External accelerometer - Dual or Garmin?

Discussion related to external and internal GPS / GLONASS / Galileo / BeiDou sensors
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Funduro
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External accelerometer - Dual or Garmin?

Post by Funduro »

First post so please be gentle...

I ended up here after watching this Fortnine youtube video in which Harry's Lap Timer is used in conjunction with the Dual external sensor to record his friction circle/g-g chart

https://youtu.be/LW6lMIdy73k

Clearly there's no need for me to want to do this with my road bike, but that doesn't mean that I don't want to! As I like to keep my phone safely tucked away, I wanted to use an external sensor that I could tape to the bike, but because of the cost/availability of the Dual, I've opted for the Garmin GLO 2.

It's all up and working, but I note that while I'm getting the GPS signal from the Garmin, it's still the (Android) phone's internal accelerometer that's being used.

Does the Dual have an accelerometer that the Garmin doesn't (so I bought the wrong product), or does Lap Timer derive the cornering forces from the GPS signal so where the accelerometer signal is coming from is irrelevant (so the Garmin is fine)?
Funduro
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Re: External accelerometer - Dual or Garmin?

Post by Funduro »

As I'm still not sure, I've bought a used Dual 150 from eBay so I'll have both to play with and see what happens
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Harry
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Re: External accelerometer - Dual or Garmin?

Post by Harry »

Hello,

Even in case a GPS, OBD, video sensor connected provides an IMU (including acceleration sensor), LapTimer doesn't use it. Transferring IMU data at rate of 20 to 100Hz simply wastes too much bandwidth and doesn't add a benefit. Furthermore, the problem with motorbikes is, that lateral acceleration is zero-ed when it is mounted with a constant angle to the motorbike body. So LapTimer has a predefined mounting position for motorbikes allowing the calculation of lateral acceleration (and lean) from downforce. That's working good enough for most. In case acceleration doesn't look good, you can always calculate it from GPS by selecting a lap in Lap List, follow Fixes ‣ second icon in the bottom and trigger calculation of acceleration from GPS.

So everything's fine with your GPS device.

- Harry
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