Re: Geodetic precision

From: Kevin Fetter (
Date: Thu Aug 16 2001 - 22:27:25 PDT

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    While our tracking programs use WGS72 as the datum, the earth is now being 
    measured in the ITRF datum. ITRF stands for International Terrestrial 
    Reference Frame. WGS84 is based off that.
    While there is lots of datums, anyone with a gps receiver can obtain there 
    site position in WGS84. You can convert older positions in other datums to 
    the WGS84 position. But since tracking programs use WGS72, it doesn't matter 
    what datum you use, since there will be a loss in accurracy. I don't know if 
    norad is using the WGS 84 datum in there calculations but it might be time 
    to start using them. Surveyors use the ITRF datum, to measure the position 
    of survey markers, and gps orbits are in the ITRF datum.
    If I use a garmin gps25 receiver I can use the gps orbits to measure by 
    position, to around 3 meters or less, or the approx accurracy of the WAAS 
    system. Since alot of gps receivers are going to use WAAS, then it won't be 
    to hard to obtain an accurate position.
    My question is what datum is used in the calculations of ted molczan, mike 
    mccants and others when they take observations and generate an orbit. Maybe 
    its time we sat observers agree on a datum to use when reporting positions 
    that also is used in orbit computations.
    Even though right now the orbits are quite good and we can find the object.
    Just a thought.
    I was wondering if anyone use a ccd camera not viedo camera for measuring 
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    This archive was generated by hypermail 2b29 : Thu Aug 16 2001 - 22:28:06 PDT