What does geoserver do when you get a result set from a postgis layer that contains multiple Geoshaps (of type multipolygon) that overlaps the same area?

Does geoserver add the two overlapping values together and middle (average) them or does it only show one of the values or does it add them together without middling them?

Edit: ive added an example that shows two maps - and then the the third image is the result from asking for both the maps - but without doing any aggregation. So geoserver will get polygons for two areas - and it looks like geoserver is applying some function to average or merge the two layers.

Edit2: If geoserver doesnt do any aggregation - is it possible in sld to add aggregation function like avg or sum?

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  • What do you mean by "middle them"? Geoserver renders polygons according to the SLD. Jul 3, 2014 at 8:53
  • I mean take the average.
    – Endre Moen
    Jul 3, 2014 at 8:53

1 Answer 1


By default, It will show both the polygons without any merging or averaging , and the result of GetFeatureInfo on the WMS service will return results from each of the polygons.

  • but if they are overlapping - and say styled with color from blue to red - only one of them will show. So say one layer is blue the other is red. Then you cannot show both layers - blue and red in the same area. It should be pink - but will it be blue or red instead?
    – Endre Moen
    Jul 3, 2014 at 10:06
  • I believe that you will get faster and better answer by trying it yourself. I would put some transparency into styles.
    – user30184
    Jul 3, 2014 at 10:30
  • They are drawn in featureID order to be precise.
    – Ian Turton
    Jul 3, 2014 at 11:11
  • Ive added an example and from the example it doesnt look like the layer is drawn in featureID order - but instead it looks like geoserver is averaging or merging the two layers.
    – Endre Moen
    Jul 3, 2014 at 11:33

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