Tech help - smart phone altimeters

[Ming the Merciless]

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?

Scales, the graph isn’t to scale with the y axis exaggerated relative to x. Stretch out x appropriately, so it is to scale, and you’ll get a true view.

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.

That shows a very low resolution track. Not one a working gps would provide.

 

[Ming the Merciless]

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.

Calibrated altimeter over short timescales where weather doesn't significantly change is more accurate.

 

[cougie uk]

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.

That's a very poor Strava track. By comparison I use Strava on my phone to track my dog walks and it's spot on down to whxih side of the road I'm on.
Check your settings on the app ? That area looks pretty open to the skies.

Settings > Additional Settings > Battery & performance > Manage apps battery usage > apps > Strava. Settings > Additional Settings > Privacy > Location > ensure you are using High Accuracy for Location Mode and allowing location access.

 

[MontyVeda]

Is strava locking onto mobile phone masts?

that could explain the two 'jumps' over the river as there's a couple of masts over there... but elsewhere on the journey it went completely off piste, where there aren't any masts (to my knowledge).

 

[MontyVeda]

That's a very poor Strava track. By comparison I use Strava on my phone to track my dog walks and it's spot on down to whxih side of the road I'm on.
Check your settings on the app ? That area looks pretty open to the skies.

Settings > Additional Settings > Battery & performance > Manage apps battery usage > apps > Strava. Settings > Additional Settings > Privacy > Location > ensure you are using High Accuracy for Location Mode and allowing location access.

some sections; 1st half mile and last mile were bob on... just a few sections like those in the image where it went skipping all over the place.

Can't find any of those settings on my phone, but the settings i can find it looks like it set to be more accurate than less accurate.

 

[MontyVeda]

Scales, the graph isn’t to scale with the y axis exaggerated relative to x. Stretch out x appropriately, so it is to scale, and you’ll get a true view.

...

It doesn't matter how far i stretch out the elevation graph... the graph may appear flatter to the eye, but the elevation data still claims that the flat towpath varies up to 30ft.

 

[Ming the Merciless]

It doesn't matter how far i stretch out the elevation graph... the graph may appear flatter to the eye, but the elevation data still claims that the flat towpath varies up to 30ft.

Maybe so, but the track you have published is such a rough low resolution thing that the gps clearly didn’t have a proper lock on satellites. Your first task is to resolve why that’s the case, if you are to resolve your issue.

 

[Alex321]

It doesn't matter how far i stretch out the elevation graph... the graph may appear flatter to the eye, but the elevation data still claims that the flat towpath varies up to 30ft.

Yes, but the track it shows doesn't follow the towpath - the horizontal track is off by way more than the vertical. And by going so far off the real path, it was probably hitting places with different elevation.

 

[MontyVeda]

Yes, but the track it shows doesn't follow the towpath - the horizontal track is off by way more than the vertical. And by going so far off the real path, it was probably hitting places with different elevation.

yes. hence my quest for something a bit more reliable

one poster suggested Strava, tried that and got this...

I'm not even gonna bother checking it for elevation accuracy

 

[Alex321]

yes. hence my quest for something a bit more reliable

one poster suggested Strava, tried that and got this...
View attachment 629143
I'm not even gonna bother checking it for elevation accuracy

That was the track I was referring to. Strava just goes from the information your phone gives it.

The issue is with your phone GPS values. It looks like your phone is not getting a GPS signal (for that section), so for location it is going by the cellphone towers.

 

[DaveReading]

And by going so far off the real path, it was probably hitting places with different elevation.

Pardon my ignorance about these things, but does Strava actually use a digital terrain model (elevation vs location) ?

 

[Ming the Merciless]

Pardon my ignorance about these things, but does Strava actually use a digital terrain model (elevation vs location) ?

Yes, unless the source gps is recognised as having a barometric altimeter, in which case it will use the values from the GPS. In this case it will be using DEM, but the gps fix of the OP is so shoot anyway I’m not surprised the elevation data is crock. As per other posters I suspect it doesn’t have a gpx fix at all, but is using cell phone mast data for location.

 

[MontyVeda]

I'm gonna try a similar ride again later today, this time with the Strava and Garmin linked... see if that makes any difference

 

[cougie uk]

Do you let your Garmin and phone get a good lock before starting recording ?
And my phone is just in my pocket but always has a good track. It might not if it was packed away more ?

 

[MontyVeda]

They lock to the GPS before i start moving, yes.

Just linked my Strava and Garmin connect account together...

Yesterday, the section over the river with strava on its own was skipping all over the place, and the Garmin watch had my position correct but the elevation completely wrong... combine the two and hey presto.

consistent 72ft elevation all the way along the towpath and 73ft on the aqueduct itself, seems about bang on now