The first number “Tbp” is the number of minutes it would take you to cycle that course if it were tarmac'ed, on a good road bike, if you weighed 72kg, if your bike is 8kg and if you are able to keep generating a constant 200W (a well trained cyclist) - this can be considered a measure of "length adjusted for hilliness"
The second number named Hardness is the "average hilliness" measure - with 100 being flat, 50 being mostly downhill, 200 containing lots of uphill - note that a course that is equally uphill and downhill will still score higher than 100 as you lose more going up than you gain coming down.
The third number, Sti, is simply TBP noted as a time (in hours)
The final number is the average speed that would be achieved by the imaginary 200Watt cyclist.
Some examples:
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Climb of Alpe d’Huez
Dist: 14km
Ele: 1104/0 m
Tbp: 90 Hardness:379
Sti: 1:29 (9.1 kmh)
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Biking around in flat Holland
Dist: 51km
Ele: 0/0 m
Tbp: 90 Hardness:101
Sti: 1:30 (33.9 kmh)
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These 2 very different exercises have, according to Runsaturday-Tbp, the same toughness:
- The first is a 13 km climb starting from 721 meters and climbing to 1841m above sea-level scaling Alpe d’Huez in France. The 13km will take you (72+8kg and 200Watt) 1:29 hours with an average speed of 9,1 kmh.
- The second is 51 km in flatland Northern-Holland (the lowest point is -4 meters, the highest point 1 meter above sea level) - it will also take you 1:30 hours.
So while totally different in length and profile, both rides can be roughly compared in toughness.
TBP is approximate
It relies on the quality of the data going in. It's also much more sensitive on raw GPS run data, than it is on the mapper generated map data. This is simply because there are many more readings and there is much more "noise" in raw GPS data. If you run exactly the same course twice, then please don't expect the same TBP scores twice - although hopefully they will be similar.
Also, please remember that you are not the hypothetical cyclist - a person who's heavier than 72+8kg will relatively need more power to climb than a lighter person. Also factors like wind, rain, tyres, aerodynamics, and road-surface all have an important impact on real performance.
Final question
What does TBP mean?
....I invite people to guess :)