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Staff
Posts: 33
Registered: ‎02-27-2018

Geometry Collection in a Composite Polyline Geometry

I would line to be able to "flatten" a GeometryCollection in a single CompositePolylineGeometry.

 

My GeometryCollection is made of 3 CompositePolylineGeometry (see attachement) and the order of the point within the polyline and between the polyline matters.

 

I tried to use a functional attribute GEOMETRIES to split the collection and then to MERGE them als a single polyline but without success.

I also tried COMPRESS, but to no avail as I got the same result as the initial situation.

 

Do you have any ideas of tools/functions in GeoMedia (or in the Oracle Database directly) I could combine to get to my desired result, which is a single CompositePolylineGeometries with all my lines and point in the right order?

Technical Evangelist
Technical Evangelist
Posts: 306
Registered: ‎02-03-2016

Re: Geometry Collection in a Composite Polyline Geometry

My immedediate reaction is that the COMPRESS function is the right answer.  It is intended to do what you wish.  From its help topic:

 

COMPRESS

The process of optimization involves three different activities:

  1. Nested composites/collections are flattened. This eliminates geometry headers, eliminates recursive processing, and (for composites) sets the stage for further optimization in the next step.
  2. Consecutive endpoint-matched lines/polylines within composites¹/collections² are stitched together into a single polyline. This eliminates geometry headers and eliminates redundant vertices.
  3. Single-member composites/collections are flattened and replaced with the single member primitive. This eliminates the parent geometry and simplifies processing.

 

Obviously I am concerned that you indicate it does not work for your case.  In your diagram I can't see "inside" the first two composite polylines, but the much-smaller third one does have an arc in it so it would not compress at all.  If the much larger first two also have arcs, then that would interfere with achieving the complete effect you seek.  Still, any time in which there were consecutive polylines (or composite polylines) within them, it should simplify things.  It may be that you will need to log a support ticket to have the data examined by our support staff.  - Hal

Occasional Contributor
Posts: 11
Registered: ‎03-22-2016

Re: Geometry Collection in a Composite Polyline Geometry

Because your geometry contains arcs, I don't believe you can create a single geometry.  The only way I've ever found to stroke arcs is by exporting the data to shape file, then re-importing into Oracle.  A tip, use an Oracle tool like SQL*Plus to copy your column names into a text file.  Since the shape file export will truncate the column names, it's much easy to copy the column names from the text file that trying to retype them during the import.

Highlighted
Staff
Posts: 33
Registered: ‎02-27-2018

Re: Geometry Collection in a Composite Polyline Geometry

Hi Hal,

thanks for the detailed explanation. I do have other Arcs within the other composite polylines.

 

Before logging a support ticket, we will try to import the data a bit differently. The data are coming from a CAD and the polyline is crossing itself, which, in my opinion, results in GeoMedia making a GeometryCollection out of it instead of a PolyLine like by the other geometries (which are not crossing themselves).

Technical Evangelist
Technical Evangelist
Posts: 306
Registered: ‎02-03-2016

Re: Geometry Collection in a Composite Polyline Geometry

It may be that you are correct, that this is thet cause of it being a GeometryCollection.  But that would be unexpected for me.  A collection woudl naturally be formed when two linear geometries for a single feature instance are disconnected/discontinuous, but not when they simply cross (which is valid for linear data though not of course for an area boundary).  I will be curious to hear what you learn from your experiments.  - Hal

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