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Reproject vertical values from NGVD29 to NAVD88 without changing horizontal CS

  • July 17, 2020
  • 2 replies
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S

Hello!

I am working with polyline data that have known z-values derived from as-builts and inputted into a spreadsheet that was then used to plot the x, y, and z values. The vertical datum on these values were in NGVD29 but we need to convert the elevation values to NAVD88.

However, the horizontal coordinate system is already in NAD83, so CsmapReprojector using the "NAD27 heights in NGVD29; NAD83 heights in NAVD88" has no impact. Are there any alternative solutions that can be explored? I would really appreciate the help!

Best answer by daveatsafe

Hi @spizam,

I think the easiest solution would be to use two CsmapReprojectors in series - the first to reproject to NAD27 with no vertical adjustment, then second to reproject back to NAD83 with the vertical adjustment applied.

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daveatsafe
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  • daveatsafeSafer
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  • 1637 replies
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  • July 17, 2020

Hi @spizam,

I think the easiest solution would be to use two CsmapReprojectors in series - the first to reproject to NAD27 with no vertical adjustment, then second to reproject back to NAD83 with the vertical adjustment applied.

S
  • spizam
  • Author
  • 10 replies
  • July 17, 2020

Hi @spizam,

I think the easiest solution would be to use two CsmapReprojectors in series - the first to reproject to NAD27 with no vertical adjustment, then second to reproject back to NAD83 with the vertical adjustment applied.

Hi @daveatsafe, that was the perfect fix! Thanks so much :)

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