Expanding a polygon

Blammo bob.basques at CI.STPAUL.MN.US
Tue Feb 28 09:04:36 EST 2006


Chip,

Hmmm, I wonder if MapServer could do it with a projection setting.  I 
have no idea what the projection would be, but the hard part would be 
picking a base point automatically for each center of every polygon, 
possibly a Centroid.  Don't know if this is possible.

Just a thought.   If you were trying to build a popout button for each 
state for example, you could use a sherical projection and make every 
state look like it's popping out from the center of the screen.  Hmmm, 
I'll have to look at that sometime.

I do know that I could write something in AutoCAD Map to do this.  You 
would end up with either a lot of overlapping Polygons in a single SHP 
file, or a seperate SHP file for each State with the new Polygon in it.

bobb


Marc Jacquin wrote:

>Chip,
>
>An easy way for doing this is to store your polygons in PostGis - use
>shp2psql - (now packaged with PostGreSQL), and use the buffer function =
>in
>PostGis. You may then use PostGis instead of shapefiles or export it =
>into
>shapefile again with pgsql2shp.
>
>Another one is to use the various version of Java Topolgy Suite, GEOS in
>C++, NetTopologySuite in C#.
>
>Marc=20
>
>-----Message d'origine-----
>De=A0: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] =
>De la
>part de Chip Taylor
>Envoy=E9=A0: mardi 28 f=E9vrier 2006 14:35
>=C0=A0: MAPSERVER-USERS at LISTS.UMN.EDU
>Objet=A0: [UMN_MAPSERVER-USERS] Expanding a polygon
>
>I need a tool that can take a shape file with a polygon, such as a state
>boundary, and expand it x amount in all directions.  For example, take a
>shapefile of the boundary of the State of Tennessee and expand the =
>polygon
>.5 degrees in all directions.  Anyone know of such a tool?
>
>Chip Taylor
>
>
>  
>



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