Subject: Re: [ids.analysis.forum] DORIS ground marks survey tie
From: "H.Fagard" <[email-masked]>
To: [email-masked]
Cc: [email-masked]
Date: Wed, 21 Feb 2007 14:17:20 +0100

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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