OpenLayers.Format.GML.parseFeature() with GML v3 data

Question

I have a partial GML object with the geometry type polygon. The GML version must be 3+ since the coordinates are wrapped in the gml:posList tag:

<gml:Polygon srsName="EPSG:25832" xmlns:gml="http://www.opengis.net/gml">  
     <gml:exterior>  
         <gml:LinearRing srsName="EPSG:25832">  
             <gml:posList>
                 N points where N is an even integer.
             </gml:posList>  
         </gml:LinearRing>  
     </gml:exterior> 
</gml:Polygon>

I am using OpenLayers 2.10 and I am trying to convert the GML object into an OpenLayers feature using the OpenLayers.Format.GML class.

When executing the parseFeature method, which later calls the parseGeometry.linestring I encounter this comment:

/**
* Two coordinate variations to consider:
* 1) <gml:posList dimension="d">x0 y0 z0 x1 y1 z1</gml:posList>
* 2) <gml:coordinates>x0, y0, z0 x1, y1, z1</gml:coordinates>
*/

And this line of code which assumes the dimension attribute to be present:

var dim = parseInt(nodeList[0].getAttribute("dimension")); 

In OpenLayers.Format.GML.v3 the same line of code looks like this:

var dim = parseInt(node.getAttribute("dimension")) || 2;

The problematic difference for me is the || 2 part which assumes that a missing dimension means 2 dimensional - which is what I want. Then why not use the v3 edition, but the OpenLayers.Format.GML.v3 does not implement the parseFeature method.

I am recieving GML features from various services and I do not control them.

What is the best approach to handle this problem?

Answer 1

After a quick glance it looks like the v2 and v3 JS files derive from base (definitely makes sense too) which offers a read method. Try checking that out.

See: http://github.com/openlayers/openlayers/blob/2.x/lib/OpenLayers/Format/GML/Base.js#L151

If that is not complete or does not meet your needs you can just modify the source. Given the generous licensing and the nature of JavaScript you could just add it in yourself or better yet create a pull request for that change.

See: http://github.com/openlayers/openlayers/blob/2.x/lib/OpenLayers/Format/GML.js#L348

If you feel the need to hack something messy together you can also add that attribute to the nodes:

setMissingDefaults = function(node){ /* magic stuff */ }
OpenLayers.Format.GML.parseFeature(setMissingDefaults(node));