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Old 02-03-12, 10:48 AM   #1
PerthPete
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GPS vs Sensor for speed

I've just bought the BRYTON Ryder 30, which is a great unit, awesome screen and features.

In the box, it came with 1 sensor and a heart rate monitor, so if you want to track cadence, you are defaulted to use the GPS for speed.

I've always had a magnet sensor telling me my speed, so it feels a little different but have nothing to go from

Has anyone had any experience on the performance and accuracy of the GPS units vs a standard sensor? I'm considering buying another sensor for speed, but it's another $60, so if the GPS is accurate there may not be any need for it.

Thanks in advance.
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Old 02-03-12, 12:26 PM   #2
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I once tested both simultaneously on a ride. The GPS was a Garmin Forerunner and the computer was a cateye. There were some minor differences in speed and distance, but they are so insignificant in my opinion that they don't even merit discussion. I wouldn't hesitate to use GPS. Think about it...No wires to break, No sensors, No wheel size needs to be programmed. It is the ultimate wireless.

The only real issue was reception. In cities with tall building, and I mean a lot of buildings, reception could be lost. Additionally under really, really, heavy tree cover you could also lose the signal. But it was a rare occurrance. This test was in 1997, and I undrstand the antennas in use now are even better.

I still use the forerunner on my Bike Friday. The lack of sensors and wires make packing it up for a trip easy.
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Old 02-03-12, 01:39 PM   #3
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The accuracy of a speedometer/odometer, wired or wireless, which derives its readings from magnetic sensors mounted on fork and wheel should depend upon the circumference of the wheel, which is entered by the user when the unit is installed on the bike.
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Old 02-03-12, 01:47 PM   #4
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Read your instruction manual; the GPS probablyuses the GPS exclusively for location, distance, speed, etc., everything but cadence, and only uses the sensor if the GPS signal is lost. That is they way that the Garmin works. The GPS calibrates the sensor unlike a non-GPS computer where the user does this manually. Your unit may work the same way.
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Old 02-03-12, 02:58 PM   #5
Looigi
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Quote:
Originally Posted by dekindy View Post
...only uses the sensor if the GPS signal is lost. That is they way that the Garmin works. ....
Incorrect. Garmin uses primarily the wheel sensor. You can set the diameter or let it auto calibrate it. If it loses the sensor, it starts using GPS for distance and speed. GPS position is noisy over short distances and clips corners if you ride a tortuous path. That's why they have the wheel sensor.
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Old 02-04-12, 01:48 AM   #6
JimF22003
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I don't bother with the wheel sensor on my Garmins. The gps is plenty good enough.
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Old 02-04-12, 10:24 AM   #7
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Thanks for your feedback guys. I'll stay with the GPS for speed and distance and save the $$. I live in a pretty open city (Perth, Western Australia), so it's all good.

I appreciate your feedback on this.

I took the unit out for a ride yesterday and was very happy with the results. Bryton Rider 30 is looking like a top unit so far. The screen size and customisation on what is where is awesome.

I use the cadence sensor and it's proving to be a big help to push me a little harder.
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