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Maintain edge alignments while smoothing in MAPub and Illustrator?

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#1
David Medeiros

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I'm working with a set of polygons (park areas) where many of the areas share edges. The data is originally from a.shp file so the curves are all made of ugly straight line segments. My usual procedure to tackle this problem is use the simplify tool in MAPublisher which maintains the topology while reducing the number of points in each line or polygon but keep straight lines. I then use a 99% simplify function in Illustrator which smooths the lines and adds bezier curves but slightly changes the topology between adjacent polygons. 99% usually keeps the edges close enough to not mater if they are not exactly matched. My problem is that for this map I need the edges to continue to be perfectly aligned to each other because they will be offset inwards and set to be partially transparent, meaning any overlap or gap will be immediately obvious on the map.

Is there a way to get smoothed lines with out loosing my edge alignment?

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#2
razornole

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I haven't found an easy/quick way to do it. I'll follow this thread in case someone out there wants to enlighten us.

The method that I use requires a lot of copy and pasting forward, and then cutting and joining segments. This of course is after I smooth the lines. I made a large base map of the US this way, I had to copy, paste, cut, and join every shared border (made me love the ocean that much more). It took a lot of time, but was well worth it to get the GIS out of my map.

If there are not many anchor points you can always use the indirect selection tool to deselect the anchor points before you smooth.

kru
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#3
Hans van der Maarel

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Are the edges aligned properly in your source data? How important are your MAPublisher attributes to you? If your answers are "yes" and "not" you can try this:
  • Use the pathfinder tools to turn the areas into single lines
  • Smooth them as per the process you described above
  • Use the pathfinder tools again to turn them back to areas

Of course this will destroy your attributes, so it's probably a good idea to try this out on a copy of your layer first.
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#4
jrat

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if you have Arcmap 10 you could put your .shp into a geodatabase. Using the map topology tools remove all verticies but the end points then right click and change from a straight segment to a curved or bezier segments. If you do this while using the topology edit tool your coincidence will be maintained.

#5
cartdeco

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Hi David,

Use MAPublisher's Simplify Line tool to achieve this. Note that lines between nodes will still be straight lines, though you should be able to reduce the number of points by a significant margin by using this method. As Hans alluded to, using Illustrator's Simplify Path tool will smooth the lines with bezier curves, but all attribute data will be lost. You may wish to duplicate your polygon layer before attempting the smooth.

The best approach would be to use a combination of the MP Simplify Line tool to remove as many points as is practical, then run the Illustrator simplify line tool to get you beziers.

I don't think you'll get a perfect result, but you may want to disguise the small gap by putting a stroke over the top for the boundary of the polygon.

Another useful workflow to avoid gaps is use Illustrator's Live Paint tool. Have a look at Nathaniel Kelso's blog for the procedure.

http://kelsocartogra...om/blog/?p=2798

Regards,

Craig
Craig Molyneux
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craig.molyneux@spatialvision.com.au

#6
Jacques Gélinas

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If you have CS5 you might also look into the new shape builder tool. I really like that new feature in CS5.

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Jacques Gélinas
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#7
David Medeiros

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Are the edges aligned properly in your source data? How important are your MAPublisher attributes to you? If your answers are "yes" and "not" you can try this:

  • Use the pathfinder tools to turn the areas into single lines
  • Smooth them as per the process you described above
  • Use the pathfinder tools again to turn them back to areas

Of course this will destroy your attributes, so it's probably a good idea to try this out on a copy of your layer first.


Thanks, Hans,

Edges are perfectly aligned in source data. I don't need the attributes in the final map but do need them to classify areas by type, but that can be handled a number of ways.

I tried the various tools in pathfinder and figured out that outline will give me single lines, broken at every area intersection, which I can then smooth in Illustrator. But none of the tools I tried will put them back together as whole, correct, polygons. What specific function in pathfinder should i be using for this?

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www.mapbliss.com

 


#8
Hans van der Maarel

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I tried the various tools in pathfinder and figured out that outline will give me single lines, broken at every area intersection, which I can then smooth in Illustrator. But none of the tools I tried will put them back together as whole, correct, polygons. What specific function in pathfinder should i be using for this?


Divide (bottom row, leftmost button) does the trick. But it may just give up if you have a lot of complex lines. It's far from a perfect solution, I'll readily admit that.
Hans van der Maarel - Cartotalk Editor
Red Geographics
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#9
David Medeiros

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I tried the various tools in pathfinder and figured out that outline will give me single lines, broken at every area intersection, which I can then smooth in Illustrator. But none of the tools I tried will put them back together as whole, correct, polygons. What specific function in pathfinder should i be using for this?


Divide (bottom row, leftmost button) does the trick. But it may just give up if you have a lot of complex lines. It's far from a perfect solution, I'll readily admit that.


I'll try again later today, but I wasn't getting any results with the Divide function. I may also try jrats option since i have Arc10 at work.

Thanks all.

Edited to add: correction, I just tried it again and this time it worked perfectly, thanks Hans!

GIS Reference and Instruction Specialist, Stanford Geospatial Center.

 

www.mapbliss.com

 





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