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I am trying to create lines parallel to some road centerlines, using distances from the attribute table specific to each line. I'm trying to figure out how to get it to save to a new table with geometry that I can view in qgis or arcgis. I've imported the source data (which was a shapefile) into a postgres database, and ran this query:

select ST_OffsetCurve(
test_data_.geom, test_data_.buffer_dis, 'join=mitre mitre_limit=5.0')
into test_data_left from test_data_;

It writes out to a new table called test_data_left as specified above, but I can't see this table (or the original for that matter) in either qgis or arcgis, when I try to load directly from the database. I tried to export the test_data_left to shapefile, which it does, but when I try to laod it in qgis it appears to be empty, and arcgis tells me the number or shapes don't match the number of records. I think I am missing a step or two. I'd also like to be able to associate some of the fields in the original table with the ouput but am not sure how to do that in this expression?

UPDATE:

I found this useful thread Creating a spatial PostGIS table as a result of a PostGIS query and am working on adding geometry and ID fields, hoping that will get me part of the way there. Still looking for a way to add some of the original fields and values to the output as well.

  • Are input geometries linestring? – WKT Apr 19 '16 at 17:37
  • yes they are, ST_offsetcurve won't work with multilinestrings I had to convert to linestring – kflaw Apr 19 '16 at 17:39
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First, use only the select and st_astext() to check the results: (adapt to your fields)

select test_data_,id_field,test_data_.geom,st_astext(ST_OffsetCurve(
test_data_.geom, test_data_.buffer_dis, 'join=mitre mitre_limit=5.0'))

If all right then:

select test_data_,id_field,test_data_.geom,ST_OffsetCurve(
test_data_.geom, test_data_.buffer_dis, 'join=mitre mitre_limit=5.0')
into test_data_left from test_data_;
  • that is so simple and exactly what I need, thank you! When i export to shapefile i can see everything looks right. The only issue i am still having is that I can't see the data in the database when i try to connect to it either with qgis or arcgis? – kflaw Apr 19 '16 at 20:16
  • Oops I see now it was a permissions thing. thanks again! – kflaw Apr 19 '16 at 20:19

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