openlayers geojson GeometryCollection serialize - geometry

Question

I tried to add a geojson GeometryCollection (two polygons in one feature) with the following code:
var featurecollection = {"type":"Feature", "properties":{"WKR_NR":{"value":"66", "displayName":"WKR_NR"}, "WKR_NAME":{"value":"Altmark", "displayName":"WKR_NAME"}, "LAND_NR":{"value":"15", "displayName":"LAND_NR"}, "LAND_NAME":{"value":"Sachsen-Anhalt", "displayName":"LAND_NAME"}}, "geometry":{"type":"GeometryCollection", "geometries":[{"type":"Polygon", "coordinates":[[[11.82209622587612, 52.34301860166207], [11.817774093487138, 52.334218350541896], [11.807618922039657, 52.334988060217924], [11.790223804374884, 52.3372550858293], [11.78804671117088, 52.35066482829717], [11.80055500070333, 52.35470147787753], [11.819318685600722, 52.34773879534134], [11.82209622587612, 52.34301860166207]]]}, {"type":"Polygon", "coordinates":[[[11.625490226126516, 53.014155173198034], [11.643792593971638, 53.005353749176265], [11.678605317048948, 53.007500272184636], [11.691508960695465, 52.97890177931147], [11.744900087714374, 52.98836377813224], [11.785485168911753, 52.96123819494062], [11.843231838584519, 52.953331343009545], [11.846841832814349, 52.940137809430865], [11.823030489231808, 52.92303250071203], [11.83682008625954, 52.90938467138226], [11.981941169062262, 52.87607203121912], [12.020385227153387, 52.88841247097549], [12.080988158376819, 52.88220894061335], [12.127289816840882, 52.88981664655036], [12.119895693664516, 52.87543803746719], [12.13248219200621, 52.8558211228031], [12.199403343824061, 52.8714428383796], [12.232750317016908, 52.86024742307424], [12.251497497148451, 52.809510687301696], [12.247443721853234, 52.791959611234866], [12.22364885088984, 52.785328135584855], [12.21227265368092, 52.77301936690752], [12.197091298456408, 52.7188147816694], [12.238613424621569, 52.665409856765734], [12.230258850787465, 52.62968330608261], [12.190385960758247, 52.6201934757329], [12.17515906502223, 52.60457261828375], [12.174433832794424, 52.58003052479018], [12.143361062323343, 52.53573113037129], [12.171210063866818, 52.5062636155928], [12.162640316645106, 52.500835395082156], [12.108195830773255, 52.50822883163489], [12.103168497725802, 52.52477556943423], [12.076814313382958, 52.54004044347858], [12.050694924487075, 52.525045881355894], [11.990420550370642, 52.52007883088814], [11.997901831632793, 52.571024464450616], [11.988240632385583, 52.57527707609638], [11.980151608981359, 52.53823974699831], [11.95970542521976, 52.51858066040097], [12.002753238668047, 52.460333327925404], [11.992708877983876, 52.43103249736487], [11.962270843821118, 52.400999345836794], [11.929241869486036, 52.39181373779316], [11.900270801301792, 52.35418951773055], [11.851935108210942, 52.33139272188436], [11.817433924211613, 52.372403339618714], [11.834328379190685, 52.38188020438711], [11.840446842567902, 52.40164092728919], [11.824000038133862, 52.421633313829446], [11.79788329849156, 52.4048537794548], [11.748126546321151, 52.403015286614185], [11.719844059178572, 52.409742937959756], [11.699715351222565, 52.459041056498315], [11.642991884388962, 52.47027254032829], [11.58745520968375, 52.458591499535565], [11.562455406690738, 52.41074571800978], [11.445607147252204, 52.386918975933064], [11.451253714966386, 52.40716604689364], [11.382327026093915, 52.43044308452597], [11.33303944763232, 52.42398398569652], [11.243861916949461, 52.43771185485013], [11.147647875850998, 52.43388371635617], [11.089960257644199, 52.455533659368896], [11.05650628403439, 52.5062061560478], [11.00865540209794, 52.49743833029479], [10.959367089863635, 52.534880501626205], [10.937115198576306, 52.56809668379479], [10.940699738434244, 52.58980058724528], [10.972900452451096, 52.60390715247509], [10.976957812353136, 52.624198440535906], [10.945210633577373, 52.62031889495053], [10.926765054712599, 52.60921629226031], [10.908807605370766, 52.62675394652262], [10.902900060583416, 52.63288635850292], [10.838250804892366, 52.69536905177916], [10.79667724408703, 52.71431343626516], [10.755698500874928, 52.78463211599313], [10.759750766469935, 52.79609356944849], [10.765414355239177, 52.8414963636739], [10.841955892273544, 52.85196752350796], [10.93957634429748, 52.85277462442411], [10.986189746274858, 52.88272387705999], [11.001678908430973, 52.91108170517689], [11.069342325527263, 52.909623974478905], [11.110626400886918, 52.89555950095206], [11.156283854647228, 52.90608086656519], [11.21878208126892, 52.89799790911749], [11.239884606905864, 52.879517541557206], [11.29579804373252, 52.875170703477764], [11.406571977621434, 52.904075444754625], [11.470842953571694, 52.938951093845404], [11.504592143927084, 52.941128094313925], [11.492348754753628, 52.95953308861247], [11.512383406030214, 53.00726268548251], [11.555636882784334, 52.998602963293635], [11.59617386672076, 53.0362803481102], [11.623050800347798, 53.041932006345355], [11.641148205721082, 53.0377603493648], [11.625490226126516, 53.014155173198034]]]}]}, "crs":{"type":"name", "properties":{"name":"urn:ogc:def:crs:OGC:1.3:CRS84"}}};
var geojson_format = new OpenLayers.Format.GeoJSON({
'internalProjection': new OpenLayers.Projection("EPSG:900913"),
'externalProjection': new OpenLayers.Projection("EPSG:4326")
});
vectors.addFeatures(geojson_format.read(featurecollection));
The polygon is shown quite well, as you can see here:
http://217.16.163.138/flaechen.php
With a click on the polygon the function "serialize" is triggered and the geojson-code is written in an output-box:
var type = "geojson";
var pretty = false;
var str = formats['out'][type].write(feature, pretty);
str = str.replace(/,/g, ', ');
document.getElementById('output_featureonly').value = str;
The problem is that the projection of the polygon is changing to something realy strange.
The code works well for only one polygon in one feature. You can try it on your own here:
http://217.16.163.138/flaechen.php
Thanks in advance
Florian

Answer 1

It does not look like OpenLayers supports this type, or at least not presented in this way:
http://dev.openlayers.org/docs/files/OpenLayers/Format/GeoJSON-js.html#OpenLayers.Format.GeoJSON.read
For multiple polygons the type should be 'MultiPolygon':
http://www.geojson.org/geojson-spec.html#multipolygon
Try reducing the input to a minimal test case it should be easier to debug.