Last week I was told on a phone conference that GML supports shared boundaries in Polygon's. I have been unable to find any documenatation to substantiate the claim. Here is the situation:

I have a series of Polygons which represent areas in a forest. As a requirement for our operating license we have to submit these administrative boundaries to the government in a custom xml schema with the spatial data included as GML objects. I have a shape file which contains our polygons which was exported from our SDE. I then ran ogr2ogr on this shapefile to convert it into a GML file. I have a custom program that reads that GML file and then inserts the other information that the government requires.

The problem is the file is too large for the government site to accept, the original shapefile is 8.5 MB and the GML file is roughly 12.5 MB. Generalizing the shapefile isn't an option unfortunately because that alters the boundaries of the polygons and could lead to compliance issues.

Can GML Polygon, or MultiPolygons share boundaries? If so can someone point me to some documentation to that effect.

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    Can't you contact the site admin and request sending a zip? Or split the data into two files? – geographika Jul 5 '11 at 8:49

You should have a look on composite surface type :

A CompositeSurface is defined by a set of orientable surfaces. A composite surface is geometry type with all the geometric properties of a (primitive) surface. Essentially, a composite surface is a collection of surfaces that join in pairs on common boundary curves and which, when considered as a whole, form a single surface.

I think your unique option is to dive into GML specification. Particularly that document, see page 89.

(Byt the way, I never used such feature)

  • I wonder how many programs bother to implement that? – Ian Turton Jul 5 '11 at 10:28
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    No one, I guess ;-)) – simo Jul 5 '11 at 11:44
  • Thank you thank you that does indeed look like a solution now i just have to convince the Government guys to accept GML3 objects. I've never seen anyone implement that object in any conversions i've seen. :) – Gary.Townsend Jul 5 '11 at 15:57
  • Do you plan to implement it by yourself? – simo Jul 5 '11 at 16:56

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