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<p>Benoit,</p>
<p>Indeed OGR_L_GetExtent() will never fill the Z fields, since it has no idea they are there. So a 3D specific function would be needed.</p>
<p>But in the case of GeoPackage, as many/most other formats, layer extent metadata doesn't include the Z component either. The generic option is to iterate over all features and use OGR_G_GetEnvelope3D() on their geometry.</p>
<p>In the specific case of GeoPackage, you could also issue a ExecuteSQL("SELECT MIN(ST_MinZ(geometry_column_name)), MAX(ST_MaxZ(geometry_column_name)) FROM layer_name") which should be faster on big layers</p>
<p>Even
</p>
<div class="moz-cite-prefix">Le 23/06/2023 à 11:14, B. De Mezzo a
écrit :<br>
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cite="mid:9d6ab5a5-4179-e486-8f2d-4253ee72cd8d@oslandia.com">
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<p>Hi,</p>
<p>I was looking for a solution to retrieve a 3D extent (in my case from a gpkg). Currently, the OGR_L_GetExtent function uses an OGREnvelope and when I pass a OGREnvelope3D parameter, it does not fill the Z fields. </p>
<p>What should be the best approach to the minZ and maxZ for a layer?</p>
<p>Regards.
</p>
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