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Is there any open-source library to aggregate detached polygons? I know that there is a tool in ArcInfo, but it is commercial.

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Knowing which tool in ArcInfo are you trying to replicate would be helpful. Are you referring to the Dissolve function? or something else? – RyanDalton Apr 30 '12 at 17:57
I assume Sanjeewa means the actual 'Aggregate Polygons' tool (requires ArcInfo). In ArcGIS 10 it is under the Generalization tools of the Cartography toolbox. It produces a sort-off concave-hull for want of a better term. – MappaGnosis May 3 '12 at 14:02

4 Answers

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PostGIS has a ST_ConcaveHull function which equates closely to the Aggregate Polygons function of ArcGIS. Sadly Spatialite does NOT have this function.

A concave hull can be thought of as a "shrink-wrapped" convex hull.

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if you have PostgreSQL, there is a sql function which have been writed from Dr. Horst Duester. he has two sql code, one is for Orthogonal Aggregation of Buildings and another is for non Orthogonal Aggregation... you can find sql codes here.

it determines edge of objects very good way with defination of threshold..and its query is so easy to use:

Query:

select aggregatepolygons(wkb_geometry, 50, true) from buildings group by art;

Examples:

Orthogonal Aggregation of Buildings

figure 1

Non Orthogonal Aggregation of Natural Objects

enter image description here

i hope it helps you...

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Yes, thanks a lot – Sanjeewa May 9 '12 at 9:29
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Try the Java Topology Suite (JTS). There is a user guide which has a heading "How to Union Many Polygons Efficiently".

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Also, Sextante is a GIS library for Java. It may include that functionality - http://www.sextantegis.com/

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