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Not sure about that! If you know your data and know for a fact that you do not have overlapping polygons then you would be ok - Colin's recommendation in that scenario could then be sound. However, with polygons all over the place you should check on Area aswell as centroid to give improved reliability. An SQL Group By clause with Area(), Centroidx(obj) and Centroidy(obj) could do the trick. Still doesnt completely sort it though. At the end of the day a duplicate polygon has the exact same nodes. This means that all nodes in Polygon A have to be compared against all nodes in Polygon B. At least by finding the polygons with the same area and/or centroid you could start there - greatly minimizing processing time. Although node comparison isnt too difficult to do I would be interested to hear if any has worked on real-geo-de-duping(!) - perhaps there are other ways that the more mathematically minded amongst us can divulge?! Regards Doug www.gis-solved.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Colin Henderson Sent: 12 March 2002 10:12 To: paradigm Cc: [EMAIL PROTECTED] Subject: RE: MI-L Eliminating duplicate Polygons You could do a loop through the layer and get each object, query the object to find out its centroid co-ordinates and then query to see if any others have the same. Then you can just delete the identical polygons. The mapbasic user's guide or help files are as good a place as any to start learning mapbasic. ------------------------------- Kind Regards, Colin Henderson GI Developer Ordnance Survey Tel: +44 (0)2380 79 2327 mailto:[EMAIL PROTECTED] ------------------------------- -----Original Message----- From: paradigm [mailto:[EMAIL PROTECTED]] Sent: 11 March 2002 08:10 To: [EMAIL PROTECTED] Subject: MI-L Eliminating duplicate Polygons Hello, Iam new to mapbasic programming. I have hands-on experience on visual basic and SQL. Can anyone suggest me books to start with. First task given to me is to write a program to eliminate duplicate polygons in the same layer. I tried with correlated subquery in the mapbasic window. Unfortunately correlated subqueries are not supported by mapbasic. Please let me know if anyone has source code or knows method to eliminate duplicate polygons in the same layer. Anand. _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body. ******************************************************************** This Email and any attachments has been virus checked upon receipt at the OS and is free of all known viruses. ******************************************************************** *************************************************************** For more information on Ordnance Survey products and services, visit our web site at http://www.ordnancesurvey.co.uk *************************************************************** _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body. _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body.
