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    <p>Javier,</p>

    <br>

    <blockquote type="cite"

cite="mid:CADRrdKvDEo_c9qA7mzam58G3CQmv7SRfb3tnk9RjkLf1sTytkA@mail.gmail.com">

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        <div>Is there already a way to define a geoid model interpolated

          in projected coordinates?</div>

        <div>(some "small" countries, with just one projection, define

          their geoid models in that projected CRS. Recreating the grid

          in a geographic one adds some error)</div>

        <div><br>

        </div>

        <div>I see that <a

href="https://proj.org/en/stable/operations/transformations/gridshift.html"

            moz-do-not-send="true" class="moz-txt-link-freetext">https://proj.org/en/stable/operations/transformations/gridshift.html</a>

          was added in 9.2.0, but I only see these options:</div>

        <div>HORIZONTAL_OFFSET,</div>

        <div>GEOGRAPHIC_3D_OFFSET,</div>

        <div>ELLIPSOIDAL_HEIGHT_OFFSET,</div>

        <div>VERTICAL_OFFSET_GEOGRAPHIC_TO_VERTICAL,

          VERTICAL_OFFSET_VERTICAL_TO_VERTICAL.</div>

        <div><br>

        </div>

        <div>I am not sure if any of those apply as

          "VERTICAL_OFFSET_PROJECTED_TO_VERTICAL".</div>

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    </blockquote>

    <p>This is a bit untested area.

      VERTICAL_OFFSET_GEOGRAPHIC_TO_VERTICAL should be the one to use I

      believe.</p>

    <blockquote type="cite"

cite="mid:CADRrdKvDEo_c9qA7mzam58G3CQmv7SRfb3tnk9RjkLf1sTytkA@mail.gmail.com">

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        <div>In case it is possible, how would be the insertion of the

          transformation in proj.db? (something like <a

href="https://github.com/OSGeo/PROJ/blob/master/data/sql/grid_transformation_custom.sql#L71"

            moz-do-not-send="true" class="moz-txt-link-freetext">https://github.com/OSGeo/PROJ/blob/master/data/sql/grid_transformation_custom.sql#L71</a>)</div>

      </div>

    </blockquote>

    <p>You likely need to use a PROJString with +proj=gridshift

      +grids=...</p>

    <p>Even</p>

    <span style="white-space: pre-wrap">

</span>

    <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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