Nathan, I think you should go in a different direction. Way not combining all the records in your tables into one table. Then you can select all records and combine them into one single object (Unless the number of nodes gets to big ...)
And finally you can do an areacalculation of this single object. You could also insert one layer at a time into the new table and for each new layer you want to insert, you first select everything from the new table, set this as target, then you select everything from the layer to insert and do an erase. Now every part of the objects in the new layer tha overlap any part of the objects in the layer to insert will be deleted. Finally you insert the records from the layer into the new layer. Again you finish by doing an area calcualtion, this time by Selecting "Sum(CartesianArea(OBJ, "sq m")" or Sum(Area(OBJ, "sq m"), depending on your coordsys HTH, Peter Horsbøll Møller GIS Developer, MTM Geographical Information & IT COWI A/S Odensevej 95 DK-5260 Odense S. Denmark Tel +45 6311 4900 Direct +45 6311 4908 Mob +45 5156 1045 Fax +45 6311 4949 E-mail [EMAIL PROTECTED] http://www.cowi.dk/gis -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Nathan Carr Sent: Wednesday, May 03, 2006 12:51 PM To: mapinfo-l@lists.directionsmag.com Subject: [MI-L] Summing up areas of several layers, exclusive of overlap Hiya, I've got a nice task of adding up the areas of several layers excluding multiple counts of those polygons that overlap. In other words... I need to get the cumulative sum of all the areas of features in several layers, but not counting twice those layers that overlap. I imagine that I can do it with a combination of the SQL functions of CASE and SUM and AREA and the MapInfo/Spatialware commands of INTERSECTS and ENTIRELY WITHIN... But, I thought I'd see if anyone has any other ideas or anything I can base things on. One problem I can initially see is that how do you seperate into two areas the two parts of a polygon that lie inside and outside of another. And the CASE conditional must be repeated in a quite a complex way when dealing with about six layers. Thanks for any pointers, Nathan ---------------(\./)--------------- Nathan Carr GIS Developer LLPG/LSG Custodian & ALO Swale Borough Council Email : [EMAIL PROTECTED] Phone : 01795 417 337 Mobile : 07957 461 685 This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager at [EMAIL PROTECTED] This message has been scanned for viruses by BlackSpider MailControl - www.blackspider.com I.T. Services Swale Borough Council Visit http://www.swale.gov.uk _______________________________________________ MapInfo-L mailing list MapInfo-L@lists.directionsmag.com http://www.directionsmag.com/mailman/listinfo/mapinfo-l _______________________________________________ MapInfo-L mailing list MapInfo-L@lists.directionsmag.com http://www.directionsmag.com/mailman/listinfo/mapinfo-l
