Gps vs Cycle Comp

[grellboy]

Morning. Was given a Giant Axact Cycle Computer the other day and after finally getting it to wirelessly sync with the magnet I went out and did 31.31 km this morning at 25.5 kph.....or was it 30.6 km at 24.9 kph!? The first figures are from the bike computer, the second figures from GPS on my phone app. Which is likely to be more accurate?

 

[T.M.H.N.E.T]

A little from column A and a little from column B.

 

[Gatters]

GPS will be accurate, I set mine up so the cycle comp is dead on in agreement with gps

 

[grellboy]

GPS will be accurate, I set mine up so the cycle comp is dead on in agreement with gps

I thought about doing that and am now trying to work out whether to increase or decrease the tyre size figure (circumference?) to make the computer tally with the gps app lol!

 

[raleighnut]

If the bike computer says more miles and faster then the wheel is spinning more so decreasing the circumference will bring them into line, however does the gps take hills into account for distance (if you are going either up or down the distance is further than a gps will register)

 

[Big Dave laaa]

Just use it as a guide it's irrelevant really. If I go out in a group ride, when we all upload to strava it's always weird to see the differences in speed, average speed and elevation between the riders. I just keep a bike log spreadsheet to monitor my progress over the year. If the trend lines go the right way I'm happy

 

[Yellow Saddle]

Confucius says man with two watches never know time.

Although the issue can be rectified as Raleighnut explained, it is not important that you know the exact distance. It is just a number. Your bathroom scale and the gym scale never agrees either, but if you just rely on one scale you know if you've put on weight or not. If I have to sit through one more club ride post-mortem where the actual distance of the ride is debated, I think I'll just yawn loudly, look at my watch and start clipping my toe nails.

Ride, drink a beer, laugh and get on with it.

 

[contadino]

Endomondo often tells me I've climbed further than I've descended which, on a circuit, would be worrying.

 

[Dogtrousers]

The one that gives the most impressive results is right. In this case the computer results are both further and faster. So it's doubly right.

 

[xxDarkRiderxx]

The one that gives the most impressive results is right.

I agree to many numbers to think about. I might remove my polar cycle computer and just use the Polar GPS watch and Garmin. And all that uploading to Polar Garmin and Strava is doing my head in.

 

[Big Dave laaa]

I never ever ever click elevation correction on Strava only did that once!

 

[Drago]

GPS will be accurate, I set mine up so the cycle comp is dead on in agreement with gps

Not automatically it won't. The Speedo will be measuring speed along a constantly undulating surface, whereas the GPS is measuring speed through constantly recalculated points in 3D space. The the reason the results differ - assuming both are operating accurately - is because they're measuring 2 different things.

 

[Gatters]

Not automatically it won't. The Speedo will be measuring speed along a constantly undulating surface, whereas the GPS is measuring speed through constantly recalculated points in 3D space. The the reason the results differ - assuming both are operating accurately - is because they're measuring 2 different things.

I didn't say the process was automatic in any way, in fact it is a very manual task.

What I was trying to say is this

If you do a certain mileage you assume that the stated mileage shown on the gps is accurate...yes?

then if the magnetic impulse cycle computer shows a different mileage, change the setting of the wheel circumference and try again next time...do this as many times as is necessary to achieve accuracy and agreement between the two...That's about as good as it gets

 

[raleighnut]

I didn't say the process was automatic in any way, in fact it is a very manual task.

What I was trying to say is this

If you do a certain mileage you assume that the stated mileage shown on the gps is accurate...yes?

then if the magnetic impulse cycle computer shows a different mileage, change the setting of the wheel circumference and try again next time...do this as many times as is necessary to achieve accuracy and agreement between the two...That's about as good as it gets

Yeah but if you ride a flat straightish 10 mile route they will read differently to a hilly 10 mile one with bends in it due to how they work.

 

[Gatters]

I thought about doing that and am now trying to work out whether to increase or decrease the tyre size figure (circumference?) to make the computer tally with the gps app lol!

if your magnetic pulse computer shows more miles than the gps...reduce the wheel circumference by 10mm...when you get close you can trim i

Yeah but if you ride a flat straightish 10 mile route they will read differently to a hilly 10 mile one with bends in it due to how they work.

tell you what..set the fecker up on a flat route and have done with it