Hi There,

I've come across some mixed documentation and wanted to check with the community regarding standards.

OSM defines the "ele" tag as elevation above mean sea level.
This other OSM wiki page that defines "Altitude" mentions the use of the WGS84 Ellipsoid.
Also, the GPX 1.1 Standard uses WGS84 heights for its "ele" tags.

Based on the above information, are the following assumptions correct?

  • Any "ele" tags in OSM are MSL (mean sea level) heights in meters.
  • Any "ele" tags in GPX files are WGS84 heights in meters.
  • GPX files also contain and optional "geoidheight" tag that describes the undulation in meters at that point.

I'm trying to sort this out to ensure the height information in the GPX files that I upload are correct.
Also, is the "ele" tag even used much in OSM? do most editors ignore/avoid it?

asked 27 Jan, 16:06

Ian%20Colwell's gravatar image

Ian Colwell
11112
accept rate: 0%


Hi.

I use ele only if it's written on site. On a sign or some kind of marker.

GPS altitude is usually most unreliable (to be polite), except if you have dedicated hardware.

And data consumers usually use SRTM or suchlike to have global coverage.

The "Altitude" page you refer to seems deprecated : "there was also a proposal (on this page) to use Key:alt for this purpose. This was never explained properly. Please see ele=*".

Hope this helps.

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answered 28 Jan, 02:00

H_mlet's gravatar image

H_mlet
1.7k732
accept rate: 13%

Thanks! I'll assume my 3 assumptions are correct then.

(28 Jan, 15:28) Ian Colwell
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question asked: 27 Jan, 16:06

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