I have CAD-data which I transformed to shapefiles. Currently after the transformation the objects still have a Z value which is useless to me.

My question is: How do I convert a MultiLineStringZ-object to a MultiLineString-object?


There is a ST_Force2d function in PostGIS which does the job. A new table should be created with 2D geometry and use an insert statement with select to populate the new table:

insert into new_table (geom, col1, col2, col3) 
select ST_Force2D(geom), col1, col2, col2 from old_table;

You should substitute your real column names into col1, col2, ... You can query the table structure with in psql

\d old_table

or you can use pgadmin with GUI.

  • Could you accept my answer clicking on the up arrow beside my answer? – Zoltan Dec 28 '18 at 10:48

Run the drop z values algorithm from the QGIS processing toolbox

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