[gdal-dev] Unable to extract features from KML

[Michael Z Freeman]

Hi,

Still having trouble with this after updating to ogr2ogr/gdal 2.1.1.

Some of it is undoubtedly my unfamiliarity with GDAL. I'm on the steep
part of the learning curve ! But fun.

"ogr2ogr -f PostgreSQL PG:"dbname=original_hirise" -a_srs "EPSG:4326" -lco
OVERWRITE=YES -explodecollections -nlt geometry
Beyer_Hirise_Areas_KML/MC-01-0-0-0.kml"

... creates (an edited CSV exported from a PGAdmin4 query) ...

"ogc_fid","name","description","wkb_geometry"
1,"ESP_018108_2680","[...]","0101000020E61000000AD7A3703D6A3EC0744694F606035640"
2,"ESP_018108_2680","[...]","0103000020E61000000100000005000000A4703D0AD7233CC079E9263108FC55400000000000C03FC0F4FDD478E9FA5540F0A7C64B377940C0992A1895D4095640FCA9F1D24DE23CC002BC0512140B5640A4703D0AD7233CC079E9263108FC5540"
3,"ESP_018318_2675","[...]","0101000020E6100000A245B6F3FD543EC0728A8EE4F2DF5540"
4,"ESP_018318_2675","[...]","0103000020E610000001000000050000004260E5D0223B3BC00C022B8716D95540AAF1D24D62503DC0FED478E926D55540448B6CE7FBD940C0C364AA6054E6554039B4C876BE7F3FC06D567DAEB6EA55404260E5D0223B3BC00C022B8716D95540"

As you can see the geometries from the KML are exploded ... the short WKB
is a point, the longer one POLYGON geometry. However two database entries
are created for each feature ("name"). I could just merge these but I feel
that OGR can create two geometry columns each for POINT and POLYGON, in
fact this seems to be explicitly stated that it can do this in the news
release for GDAL version 2.

Should I be using some kind of SQL statement on the OGR command line to
make it do this ?

Michael Z Freeman

On Mon, November 21, 2016 7:30 am, jratike80 wrote:
> Hi,
>
>
> The main problem is that KML support such data models which do not suit
> well with the simple feature model of GDAL. You can get some information
> about that by reading http://www.gdal.org/drv_libkml.html.
>
> In your case each feature has two geometries: one point and one polygon.
> Best that can be done with the simple feature model it to push them both
> into one geometry which in that case must be a geometry collection. Here
> is one example from your data
>
> GEOMETRYCOLLECTION (POINT (-1.282 87.1064),POLYGON ((3.02457
> 87.0792,2.22294
> 86.9806,-5.655 87.1168,-5.098 87.2201,3.02457 87.0792)))
>
>
> You can save geometry collections into PostGIS if you use ogr2ogr with
> switch "-nlt geometry". However, saving geometry collections into PostGIS
> may not solve your problem because only few GIS programs can handle
> geometry collections well.
>
> A better option for you might be to explode the collections and save
> points and polygons as separate features into PostGIS. The ogr2ogr command
> to use is like
>
> ogr2ogr -f PGDump output_pgdump -nlt geometry -explodecollections
> Beyer_Hirise_Areas_KML/MC-01-0-0-0.kml
>
>
> If you want to have a quick look at your data, use JML as outputformat
> and open the result with OpenJUMP. It shows both the geometry collections
> and exploded collections fine for me with names and descriptions.
>
> -Jukka Rahkonen-
>
>
>
>
> --
> View this message in context:
> http://osgeo-org.1560.x6.nabble.com/gdal-dev-Unable-to-extract-features-f
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