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Global reference datum change

  • 1.  Global reference datum change

    Posted 11-23-2022 11:38
    Can someone explain to me which option to use when? And what the differences are? 

    Backstory, field crew used the wrong epoch (2010) for a site. They set up a base with a known NEZ (previously processed to CanNet @ epoch 2002), and staked some points. When importing the field work to do some checks, I notice they used the wrong epoch, and switch it to the correct one, then I get the below dialog box.

    If I select the top one I have to shift my base points NEZ back to the known coordinates. If I select the bottom, there is no shift needed 



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    Jamison Ducolon
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  • 2.  RE: Global reference datum change

    Posted 11-23-2022 15:24
    If you select the first option check the grid coordinates of your As-staked points to see if they change. If you don't change then it probably doesn't matter what option you choose. However if they do change then you will want stay with the second option. 
    The as-stake deltas to these point will be based of the grid coordinates used when the point were staked. Even if the grid coordinates change, the deltas will stay the same. This is a record of how it was staked in the field (and possibly what was mark up on the stake), so you don't want these values changing. However it does mean that if the grid coordinates change they will no longer match the deltas.
    So your are 100% sure the that the points have been staked out in the correct place, I would probably go out to site and check a few of the as-staked points using a job with the correct epoch set.

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    James McWha
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