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<DIV>I understand the need for the first and last point but what I don't understand is why it is not handled appropriately (in my opinion) per format. If KML only wants 4 points for a rectangle and other formats want 5 (first and last point the same) why doesn't the import/export function build the shape to an internal standard (ie have everything load in with the first point repeated at the end). I tried importing a shapefile into an OGRDataset and then exported it out to KML only to have Google Earth hang on the resultant KML file. This obviosuly implies that I would have to implement vector format specific implementations, is there a reason for this?</DIV>
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<DIV>Christiaan<BR></DIV>
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<B>From:</B> Nikos Alexandris [mailto:nikos.alexandris@felis.uni-freiburg.de]<BR><B>To:</B> Christiaan Janssen [mailto:cjanssen@iavo-rs.com]<BR><B>Cc:</B> gdal-dev@lists.osgeo.org [mailto:gdal-dev@lists.osgeo.org]<BR><B>Sent:</B> Wed, 12 Mar 2008 16:09:45 -0400<BR><B>Subject:</B> Re: [gdal-dev] Shapefile OGR question/concern<BR><BR><BR>On Wed, 2008-03-12 at 21:05 +0100, Nikos Alexandris wrote:<BR>> On Wed, 2008-03-12 at 15:48 -0400, Christiaan Janssen wrote:<BR>> > Hi all,<BR>> > I'm having an issue with the Shapefile driver within OGR. When<BR>> > exporting data from an OGRDataset to a shapefile I'm required to add<BR>> > an additional "closing point" (ie repeat the first point at the end)<BR>> > for the resultant shapefile to be correctly recognized in other<BR>> > viewers (I realize the shapefile spec calls for this). The problem is<BR>> > that other formats do not require this closing point (eg KML) and<BR>> > adding the additional point results in additional point being written<BR>> > to the outputted file, not what I would believe to be correct. It<BR>> > would seem then that depending on my output I would have to reformat<BR>> > my data, seemling defeating the purpose of having an interfaced method<BR>> > library like OGR. Am I incorrect in my assumption and/or is there<BR>> > another intended way to do this correctly. <BR>> <BR>> I am sure that you will get "better" replies to this from the Experts.<BR>> But I'll give it a shot since I had a similar issue.<BR>> <BR>> The "closing point" has to be there in case you are dealing with closed<BR>> polygons (areas). Without it (in other words without first and last<BR>> point identical) polygons are not really "closed" and therefore<BR>> topologically not "clean".<BR>> <BR>> Non-topological formats like ESRI Shapefiles can live with that and<BR>> therefore cleaning is highly recommended.<BR>> <BR>> .<BR>> <BR>> Some weeks ago I was trying to import KML's polygons into GRASS the data<BR>> appeared broken (open polygons, missing lines (?) and even a centroid<BR>> falling outside an area (?))<BR><BR>I hope I added more questions (rather than answering) so I understand<BR>all this bymyself ;-P<BR><BR>Any KML experts?<BR><BR></BLOCKQUOTE>
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