[Proj] Geodesic distances away from the ellipsoid

OvV_HN ovv at hetnet.nl
Fri Mar 20 13:49:55 EST 2009

----- Original Message ----- 
From: "Gerald I. Evenden" <geraldi.evenden at gmail.com>
To: <proj at lists.maptools.org>
Sent: Friday, March 20, 2009 6:24 PM
Subject: Re: [Proj] Geodesic distances away from the ellipsoid

> There is also the 3D geodesic at the NGS site which might apply and give a
> better answer.  But I think the above would be good enough for most 
> purposes.
> Try both and see what happens.
> PS: I did not convert the NGS 3D because it was hard-wired for WGS84 and 
> the
> description was confusing enough that I decided against bothering for the
> time being.  Also, I could not get a mental image of what was happening 
> when
> there was a difference of altitude at the two end points.

The last time I looked at the code the geodesic was calculated for an 
altitude of 0 meters above the ellipsoid, all the way. I forgot where the 3D 
information was used for, probably the chord distance or the north-east-up 
coordinate difference.

Oscar van Vlijmen

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