we've received privately feedback about a potential error in RFC 5870. Could someone who is more familiar with reference systems review Jose's email, and advice whether we'd need to add errata to the RFC?
thanks,
Alex
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Von: José Luis García Balboa [mailto:jlbalboa@ujaen.es]
Gesendet: Dienstag, 24. Mai 2011 13:56
An: christian@spanring.eu; Alexander Mayrhofer
Betreff: altitude in RFC 5870
Dear Alexander and Christian:
I'm reading RFC 5870. Congratulatios for this interesant document
I write to you in relation to the altitude information of the geoURI, because I think there is a mistake.
When using WGS84, the altitude is set in relation to the reference ELLIPSOID (which is the GRS80 ellipsoid), but not to the GEOID.
You can see this, for example, in the definition of the CRS with code EPSG 4979.
In other words, any GPS navigator can offer you the "ellipsoid height " over the GRS80 elllipsoid (there are many ellipsoids), but no any height referred to the geoid (there is only one geoid). This two figures of the earth are completely different.
In page 5 it is said that "altitudes below the WGS-84 reference geoid". This is incorrect. It should say "belo the WGS-84 reference ellipsoid".
In page 10 it is said that "altitudes are relative to the WGS-84 reference geoid rather than Earth's surface". This is also incorrect.
I think this should be correct in a future revision of RFC 5870 (or perhaps any other people has already warned you about this).
Best regards,
**************************************************
José Luis García Balboa
Dpto. Ingeniería Cartográfica, Geodésica y Fotogrametría
Escuela Politécnica Superior. Edf. A-3. Despacho 343.
Campus Las Lagunillas. Universidad de Jaén. 23071 JAÉN (Spain).
Tlf/Fax: (+34) 953 212844 / (+34) 953 212855
Correo electrónico: jlbalboa@ujaen.es
Web: http://coello.ujaen.es
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