Wrong altitude in the recording

Aldo Viano shared this problem 3 months ago
Solved

It is impossible to do more than 4000 meters with 12,8 km in 2.46 hours. What 'wrong? See attached screenshot

Replies (12)

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How does the graph look like? Must have tons of"virtual" ups and downs, right?

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Yes, it Is. See attached screenshot. I have seen other similar topics and have set accordingly. This morning, another walk, same story.

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There are these breakdowns of elevation visible down to 100m. I would look at the NMEA data in /data/nmea folder of Locus.

I cannot imagine Locus is hallucinating here, but rather processes what the device sensor delivers via Android.

In any case the NMEA data is needed to understand first of all. You have to activate this logging in the settings (just search for nmea)

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Already done yesterday. Today nothing changed. Now I have switched on "always".

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Hi, I have activated NMEA in settings. No change today. Better than before, but still wrong height difference. See attached. I wonder why at the beginning, when I did install the app, everything was working good...

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NMEA is meant to allow to look at what Android delivers to Locus. So you can look at the respective time and check. Wikipedia will tell you the format of the NMEA string.

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In addition, here is Michal's advise from a similar case:

Please get Locus Map permission for all-time access to the location and exclude Locus from all means of battery optimization so that the app can run in the background, see http://docs.locusmap.eu/doku.php?id=manual:faq:gps_lost_fix_android6. Also, try switching on or off Google Services assisted location in Locus settings - GPS&sensors.

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Hi,

When I install an app, I am not supposed to look at Wikipedia nor to know some tricks to let the app work correctly. The app should work, that's all. If not, I simply look for a different app.

I have uninstalled, then installed again th app on my Android smartphone.

I have done a short test this morning leaving the settings as they are. And it works! I hope it will work well again longtime.

Regards

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Not sorry to contradict, Aldo.

Reality is, that there is a potentially complex interference between the different layers of the hardware and software architecture of the beast that you hold in your hands so smoothly. In most cases you are right in the assumption and wish to be ignorant of above and just enjoy an app. When it comes to geo apps, people may experience a hard fall. When you look around in the web in the right forums you'll even find cases where Google Maps looses GPS location. Especially with device vendors that employ a rude "battery saving" policy in their Android flavor (in the past Huawei was most infamous - they even killed apps that when they ran as a service and were exempt from any "savings".

But you are happy to see it just work now and can forget about digging for details in log files. Enjoy :-)

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I honestly don't know what to think of this app anymore. I uninstalled it, reinstalled it, it worked fine without changing the settings. Then, it made absurd height differences again. I adjusted the settings according to your instructions. Always a shocking graph with the differences in height. I installed another app... which I'm not happy with. After returning from my hike today, I tried to record a track while driving. And… this time it worked well. But how can I trust an app that works every other time? Help!

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Elevation data from GPS reception is too variable, inaccurate and thus (imo) unusable to make sense. I ride in fairly flat terrain but when I look at the elevation graphs it sometimes seems as if I had been somewhere else entirely. Locus only reports the data provided by the GPS receiver. Locus however does offer you the possibility to replace the received elevation gps nonsense with some better elevation data. You notice in the images the original gps result and then after the elevation data update.

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The version after the altitude update is already more in line with reality. Even if you use this data to calculate details such as altimeters using different tools, you won't get much use out of it. Most calculation methods give a totally false picture of reality. If I walk up the stairs at home I already have more altimeters than if I cycle 20 km here. Statistics by GPS altitude is nonsense as far as I'm concerned or at least is to be taken with a very large grain of salt (a big bag of salt).

But if you still have the necessary courage to experiment. Locus sure offers you some optimisation options.

Find out here. And anyway, keep enjoying your walks through mountain and valleys.

https://docs.locusmap.app/doku.php?id=manual:user_guide:tools:altitude&s[]=elevation

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Still this.

> I tried to record a track while driving. And... this time it worked well.

When cycling you have fewer problems ?
Where do you put your phone when cycling ?
Where do you put your phone when walking ?
An unobstructed sky view is definitely optimal.

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Your device has a problem. There are two ways out: 1) dig deeper in root cause analysis (not your preferred way I understood from your earlier post) 2) download Sonny's elevation data 1", mostly LIDAR for Europe, then instruct the Locus Altitude Manager to use those data instead of GPS.

That will fix your vertical dropouts. If there should be horizontal GPS gaps, option 1 is the only way.

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I also use the lidar data from Sonny. If the weather is stable, you can also use a barometer. Some phones have this built in. You can set it up in the Locus altitude manager.
In some cases this can even be an advantage.

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Maybe I found a solution, simpler than I thought. But maybe it's because I don't know all the functions of the app yet. This morning I did two short tests. The first, as always, showed a graph with absurd height differences (more than 4000 meters in a few kilometers). The second one, done while driving the car, seemed more reliable. After saving the tracks, I clicked on the options (three overlapping dots, bottom right) and the "update altimetry" function appeared (I'm not sure if it gives the exact wording in the English menu). The graph is "optimized" by showing a total height difference in line with the altitudes detected manually on the map.

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Hello,

yes, this could be the solution for already recorded routes. For the new recordings you can achieve the same result if you use SRTM data instead of recorded ones.

Here are some recommendations for the altitude fix:


Open Locus settings > GPS&sensors:

  • Location filter > select medium or heavier filter
  • Google Services assisted location > turn it ON
  • Altitude manager > settings tab > SRTM data - select "Optimize GPS values" or "Replace GPS values"
  • Altitude manager > settings tab > Pressure sensor > turn ON (if available)
  • Altitude manager > settings tab > Altitude filter - select medium or heavier filter

More here: https://docs.locusmap.app/doku.php?id=manual:faq:wrong_gps_data#custom_altitude_threshold


Zdenek, Locus team

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Hi Zdenek.

If possible improve gps elevation records would be optimal.

Anyway so I haven't tested heavy filtering (LM3) anymore.

Elevation update indeed works but it remains a workaround.

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0m altitude belongs to a passage through an old riverbed.

Track record original. LM4 only tolerance glider ? (LM3 user)
I suppose does eliminate the smaller elevation trkpt variations ?
However, in the Aldo Viano records you see BIG elevation glitches.
As reported by Michael, there is something more serious going on.
In the graph you notice a surely deadly acceleration (free fall).
Can Locus (NMEA) detect such and eliminate this by a bypass ?
Compare with.
By total gps lock loss you create trkseg's and a distance bridge.

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Above all, don't let all those statistics and numbers spoil your GPS experience.

The following link tells more. Notice: The vertical accuracy is simply not very good.

https://www.gpsvisualizer.com/tutorials/elevation_gain.html

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Hi 0709,

Ok, let's assume that vertical accuracy is not very good. However, what is "good enough"?

If I'am hiking for 15 km where the altitude should be, let's say, 1000 meters, and at the end of the day the app shows 1010 meters, that's fine, really it doesn't matter. If it shows 4987 meters... would you agree that the GPS experience is below zero? 🤣

In 2023 I have recorded 25 hikes, about 370 km and 25.000 meters positive in total. If the altitude sum was 25.103 instead, I would even sleep at night like a baby.

On the contrary, if it was three times, ok, I would look for another app. Or no app at all.

Bad weather today and for the weekend. I will test again next week and will let you know the issues.

Forgive me for my bad English

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Aldo, if the sensor delivers crap, no app on this planet - also beyond- can hide that.

You got tons of advise how to avoid the unacceptable end effect of above. Either play with optimization and filtering, or just use the LIDAR data that is available. At recording time. Then you will never see the GPS sensor crap.

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Maybe your sensor is broken. Then you need a new phone. Or they do it with the lidar data.

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Michael,

I thank anyone have posted some suggestions on this matter. I'm keeping trying and I will do some more tests as soon as I can. However, I'm quite sure that I have found a good compromise (see one of my previous post) adjusting the height difference "after" recording it, with the option that I didn't notice before.

Again, thank you for your help. I will let you know.

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Hi Aldo.

Rain? Here also (too) MUCH rain.

- Those big elevation glitches cause should be found and solved.
Test with another phone and make sure you have free sky view.


- Elevation accuracy.
The more mountain and valley, the less the small elevation jumps interfere.
On flat terrain you notice this because of the limited altitude display range.


- In attachment a Locus track record which does suffice for me.
I usually only look at this once to share. The accompanying figures?
Every tool calculates differently. I mainly remember the nice trip.


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Hi everybody.

Sunny morning today, I did my usual training walk. In attachment, see the screenshot of my tracking. Originally the height difference was more than 2000 meters during 10 km walking, but I used the option "adjust altitude" and finally the result was reasonable (see my previous posts). I don't care if it is 100% accurate, it seems good enough.

This solution is suitable for me.

I hope this will help anyone having the same problem.

Thanks a lot for you support.

Il 6 gen 2024 10:05, Locus Map <locus.map@asamm.com> ha scritto:

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