Re: Geodetic precision - food for thinking

From: Joerg Kampmann (
Date: Thu Aug 16 2001 - 14:55:52 PDT

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    hi, this is really very interesting. e.g. when I quote my position I am
    referring to :-)
    and I do not know the geoid they are using. our local maps say I am 60 m
    above sea level ...
    now: as you say the same location differs about 124 m according to
    different géoids.
    I am asking: what precision do we actually need here ? for the normal
    observer - like me an "aficionado" - I think I do not really need the
    referring geoid ...
    but that may not be the case in every instance. But then we have some
    real problems: 
    - the elsets what geoid do they require?
    - how can we transform - in case we need that precision - data from one
    geoid to the other in order to make data comparable ?
    just food for thinking
    Allen Thomson schrieb:
    > > As a newcomer to the List, from the background of being a Geodesist,
    > > I've been wondering about the apparent precision of some List members'
    > > declared co-ordinates and to what geodetic framework they refer.
    > A most interesting discussion.   In many cases, I suspect the
    > answer to "which datum?" is "nary a clue."  In my own case,
    > pre-NIMA and pre-Heavens Above, I scrounged coordinates
    > from atlases, airport and weather site databases, wherever.
    > Few if any of those gave the datum used.
    > - Which datum is preferred today and should be used when possible?
    > (I'd guess WGS84.)
    > - If the datum is unknown, what level of accuracy should be reported and
    > used?  I.e., where do the coordinates given in decimal degrees diverge
    > in the commonly used systems?  The current standard in this community
    > seems to be four places after the decimal point, 10 meters, around GPS
    > accuracy.  Does that demand specifying the datum?
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    Dr. Jörg Kampmann - IBK-Consult for Real-Time and Embedded Systems
    D-31228 Peine - Tel.:+49-177-276-3140 - Fax: +49-5171-13385
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