[gdal-dev] openFileGDB driver - polygons with bezier curves not exporting correctly

[obrl soil]

Hi,

Cross-posting from
https://gis.stackexchange.com/questions/264026/gdal-and-openfilegdb-driver-polygons-with-bezier-curves-not-exporting-correctl

System: Win 7, OSgeo4W package 64 bit (current to 3/12/17), GDAL 2.2.3

I have been provided with a polygon layer in ESRI FileGDB format
(created in ArcMap v10.3 at least, maybe 10.4 or 10.4.1). The polygons
in the layer have been digitised using a mix of straight line segments
and bezier curves / true arcs, which I've verified in ArcMap by
looking at the geometry in edit mode.

GDAL > 2.2.0 should be able to read and export CURVE-type geometries
correctly (e.g. to GPKG, which can support those geometry types) but I
can't get the export to work; e.g.

    # OGR_SKIP just forces use of OpenFileGDB driver, but the
    # same thing happens with either:

    ogr2ogr --config OGR_SKIP FileGDB -f GPKG C:/DATA/output.gpkg
C:/DATA/input.gdb LAYERNAME

still converts all the curves to a million tiny straight line
segments. The output file size balloons to ~300MB (from an 8MB source
file), making the data almost impossible to use. Even plotting is
difficult, forget any further geometric ops. Trying to force the issue
with -nlt CURVEPOLYGON has had no effect. Opening the layer in QGIS
2.18.14 produces the same results, as does import to R with
sf::st_read (these two rely on GDAL 2.2.3 and 2.2.0 respectively to
access GDBs on my machine).

ogrinfo reports the geometry type for the layer as Multi Polygon, as
does QGIS - and even Arc itself reports them as 'Polygon' in its own
Layer Properties interface, but I don't think the Feature Class
definition distinguishes between different polygon types.

Is this a GDAL bug (eg driver mis-detecting geom type) or an Arc bug
(eg some kind of failure to metadata properly)?

The gdb in question is at
https://github.com/obrl-soil/bits-n-pieces/tree/master/curvepolys

thanks,
Lauren