Message-Id: <6.1.1.1.2.20070221165902.02276130@pop.cls.fr>
Date: Wed, 21 Feb 2007 18:43:40 +0100
To: ids.analysis.forum@cls.fr
From: Laurent Soudarin <laurent.soudarin@cls.fr>
Subject: Re: [ids.analysis.forum] DORIS ground marks survey tie
In-Reply-To: <a06240822c201f26abcff@[172.16.0.131]>
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Dear all,

Richard Biancale and I would rather keep the tie information in the sitelogs.
The ground mark is the only one to be really perennial. It will allow to 
measure ground motion
over several decades, even without DORIS.
That is why the tie information must be easily accessible to the users. 
Moreover, the tie must be kept available
if, one day, it was finally decided to adopt the ground mark as the 
reference point.

Best regards
Laurent


Le 14:17 21/02/2007,H.Fagard écrit:
>Dear Zinovy, dear all,
>
>At 13:05 +0300 21/02/07, Zinovy Malkin wrote:
>>Usually, e.g. for SLR and GPS we prefer to refer the
>>computed coordinates to the ground mark
>
>Yes this is the "normal" and much better convention. Unfortunately this 
>was not initially chosen for DORIS, and we have to live with that. 
>Moreover, the chosen "DORIS reference point" (i.e. the point whose 
>coordinates are published) for the second generation antennas (Starec 
>type) was not a good choice either: it is neither the point on which 
>positioning measurements are actually carried out (the 2 GHz phase 
>centre), nor the easiest one to accurately survey (the base of the 
>antenna). Therefore we (at IGN) need to take special precautions when 
>installing and surveying such antennas, in order to take into account 
>geometry defects of the antennas (which were noticed at several sites).
>
>Best regards,
>
>Hervé
>
>
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