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<p>Kirk,</p>
<p>the relationship between a transformation and its area of use is
now done through an entry in the usage table.</p>
<p>See
<a class="moz-txt-link-freetext" href="https://github.com/OSGeo/PROJ/blob/dcc2a94eb1c5eda5ede6275b58ae5873e78bb9c0/data/sql/helmert_transformation.sql#L2244">https://github.com/OSGeo/PROJ/blob/dcc2a94eb1c5eda5ede6275b58ae5873e78bb9c0/data/sql/helmert_transformation.sql#L2244</a></p>
<p>Even<br>
</p>
<div class="moz-cite-prefix">Le 03/06/2021 à 22:03, Kirk Waters -
NOAA Federal a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:CADm=QrSL0QU0J+qJ49gNdD4x8qUUAZt5GpkoRm9DotLzrDWxSA@mail.gmail.com">
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<div dir="ltr">Even,
<div>I decided to script out adding the transforms to the
proj.db file so I can automatically have my system add them
when new proj.db files get released. One thing I haven't
figured out is how the extent is associated with the
transform. For 8971, I don't see anything in the
helmert_transformation table that looks close except the
'IOGP-Usa GoM' for the operation version. EPSG.org shows the
extent code for transform 8971 is 3357, which matches what I
find in the extent table, but I don't see where in proj.db
that's happening. The name for extent 3357 is 'USA - GoM OCS',
so it doesn't match the helmert_transformation entry for 8971.
Apologies if I'm asking something that's clearly laid out. I
just haven't found the right docs yet.</div>
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<div dir="ltr" class="gmail_signature"
data-smartmail="gmail_signature">
<div dir="ltr">Kirk</div>
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<div dir="ltr" class="gmail_attr">On Thu, Jun 3, 2021 at 6:49 AM
Even Rouault <<a href="mailto:even.rouault@spatialys.com"
moz-do-not-send="true">even.rouault@spatialys.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><br>
Le 03/06/2021 à 12:37, Kirk Waters - NOAA Federal a écrit :<br>
> Even,<br>
> Thank you very much, that's very helpful. It's along the
lines of what <br>
> I was thinking was the problem, but I hadn't gotten far
enough to <br>
> realize I could add an entry in the database. The other
option is to <br>
> figure out the right EPSG code to pass to GDAL to pretend
the <br>
> transform has already happened.<br>
<br>
If you use gdalwarp, you can lie a bit and set -s_srs
EPSG:2273 to force <br>
"NAD83 / South Carolina (ft)" as the source CRS, and then
you'll get the <br>
transformation to NAD27 using the CONUS grid.<br>
<br>
Even<br>
<br>
<br>
-- <br>
<a href="http://www.spatialys.com" rel="noreferrer"
target="_blank" moz-do-not-send="true">http://www.spatialys.com</a><br>
My software is free, but my time generally not.<br>
<br>
</blockquote>
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</blockquote>
<pre class="moz-signature" cols="72">--
<a class="moz-txt-link-freetext" href="http://www.spatialys.com">http://www.spatialys.com</a>
My software is free, but my time generally not.</pre>
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