Went for a ride that included a ten mile stretch along the canal...

[cougie uk]

I've run a 30 mile ultra along the canals from Stratford upon Avon to Bournville. It was all uphill - ok there were locks but why we couldn't run downhill - I dunno.

But yes canals aren't flat.

 

[ColinJ]

I guess I'll have to (one day) get a device with an inbuilt altimeter, to see if i can get a flatline when riding along the Lancaster Canal.

My Edge 500 can gain or lose up to 50+ m on a circular ride (it thinks my doorstep has moved up or down by that much while I was out)!

 

[T4tomo]

so it thinks I'm not on the towpath, but atop a cutting or fording the river.

very much this - I showed my mate the GPS route over the Puig Mayor peak in Mallorca, he expressed concern that the very top was very very steep indeed. It was assuming we scrambled up the hillside, rather than ride through the tunnel.

 

[fossyant]

Hmm, the Peak canal has quite a few locks and bridges, some pretty steep, so my altitude does include climbs etc. The Ashton canal is all down hill into Manchester, again a load of locks to negotiate.

 

[byegad]

...... and now you see the inaccuracy of the American GPS system, it's got better over the last decade, but a 10 meter accuracy (horizontal and vertical) in northern Europe with a good view of the southern sky is as good as you are going to get .

The European Galileo GPS system which goes live in a couple of years will be accurate to within one meter

The US system has a more accurate version, for the military, the civil version is deliberately more fuzzy.

 

[BrumJim]

I've run a 30 mile ultra along the canals from Stratford upon Avon to Bournville. It was all uphill - ok there were locks but why we couldn't run downhill - I dunno.

But yes canals aren't flat.

There's also a monster hill at the Brandwood tunnel near the end.

 

[MontyVeda]

...

But yes canals aren't flat.

This one is... not a single lock for 40 miles between Preston and Tewitfield

 

[Alex321]

Holy thread resurrection!

got a new GPS device and did a 5 mile ride along the canal; no locks, no bridges, just a totally flat canal that can't undulate more than 12" along the stretch I cycled.

Garmin connect screenshot:
View attachment 627339

The canal stretch is between the purple markers on the elevation graph...
Average elevation is around 23m. highest is 27m and lowest is 5m (crossing the aqueduct over the river).

I suppose we can safely assume that @PapaZita above is correct and the GPS data is a few meters off... so it thinks I'm not on the towpath, but atop a cutting or fording the river.

I guess I'll have to (one day) get a device with an inbuilt altimeter, to see if i can get a flatline when riding along the Lancaster Canal.

Which device? Many of them now have a barometer which they use for altitude, rather than using the GPS.

Still not the most accurate thing in the world. My Wahoo has that, and every ride I do which is a loop, it ends up showing a different value for metres gained and metres lost. So my house must have sunk a few metres while I was away

 

[MontyVeda]

Which device? Many of them now have a barometer which they use for altitude, rather than using the GPS.

...

Garmin Forerunner 35... don't think it has an inbuilt barometer.

 

[ColinJ]

Garmin Forerunner 35... don't think it has an inbuilt barometer.

This HAS, for all the good it does!

My Edge 500 can gain or lose up to 50+ m on a circular ride (it thinks my doorstep has moved up or down by that much while I was out)!

My ancient Etrex does better than that without a barometer. It can usually get within about 15 m by GPS signals alone, and nearly always within 25 m.

 

[Alex321]

My Edge 500 can gain or lose up to 50+ m on a circular ride (it thinks my doorstep has moved up or down by that much while I was out)!

My Roam isn't that bad. Rarely more than 10m difference in metres gained/lost, I don't think it has ever been more than 15m out.

 

[ColinJ]

My Roam isn't that bad. Rarely more than 10m difference in metres gained/lost, I don't think it has ever been more than 15m out.

The Edge 500 is pretty ancient - I think it was launched in 2009? 13 years is a LONNNNNNG time for a tech product so I'm not surprised that a modern product is much better.