Cadence data from Speed Sensor and wireless derailleur

Does Wahoo Bolt v2 require Cadence sensor to collect Cadence data when it is connected to Speed Sensor and wireless derailleur (Sram AXS)?

Speed Sensor detects wheel diameter (and allows to manually configure wheel/tire size).
Wireless derailleur provides live feed of selected gear (and it is possible to specify in menu gear range/sprocket size).

I ask because I realized that current speed, wheel diameter, and selected gear is all the data needed to calculate cadence, so if it is possible to collect cadence data without sticking/strapping some blinking gizmo to my crank/shoe I would like to avoid it.

It will not calculate cadence on its own. That information would be insufficient to do so with any kind of vague reliability. Cadence is the rotation of your pedals. Using the information you’ve stated would be rotation of the wheels, which is not the same thing.

Oh, and even factoring in the current gear you’re in I don’t think it’d be good enough. Any coasting and it’d definitely be wrong.

Has there been work done with any other solutions for deriving cadence from such information?

Lol, I completely forgot about coasting.
My solution would be “a cadence assuming you are pedaling at all”, but ignoring this obvious flaw it could be reasonably accurate even if tire pressure affects effective wheel diameter (for sure better accuracy than single band GPS of my Bolt reporting 80kph max speed in forest fire road). I wonder how Wahoo sensors reports speed and cadence. If smallest data points corresponds to single rotation, than Speed Sensor provides finer granularity as in majority of cases wheels rotates faster than cranks.
Still, not the greatest idea.

Out of curiosity I checked specs of Bolt and Roam.
The latter one besides of dual band GPS also has an accelerometer and gyroscope.
Pedaling probably always causes some detectable wiggling of bicycle. I wonder if they could implement cadence feature which would report calculated cadence only if accelerometer detects wiggling with frequency matching expected cadence.

I think with the normal road buzz, small flex on mounts etc it would be next to impossible for it to de-noise the signals enough to isolate a pedal stroke. I’ve idea though!

GPS isn’t sensitive enough to determine if your bicycle were moving side to side. Current iterations are accurate while moving down to 3 meters/10 feet.

Smart trainers can sense cadence as torque pulses for each pedal stroke. It works pretty well as long as two distinct power pulses are detectable. It has trouble with low power spinning, particularly at high rpm, or with pedaling irregularities. Of course crank and pedal base power meters must directly measure crank rotation in order to determine power, so also read out accurate rpm. I’m using a $17 Magene sensor that can be configured to read cadence when attached to a crank or speed when attached to a hub.

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