Not too much response on this, but here was the question:
> Does anyone know of any software or data sets (shareware or commercial) that can
>convert elevation data from one vertical datum to another? Specifically, I'd like to
>convert some DEM data from NAVD 88 to NGVD 29.
And here are the answers:
Andrew Waltho <[EMAIL PROTECTED]> suggested I take a look
at Blue Marble's Geographic Calculator. Information about it was
at their website
(http://www.bluemarblegeo.com/products.asp?id=1), but in regards
to datum shifts in coordinates, only horizontal datums were
mentioned.
David Matson <[EMAIL PROTECTED]> pointed out the
web page for Corpscon at
http://crunch.tec.army.mil/software/corpscon/corpscon.html.
Corpscon is free software (for MS Windows) that converts
coordinates between geographic, State Plane and UTM for points in
the coterminous United States. Datum shifts are based on NADCON
And VERTCON, which are also free utilities.
Since I forgot to mention that Alaska was my region of interest,
VERTCON wasn't good enough as it doesn't cover Alaska. Further
inquiry drew a reponse from Renee Shields <[EMAIL PROTECTED]>
who said:
> "The VERTCON transformation is based on grids created from the differences between
>the NGVD29 and NAVD88 heights, but the vertical network is so sparse in Alaska that
>reliable grids could not be created. My best suggestion is that you locate a bench
>mark near the area in which you are working which has both NGVD29 and NAVD88 heights.
> A helpful tool to identify points is the NGSmap found on our web site under
>"Retrieve data sheets": http://www.ngs.noaa.gov/datasheet.html. If after working with
>this you are unable to locate a qualifying bench mark, contact our information center
>at [EMAIL PROTECTED], or, for occasional requests, contact me directly."
Thanks for the help, folks; I think I have a handle on it now!
- Bill Thoen
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