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<p>Michael,</p>
<p>A general solution would have more appeal, although I suspect it
will be a bit more computation intensive as you'll probably have
to transform to invoke PROJ multiple times per grid point to
compute the direction to the North</p>
<p>Even<br>
</p>
<div class="moz-cite-prefix">Le 25/06/2021 à 06:29, Michael Sumner a
écrit :<br>
</div>
<blockquote type="cite"
cite="mid:CAAcGz9_wAWd2dse4qGLkydzW1pAY2tsAC3e8Wn0WNAE4_WbAJw@mail.gmail.com">
<div dir="ltr">Hello, we're using `gdaldem aspect` on polar grid
products and we need to convert the grid-oriented directions to
compass oriented ones, location-specific directions, where
"compass north" is dependent on longitude.
<div><br>
</div>
<div>It's easy but inefficient for us to do this after running
gdal dem for our polar grids at latitude -90, and a more
general solution would require a general approach to "where
north is" for any location in a projection. </div>
<div><br>
</div>
<div>I'll be able to modify GDAL to do this as an option to
gdaldem for a simple polar grid (e.g. EPSG:3031), and that
will make our use of it much more efficient. Is there any
interest in a more general approach? </div>
<div><br>
</div>
<div>Best, Mike</div>
<div><br>
</div>
<div><br>
<div><br>
</div>
-- <br>
<div dir="ltr" class="gmail_signature"
data-smartmail="gmail_signature">Michael Sumner<br>
Software and Database Engineer<br>
Australian Antarctic Division<br>
Hobart, Australia<br>
e-mail: <a href="mailto:mdsumner@gmail.com" target="_blank"
moz-do-not-send="true">mdsumner@gmail.com</a></div>
</div>
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<br>
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