Tech help - smart phone altimeters

[MontyVeda]

I've used Strava since it began over here. It's always pinpointed me accurately enough. So I can see which side of the road I'm on etc.
Why would you need to be more accurate than that ?
...

As mentioned in my other thread; regarding cycling along a completely flat canal towpath but the elevation graph is anything but flat because the GPS isn't accurate enough to pinpoint my location on the towpath...

...so the bit where i cross the Lune Aqueduct (in blue) shows my altitude drop from around 25 meters to 5 meters. It thinks I'm fording the river rather than crossing a bridge.

The section between the purple markers on the elevation graph is a five mile section of the Lancaster canal which is dead flat. No bridges, No locks. Just a flat towpath about a foot above the water. Whilst I don't need it to be super accurate, I'd like it to be. I'd like to see a dead flat line on that elevation graph

 

[Ming the Merciless]

As mentioned in my other thread; regarding cycling along a completely flat canal towpath but the elevation graph is anything but flat because the GPS isn't accurate enough to pinpoint my location on the towpath...

View attachment 627412
...so the bit where i cross the Lune Aqueduct (in blue) shows my altitude drop from around 25 meters to 5 meters. It thinks I'm fording the river rather than crossing a bridge.

The section between the purple markers on the elevation graph is a five mile section of the Lancaster canal which is dead flat. No bridges, No locks. Just a flat towpath about a foot above the water. Whilst I don't need it to be super accurate, I'd like it to be. I'd like to see a dead flat line on that elevation graph

What have you plotted that altitude graph in? If it’s Strava itself then it will have corrected the gps elevation data unless your gps also has a barometer built in. You can’t necessarily blame that elevation plot on what the gps recorded. The gps itself has no concept of the aqueduct , it just knows how far it is from a number of gps satellites.

 

[Oldhippy]

Why do you need to know? If your feet are wet you're too low or it's raining and if you're not breathing properly you're too high.

 

[MontyVeda]

Why do you need to know? If your feet are wet you're too low or it's raining and if you're not breathing properly you're too high.

purely academic purposes, if that's OK?

 

[MontyVeda]

What have you plotted that altitude graph in?...

Garmin GPS watch and the Garmin Connect app.

 

[Ming the Merciless]

Garmin GPS watch and the Garmin Connect app.

Check Garmin connect hasn’t made any elevation corrections. Most of them do, if gps doesn’t include barometer or if they don’t recognise it as having one.

 

[Oldhippy]

purely academic purposes, if that's OK?

Of course I just wondered. 😁

 

[cougie uk]

As mentioned in my other thread; regarding cycling along a completely flat canal towpath but the elevation graph is anything but flat because the GPS isn't accurate enough to pinpoint my location on the towpath...

View attachment 627412
...so the bit where i cross the Lune Aqueduct (in blue) shows my altitude drop from around 25 meters to 5 meters. It thinks I'm fording the river rather than crossing a bridge.

The section between the purple markers on the elevation graph is a five mile section of the Lancaster canal which is dead flat. No bridges, No locks. Just a flat towpath about a foot above the water. Whilst I don't need it to be super accurate, I'd like it to be. I'd like to see a dead flat line on that elevation graph

Just mess around with the axes then. I can't see how you can get anything more accurate than that.

If you're going uphills it would show up fine on the graph.
It's just because you're not doing any climbs that the errors on gps show up so much.

If you stretched out the distance or time to more accurately represent the long distance - the altitude would appear flat.

 

[MontyVeda]

...

If you stretched out the distance or time to more accurately represent the long distance - the altitude would appear flat.

If it's not showing flat after five miles, and not showing flat after ten miles, i can't imagine it showing flat on longer distances... why would it?

 

[cougie uk]

https://en.m.wikipedia.org/wiki/Vertical_exaggeration

 

[Alex321]

If it's not showing flat after five miles, and not showing flat after ten miles, i can't imagine it showing flat on longer distances... why would it?

I don't think that is what he meant. He meant stretch out the graph, so that 10 miles (or 32 minutes) covers more than the few inches you have it at.

 

[MontyVeda]

I don't think that is what he meant. He meant stretch out the graph, so that 10 miles (or 32 minutes) covers more than the few inches you have it at.

yet the high points and low points (ignoring the river crossing) still vary between 18m and 27m above sea level, that's 9m or almost 30ft.. a canal with no bridges, no locks, no up and downy bits at all, just a towpath about 12-15" above the water line, really cannot undulate by 30ft.

 

[cougie uk]

yet the high points and low points (ignoring the river crossing) still vary between 18m and 27m above sea level, that's 9m or almost 30ft.. a canal with no bridges, no locks, no up and downy bits at all, just a towpath about 12-15" above the water line, really cannot undulate by 30ft.

It doesn't undulate that much but I don't know of any tech that's more accurate than a Garmin or phone for altitude.

You know it's flattish. Just don't look closely at the graph.

 

[MontyVeda]

According to that - from the web I'm 138 feet and that ties in perfectly with my Strava app.

I'd just use Strava tbh.

So I gave Strava a go. The red line is where Strava thinks i went...

...the dashed yellow line is where i really went.

 

[classic33]

So I gave Strava a go.
The red line is where Strava thinks i went...
View attachment 629100

...the dashed yellow line is where i really went.

Is strava locking onto mobile phone masts?