an example walk, LocusPro calculates 1269KJ. I calculate 1485KJ, which is 1346KJ from walking, 85KJ from potential and 54KJ from kinetic.

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Exact equation?

In case of Locus, the method based on "not known Heart rate values" is the following:

The major complaint I see here is ignoring elevation changes as also mentioned in the second topic. Not sure yet, how to correctly add support for it here.

Is my explanation clear?

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Elevetion is only one of many unknown variables:

  • elevation
  • efficiency of the equipment (for example tires on bikes)
  • terrain
  • wind
  • pressure/oxigen level?

I guess if you don't have any power messurements (for example power meter on bike) every calculation isn't worth anything.


Just to show how far away our values are:

http://www.kreuzotter.de/english/espeed.htm

And even this is far away from correct values because there are many parameters missing as well.


I guess Locus maps isn't the right place to put 10 to 20 parameters in to calculate usefull energy values. An addon for energy calculation would make more sense?

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You are of course correct, but for every parameter you may define it's most probable impact. Only "crazy users" may expect that Locus Map will compute exact and very precise energy values. I had consider time and speed (together with values needed for basal metabolism) as the most important so the solution is based on these facts. The elevation is from my point of view next parameter, that is well known during computing! and that may have a significant impact. Mos of other parameters are completely unknown and as you wrote ... "Locus maps isn't the right place to put 10 to 20 parameters in".

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Acutally I don't know anything about energy calculation, but I got this crazy link from one of my friends. And wind makes more difference then altitute for road bikes.

I guess terrain and tires are the most expensive parameter for mtb.

I was just suprised that we do have this in locus. I used that opertunity to display energy on my elevation test tour just for fun: 23.471 KJ, well I guess I need to catch up on food consumtion to compensate last week ;)

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23471?? :). Week of running? If you see such huge value, there for sure have to be some explanation. Incorrect parameters in settings > track recording > profile or incorrect "activity" defined for your recorded track or some part of the track was maybe by car/bus but recorded into the same track?

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No, just a 10 hour 270km road cycle tour :D

This is my real word example for my elevation threshold testing.


I did just switch from walk to cycle that is even more:

29.268 kJ

Are you sure that cycling is more expensive then walking? I guess we do not calculate speed.

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270km/10h, then such huge consumption is logical I think.

Consumption: it depends. Cycling and also Walking has defined consumption based on it's speed. For example quick walk 1.6 m/s consume 4.3 x BRM. Average bike ride 4.9 m/s consume 6.8 x MET which I think is logical. In your case, you maybe ride on road bike and good road which is something completely different compare to 27km/h on MTB in dirty terrain. I know, many parameters ...

Suggestion: use these energy values just for overview information, not as something that should be used to plan your diet ;).

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Thanks, I will dig deeper into those references to find suitable equations for my macro. Then I will know how clear it is!

My equation is a simple curve fit to the reference I quoted that would be valid from 2-5mph on flat hard surfaces. From my simple calculation, on a walk that is about 5km long and about 70m altitude, the elevation change is about 6% of the energy and the kinetic energy even less. That seems typical of my walks around town (Bristol, UK).