RE: [MI-L] Determining how many polygons occupy the same area

[Llewellyn, David]

Alan,   I had a project to do something like this and wrote a MapBasic program to do it (description below). I would be happy to forward you the source and or exe if you are interested. Note that the program could take quite a long time to run depending on the complexity of the table of polygons being analysed.   'Description: This program is intended to operate on a MapInfo table which consists of region objects, 'some or all of which may overlap each other. The program takes each object from the input table and 'splits it into separate sections wherever it overlaps with any other region in the same table. 'The output table which results from this splitting operation is saved as a new table with the input 'table name and "_PCL" appended. The PCL table retains the attributes of the input table and an extra 'integer column is added which is populated with a number indicating the number of input regions overlapping 'in each parcelised region. 'A second output table is created with the name of the input table and "_Olap" appended. This table is the 'result of a 'combine using column' operation performed on the PCL table, using the integer column populated 'in the above process. The Olap table will therefore contain a number of multi-region objects, each of which 'contain an integer value attribute that indicates the number of overlapping regions at any point across the 'table.   Cheers David L   -----Original Message----- From: Alan Silvester [mailto:[EMAIL PROTECTED] Sent: Friday, 21 April 2006 10:10 PM To: mapinfo-l@lists.directionsmag.com Subject: [MI-L] Determining how many polygons occupy the same area   Dear List,   Does anybody know how I can work out how many polygons cover the same area? I have a layer of polygons that overlap one another in various places. I need to cookie cut them into one another so I am left with a layer of smaller polygons and determine how many of those occupy exactly the same area. The example diagram below shows the idea I have at the moment whereby 2 polygons overlap one another, and get split to produce 4 polygons, but I do not know quite how to go about it?     Incidentally if there is an easier way of doing this, all suggestions greatly received.   Regards   Alan       ***This Email, together with any attachments is intended for the addressee only. If you have received this Email in error please inform the sender immediately by return Email. Alternatively you can ring the National Native Title Tribunal on the toll free number 1800 640 501 and report the error. Please delete the Email and any copies from your computer and/or computer network. The Tribunal does not warrant that this email is virus free. The Tribunal has also implemented content filtering of Emails to restrict inappropriate and spam emails being received. Other emails which may contain viruses may also be blocked. In either case, and in any case the email may not reach its intended recipient. If the email is important you may wish to see confirmation of its receipt by placing that request in the text of the email. Please resend the email if you haven't received that confirmation as requested. ***

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