[mapserver-users] Dissolve Tool?

[Rahkonen Jukka]

Hi,
 
I guess that the "Union by attribute" function in OpenJUMP might be close to what you want (Tools - Analysis - One layer - Union by attribute value).  Download the nightly snapshot from http://openjump.org and unzip.  Increase Java memory setting in the launch file that is located in the \bin -directory. The file is openjump.bat for Windows, openjump.sh for Linux. The value you will need to increase is "-Xmx256M".  Try something like "Xmx1400M".  Lets hope it is enough for your dataset.  OpenJUMP keeps all the data in  memory and it is not sure that it can handle your data.  I am remembering that with 32 bit Windows it is not possible to increase memory above about 1500M even if the computer has more but I have read about 64 bit Linux user who was super happy with 6 gigabytes.
 
I had a try with Vmap0 World boundaries and union by REGION made me for example Europe and Asia multipolygons. Operation has an option for removing the common boundaries where it is possible, and another one for summing up the numeric fields. I suppose this is very close to what you want.
 
-Jukka Rahkonen-



________________________________

	Lähettäjä: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] Puolesta Lehr, Steven
	Lähetetty: 16. syyskuuta 2010 18:14
	Vastaanottaja: mapserver-users at lists.osgeo.org
	Aihe: [mapserver-users] Dissolve Tool?
	
	
	Does anyone have a reliable dissolve tool that they would share.  I have many cases where I need to dissolve parcels on a parcel_id (maybe up to 200,000 polygons in the whole file);  I know I can bring it down into ESRI, but it adds multiple steps to my process.  I'd like to have a Perl/python script that does:
	 
	dissolve.pl parcels parcel_id  
	 
	
	The output being a shapefile named parcels_dissolve.*
	 
	Where the inputs: parcels is a shapefile and parcel_id an attribute in the .dbf;  The .shp, .dbf etc would be processed appropriately dissolving on the attribute passed in, so it could be parcel_id to dissolve parcels with similar parcel_id, or could be an attribute like zoning; the resulting output file would contain only one record in the .dbf file for each unique attribute.  Additionally the only attribute left in the .dbf would be the attribute being dissolved on (unless you have the ability to sum area or count # of occurrences; but no other logic about which fields to bring forth; just the one attribute). 
	 
	Thanks for the help.  I'd be willing to pay for this project to be written if someone is interested - drop me an email off list.

	Steven Lehr
	Associate Professor
	College of Engineering
	Embry-Riddle Aeronautical University (LB263)
	600 S. Clyde Morris Blvd.
	Daytona Beach, FL 32114-3900
	386-226-7740
	  

	 
	 

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