RE: MI-L Combining Similar Polygons selectively.

[Robert Crossley]

Title: Combining Similar Polygons selectively.

If the length of the 10 fields is less than 254 characters in total, You could make a key field that could take all the data from the 10 fields, then combine using this field. Viz.

Add a field to your table,

Use Table > Update Column to Update this field with the expression field1+"-"+field2 etc.

Run Combine Objects Using Column using this field

 

-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Macdougall, Evan 1065
Sent: Saturday, January 06, 2001 3:17 AM
To: [EMAIL PROTECTED]
Subject: MI-L Combining Similar Polygons selectively.

Hello again, all....

        My problem has yet to be solved, to I will present it to you again with some of the background replies.  Let me update my previous stats.  I have 23 different fields in my table.  The map is broken down to reflect at least 10 of these fields.  I would like to be able to combine all polygons that have all 10 of those fields in common.  However, if only 9 are matching, but 1 is different, I don't want those polygons combined.  The problem with using the "Combine Objects Using Column" command is that it only looks at one field and ignores the other 9 and in the process I lose the rest of my map.  Is there a program/process by which I could combine all the polygons where all 10 of those fields (or any number of my choosing) match, but not combine the polygons where at least 1 of those fields do not match?  Thank you all for your help.

-Evan ([EMAIL PROTECTED])

<begin quote 'reply string'>

Ok,
        That works if the only thing I have as part of each county are the flood zones and maps.  Unfortunately, the counties also have the cities boundaries showing as well.  How can can get rid of the old map lines, while keeping the new maps lines AND the city boundaries?  It is not easy to re-create the city boundaries because many of them are extremely complex.  My table has 23 different fields in it.  21 of them have set values that are different from polygon to polygon.  Is there a way I can combine only the polygons that have all 21 of those neccessary fields matching?  Not just combining using 1 field, but all of them at the same time?  I don't want to combine different cities into one, i want them to stay separate.  Any process/program for doing that?

-Evan ([EMAIL PROTECTED])

        -----Original Message-----
From:   Will Mitchell [SMTP:[EMAIL PROTECTED]]
Sent:   Wednesday, January 03, 2001 12:23 PM
To:     Macdougall, Evan     1065; [EMAIL PROTECTED]
Subject:        RE: MI-L Combining matching polygons

        Hi Evan,
 
From your description it sounds like you can use the TABLE Menu Command > "Combine Objects Using Column".
 
This will create the merged polygons that you need either as new objects in your same table or into a new table.  I find it easier to just let them be added to the existing table, then you can save them out as a new file and revert the base table...this way you don't have to set up a blank table with a matching field structure ahead of time to dump into.

         
Good luck.
Will Mitchell
Mitchell Geographics, Inc.
496 Congress Street
Portland, ME 04101
www.mitchellgeo.com
ph 207.879.7769
fx 207.253.5756

        -----Original Message-----
From: [EMAIL PROTECTED] [ <mailto:[EMAIL PROTECTED]>]On Behalf Of Macdougall, Evan 1065
Sent: Wednesday, January 03, 2001 2:55 PM
To: '[EMAIL PROTECTED]'
Subject: MI-L Combining matching polygons



        Hello all,
        I have a perplexing problem that maybe there is a solution to.  If you can help me, let me know.

        Here's my problem:  I am working with FEMA flood maps for various counties for the U.S.  Each county is broken down into a variable number of different maps, each showing 3, 4 or more different flood zones.  However, sometimes, the maps change shapes and sizes.  So, say a county that once was broken up into a 4x4 grid is revised by FEMA and is now broken up into a 7x7 grid.  I can use gridmaker to make grids to match the net map designs, that is not a problem.  However, the old map boundaries are still there and i now have side-by-side polygons with the same information sitting next to each other, all over the map.  Is there there a program/process that will compress the graphical data by combining adjacent polygons which have matching data?  So, is there a way that I can remove the old map boundaries after cutting in the new ones without having to go map-by-map, polygon-by-polygon to combine the ones with matching info myself?  Any help would be very much appreciated  (very very much).

        -Evan ([EMAIL PROTECTED])

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