Re: TLE (was Geodetic) precision

From: Bjoern Gimle (
Date: Mon Aug 20 2001 - 21:35:51 PDT

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    Though I am not an expert, I'd like to comment on this:
    > Are you suggesting that SpaceCom somehow deliberately degrades the orbital
    > parameters of satellites such as NavStar and Transit to no better than 500
    > metres?  If so, it seems a rather pointless degradation as it is so easily
    > corrected by the user community.  The IGEX programme for example, tracks
    > Glonass and NavStar (and occasionally a few other) satellites to an
    accuracy of
    > well under five metres and cumulatively to sub-metric precision, albeit in
    > relation to the rather wacky PZ-90 datum.
    No, there are three different issues here. The NavStars "know" their
    position, and include that information in their broadcast. Standard elsets
    can be osculating, and very accurate for a short period; or average, and
    "doctored" to fit the SGP4 prediction model, which has large imperfections.
    > I think it was Albert Einstein who once said that:
    > The Truth ought to be expressed as simply as possible, but never more so.
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