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<p>Thanks for the update, this make sense.</p>
<p>For info, EPSG geodetic dataset defines a transformation from
NAD27 to NAD83 using the "conus" files as you did, followed by a
transformation from NAD83 to NAD83(HARN) (one of the new NAD83
definitions created after the original one) one the assumption
that NAD83(HARN) is equivalent to WGS84 within the accuracy of
the transformation. The later transformation is using other
grids depending on the geographic area (I didn't saw a grid for
the whole US for the NAD83 to NAD83(HARN) part, but maybe I
didn't searched hard enough).</p>
<p> Martin</p>
<p><br>
</p>
Le 14/06/16 à 01:15, Jody Garnett a écrit :<br>
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cite="mid:CAOhbgA=ATyE2zUyMm9=Hiz=zq1sG2y+-9QWP_X+c4afJj2a1-g@mail.gmail.com"
type="cite">
<div dir="ltr">Just wanted to report back to this email thread,
although I was never able to determine quite what PROJ4 was
doing but we were able to use a series of points to make an
educated guess:
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<div>The fix, at least for me, was to define a customer <b>epsg_operations.properties</b>
file that combined the grid-shift transform (from NAD27 -->
NAD83) and the shift from NAD83 --> WGS84):<br>
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<div> 4267,4326=CONCAT_MT[ \</div>
<div> PARAM_MT["NADCON", \</div>
<div> PARAMETER["Latitude difference file",
"conus.las"], \</div>
<div> PARAMETER["Longitude difference file",
"conus.los"]], \</div>
<div> PARAM_MT["Molodenski", \</div>
<div> PARAMETER["dim", 2], \</div>
<div> PARAMETER["dx", 0.0], \</div>
<div> PARAMETER["dy", 0.0], \</div>
<div> PARAMETER["dz", 0.0], \</div>
<div> PARAMETER["src_semi_major", 6378137.0], \</div>
<div> PARAMETER["src_semi_minor",
6356752.314140356], \</div>
<div> PARAMETER["tgt_semi_major", 6378137.0], \</div>
<div> PARAMETER["tgt_semi_minor",
6356752.314245179]]]</div>
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<div><br>
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<div>This has output between GeoServer and QGIS lining up
sufficient for the application I am working on.</div>
<div>--</div>
<div>Jody</div>
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