How can I read with 'deegree' a GML3.2 with an arc?

The simplified data contains an arc:

              <gml:posList>44.605 773.516 40.806 775.320</gml:posList>
              <gml:posList>40.806 775.320 38.522 759.491</gml:posList>
              <gml:posList>38.522 759.491 45.178 773.702</gml:posList>
              <gml:posList>45.178 773.702 44.930 773.491 44.605 773.516</gml:posList>

When performing this method

GMLObject gmlObject = null;
XMLStreamReader r = XMLInputFactory.newInstance().createXMLStreamReader(new StringReader(gml));
GMLStreamReader gmlStreamReader = GMLInputFactory.createGMLStreamReader(gmlVersion, r);
gmlObject = gmlStreamReader.read(); // --> error 1
gmlObject.toString(); // --> error 2

I get these errors:

  1. Method threw 'java.lang.IllegalArgumentException' exception. Cannot evaluate org.deegree.geometry.standard.primitive.DefaultPolygon.toString()
  2. java.lang.IllegalArgumentException: Cannot determine control points for ring, contains non-linear segments.

How to cope with this issue?


1 Answer 1



[The GML is not valid] -> I suppose that deegree thinks that the GML is not valid, because the upper level element is <gml:Polygon>, and by some definitions polygons can contain only straight segments. Maybe therefore <gml:Arc> that appears deeper in the data gives an error.

Arc and other curved element are allowed in a PolygonPatch https://datypic.com/sc/niem21/e-gml32_PolygonPatch.html.

  • Is the above really true? Other systems can work with arcs within a polygon. This is what I can find: datypic.com/sc/niem21/e-gml32_Polygon.html. You can click on polygon > exterior > ring > curveMember > curve > segments > arc.
    – tm1701
    Commented Sep 15, 2023 at 13:06
  • 1
    I edited the answer to ponder if that's how the deegree software is analyzing the GML.
    – user30184
    Commented Sep 15, 2023 at 17:19

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