Gps vs Cycle Comp

[Drago]

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

The mileage you've travelled through 3D space, yes. The distance you've travelled along the surface of the Earth, no.

 

[Gatters]

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[/QUOTE]

just as good as it gets like I said earlier, oh I do so hope the OP will be happy and not too worries about any discrepancy caused by a hill

 

[andrew_s]

A perfectly calibrated bike computer will tend to over read the distance, and a perfectly accurate GPS will tend to under read the distance.

The computer works off the front wheel, and the front wheel meanders from side to side as you ride, in order to keep the bike upright, This meandering adds to the ride distance.
The GPS take a position every second and adds up the lengths of the straight line segments between points. However the actual bike track between the points will be a (longer) curve. In addition, as you go round a bend, the bike leans over, and the GPS, up on the handlebars, follows a shorter line on the inside of the wheel track.

 

[raleighnut]

A perfectly calibrated bike computer will tend to over read the distance, and a perfectly accurate GPS will tend to under read the distance.

The computer works off the front wheel, and the front wheel meanders from side to side as you ride, in order to keep the bike upright, This meandering adds to the ride distance.
The GPS take a position every second and adds up the lengths of the straight line segments between points. However the actual bike track between the points will be a (longer) curve. In addition, as you go round a bend, the bike leans over, and the GPS, up on the handlebars, follows a shorter line on the inside of the wheel track.

Aahh but the wheel circumference changes as the tyre leans, it gets smaller too.

 

[Dogtrousers]

Some smartarse is bound to come along soon and point out that due to macro- and microscopic wiggles in the path taken the distance is actually fractal and therefore infinite. Or possibly zero, I can't remember. Or something like that. I saw a program on telly about it once.