[mapserver-users] Intersect and Union with mapserver

[Rahkonen Jukka]

saka royban wrote:

> Finally, as Jukka talked about QGIS. This is a little confusing to me. In a
> web mapping application which is implemented by MapServer, Can we rely on
> QGIS capabilities and use the in our application? If so, how would be the
> connection between MapServer and QGIS.

I wanted to emphasize the difference in the meaning of "union" for ESRI and for PostGIS and most other open source GIS programs as well as for the Open Geospatial Consortiom. For the latter group union means the same as "dissolve" for ESRI as illustrated in http://resources.arcgis.com/en/help/main/10.1/index.html#//00170000005n000000. QGIS was just an example of programs which understand union in the other way than ESRI.

I am not sure about how to do the "union" as ESRI understands it with PostGIS and SQL. I guess that first you should create new geometries by clipping the polygons on layers A and B and then transfer the attributes from layers A and B to the new geometries by using a spatial join.

-Jukka Rahkonen-



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