Comparing power readings from PowerCal and PowerTap
This weekend I wrote about the first ride PowerCal (see here).
Now, I have more data about these rides.
I did 4 rides of varying distances, on two different bikes, each with different profiles, and I compared the power readings by capturing them on two separate Garmin units pictured above.
On this weekend’s post, I made a numerical comparison between the rides, by comparing the power average, normalized power and TSS calculation… This time, I’m focusing on pattern comparison.
The objective was to identify the power pattern exhibited by PowerCal and PowerTap, and watch the differences.
Here are the results, PowerCal in red, PowerTap in blue:
The first and most obvious result is that the PowerCal power reading does indeed match very well with the Power reading from the PowerTap.
A very small lag can be observed, as well as the fact that the PowerCal power reading tends to be smoother than the reading from PowerTap.
The is also the obvious fact that PowerCal tends to show a power reading, even when there is coasting (going downhill). This is more obvious on the second and third graph as in the others there weren’t any significant downhill/coasting periods.
Notice how the red line (PowerCal) is above zero, when the blue line is pegged at zero. This is a downhill section where I was coasting. Other sectors where there is a downhill but I kept pedaling do not display this pattern. One incentive for you not to stop pedaling on the downhill !!!!
The table below compares the 4 rides, as measured by the two Garmin device, for each the PowerTap numbers of the first line, then second line the PowerCal numbers.
|distance (km)||climbed (m)||duration||kph||bpm||Avg Power||NormPower||TSS|
|Ride 1 = 82.03||585||3:17:28||24.93||144||182||203||233|
|Ride 1 = 82.24||586||3:31:31||23.33||144||167||198||219|
|Ride 2 = 37.12||373||1:42:32||21.72||136||193||215||126|
|Ride 2 = 37.26||397||1:43:51||21.53||136||173||190||100|
|Ride 3 = 44.35||692||2:08:46||20.67||144||190||227||176|
|Ride 3 = 44.71||551||2:13:53||20.04||144||194||217||169|
|Ride 4 = 49.00||171||1:51:06||26.46||141||187||206||126|
|Ride 4 = 48.97||192||1:51:02||26.46||141||179||190||107|
There is a tendency for PowerCal to be on the conservative side when compared to the actual power number from PowerTap, except for ride#3, which had several pronounced segments of downhill/coasting.
This table shows a remarkable accuracy for PowerCal, a device that derives power from heart rate, using statistical methods alone. The algorithm created by CycleOps is truly spectacular achieving very impressive numbers and showing that a very simple device can achieve impressive results !!!!