Manual edit height of track points

Started by insomniux, August 24, 2023, 11:52:23

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insomniux

While manually modifying track points, especially while adding points, the height information of the point seems to be calculated (or ignored). After updating the height information (using the 'Tools/Refresh Elevation'), a good approximation of the elevation is applied to the entire track, but a lot of detail, collected by the GPS, is lost.
Would there be a way to apply the 'Refresh Elevation' tool to just a part of the track, or is there a way to adjust the elevation information of selected point of the track?

Raw data from GPS:
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After applying the Refresh Elevation tool:
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freischneider

What kind of details will be lost ?
Poco F5, Xiaomi Redmi Note 10 Pro, Android 13
Locus Map 4 Gold (always latest version)
LM4 User-ID: 11cec7cb5  (Devices-ID poco F5)
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insomniux

Excuse, the example may not be fully clear but does show the approximation which is applied by the Refresh Elevation tool. Here is another graph where I had to change part of the track. Here is the height information lost after editing. Between 3 and 4km there is a straight line, whereas in reality there should have been a peak up to 560m.

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freischneider

I think you have incorrect offline altitude data.
The best are the lidars from Sony.
Poco F5, Xiaomi Redmi Note 10 Pro, Android 13
Locus Map 4 Gold (always latest version)
LM4 User-ID: 11cec7cb5  (Devices-ID poco F5)
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Graf Geo

#4
I suspect this has nothing to do with "incorrect" offline elevation data.

If I cut out a section in a recorded track with the track editor, for example, it is replaced by a straight line. For this replaced section, a straight line is also generated in the elevation profile between the two end points of the replaced section. Thus, no elevation data is registered in the section itself.

If insomniux uses GPS elevation data during recording, these are stored in the track. If he now changes a section, there can be no GPS altitude data for this area. How could there be, there are no recorded track points in this area. An altitude recalculation will then interpolate or use the offline altitude data, but this only works for the entire track.

@ insomniux: You could try to split the original track, so that the section you want to change is a separate short track. Then make the changes for that one and update the elevation information. Then merge the track parts again (in the correct order:-). The unchanged track parts should then keep the GPS elevation info.

I just tried it with a tack from a hiking guide that contains GPS elevation data and it seems to work that way.

Translated with DeepL. Originaltext auf deutsch:

Ich vermute, das hat nichts mit "falschen" Offline-Höhendaten zu tun.

Wenn ich in einem aufgezeichneten Track mit dem Trackeditor z. B. einen Abschnitt ausschneide, wird dieser durch eine gerade Linie ersetzt. Für diesen ersetzten Abschnitt wird im Höhenprofil ebenfalls eine gerade Linie zwischen den beiden Endpunkten des ersetzten Abschnitts generiert. Im Abschnitt selbst werden also keine Höhendaten registriert.

Wenn insomniux bei der Aufzeichnung GPS Höhendaten verwendet, sind die im Track hinterlegt. Wenn er da nun einen Abschnitt ändert, können für diesen Bereich keine GPS Höhendaten vorliegen. Wie auch, es gibt ja keine aufgezeicheten Trackpunkte in diesem Bereich. Eine Höhen-Neuberechnung wird dann interpolieren bzw. die Offline-Höhendaten verwenden, was aber nur für den gesamten Track geht.

@ insomniux: Du könntest mal versuchen, den Originaltrack zu teilen, so dass der Abschnitt, den du ändern willst, ein eigener kurzer Track ist. Für diesen dann die Änderungen durchführen und die Höheninformationen aktualisieren. Anschließend dann die Trackteile wieder (in der richtigen Reihenfolge:-) zusammenführen. Die unveränderten Trackteile müssten dann die GPS-Höheninfos behalten.

Ich habe es gerade mit einem Tack aus einem Wanderführer, der GPS Höhendaten enthält, ausprobiert und es scheint so zu klappen.

 



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insomniux

Quote from: freischneider on August 24, 2023, 12:36:33I think you have incorrect offline altitude data.
The best are the lidars from Sony.
The altitude data before 3KM and after 4KM is correct. Between those two points the altitude is calculated by the LocusMap app, as those points are manually added (in the app). So my question does not concern the registration of altitude by any device but if there is a possibility (in the app or on the website) to manually correct the altitude of certain points (in this case the calculated points).
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insomniux

Quote from: Graf Geo on August 24, 2023, 13:43:01@ insomniux: You could try to split the original track, so that the section you want to change is a separate short track. Then make the changes for that one and update the elevation information. Then merge the track parts again (in the correct order:-). The unchanged track parts should then keep the GPS elevation info.


That's a good suggestion @Graf Geo, I'll give it a try. I'm however still a bit concerned about the points where the different parts of the track connect after correcting the height data. There may be some jumps which may need manual correction. I've still not figured out how that can be done.
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Menion

Hmm understand, but it is the first time (if remember correctly) that anyone needs a manually modify single trackpoint elevation. In such rare cases, I suggest exporting track to GPX and editing elevation in the generated txt file manually.

Otherwise "Fill elevation" is your best friend. If you require more precise data, consider the suggestion of @freischneider and use more precise elevation data from @Sonny (then that data offered by the app directly).
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insomniux

Yep the most ideal situation would be if the entire track would be recorded with state of the art equipment.

However in this case a part of the track was not recorded at all and was added manually after the track was completed. I also realize that modifying elevation by hand can be an enormous job, especially if the recording trackpoints is dense. For now I'll go for the option to split the track, correct the part which is not correct (using update elevation) and join the tracks together again after the correction. Hopefully at the joining points the difference between the actually measured heights and the heights from the Locus Height map is acceptable.

Thanks for all your help.
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