Altitude erreur

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GOUPIL 30101

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Jun 27, 2021, 9:09:30 AMJun 27
to OsmAnd
Bonjour, avez-vous aussi observé des erreurs d'altitude de l'ordre de 40 à 50 mètres en plus de l'altitude réelle ? Avez-vous réussi à corriger cela ? Cordialement.

Hello, have you also observed altitude errors of the order of 40 to 50 meters in addition to the actual altitude? Did you manage to correct this? Cordially.

Poutnik Fornntp

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Jun 27, 2021, 10:09:50 AMJun 27
to osm...@googlegroups.com, GOUPIL 30101
It may be related to if there is applied an automatic or manual correction of GPS WGS84 geoid altitude to Earth "potatoid".  

Without correction, GPS gives for middle Europe about 60m higher altitude than kartigraphic altitude.

Most Of better application offer such correction, or do it implicitly. Check the GOD settings.

Dne 27. června 2021 15:09:36 GOUPIL 30101 <goupi...@gmail.com> napsal:

Bonjour, avez-vous aussi observé des erreurs d'altitude de l'ordre de 40 à 50 mètres en plus de l'altitude réelle ? Avez-vous réussi à corriger cela ? Cordialement.

Hello, have you also observed altitude errors of the order of 40 to 50 meters in addition to the actual altitude? Did you manage to correct this? Cordially.

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Greg Troxel

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Jun 27, 2021, 10:11:56 AMJun 27
to GOUPIL 30101, OsmAnd

GOUPIL 30101 <goupi...@gmail.com> writes:

> Hello, have you also observed altitude errors of the order of 40 to 50
> meters in addition to the actual altitude? Did you manage to correct this?
> Cordially.

This is complicated:

The android location API returns "height above ellipsoid (HAE)" which
is not what people call altitude.

osmand is just a client using your phone's GPS (GNSS) receiver.
First figure out if the phone is ok. Install GPSTest which will show
"Height Above Ellipsoid" labeled, somewhat confusing, as "Alt", and
"WGS84 Orthometric Height", which is very close to what people mean by
altitude as "Alt (MSL)". You will notice that they are different.

To look up the difference between HAE and WGS84 Orthometric Height,
see
https://geographiclib.sourceforge.io/cgi-bin/GeoidEval

osmand has a downloadable map called world altitude correction.
Without it, osmand displays HAE, and with it, WGS84 Orthometric
Height, which is effectively a global definition of altitude.
Make sure you have this installed.

You would be correct to say that this is all unfortunate. That the
complexity exists is unavoidable, but that you are having to deal with
it is because of the choices made in writing the Android API.
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GOUPIL 30101

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Jun 28, 2021, 5:12:03 PMJun 28
to OsmAnd
J'ai effectivement téléchargé le fichiers des altitudes, il semble que l'écart d'altitude s'est très sérieusement réduit et qu'il soit maintenant très proche de la réalité. Merci.

I did download the elevation file, it looks like the elevation gap has narrowed very seriously and is now very close to reality. Thank you.

Dmitry Prodchenko

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Jun 29, 2021, 5:58:48 AMJun 29
to OsmAnd
Hello! Thank you for the feedback.
You need to download the "World altitude correction" map from Menu – Downloads – World maps.

Greg Troxel

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Jun 29, 2021, 8:30:04 AMJun 29
to Dmitry Prodchenko, OsmAnd

Dmitry Prodchenko <dmpr...@gmail.com> writes:

> Hello! Thank you for the feedback.
> You need to download the "World altitude correction" map from Menu –
> Downloads – World maps.

It would be really nie if somehow the icon/text were differetn so that
without the correction file loaded one would see the logical equivalent
of "HAE (Height Above Ellipsoid)" rather than "Altitude".

Maybe change theicon from mountain to an arc with a perpendicular?
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