# Simplifying Lines and Polygons

7 replies to this topic

### #1 Keith Posted 12 March 2009 - 09:27 AM

Keith

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I am working on a series of maps at a continent level and am simplifying some of the base map layers. I have been using trial and error to try and get the level of simplification that looks good to my eye. My question is if there is a more scientific or best practice that could help speed up this process? I was thinking that there might be some rules that correlate the map scale with the simplification.

Any ideas?

### #2 Charles Syrett Posted 12 March 2009 - 10:57 AM

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If you want a level of simplification that looks right to the eye, why not just draw? You know.....trace the data? It takes a lot less time, and is a lot more enjoyable, than most people would suspect. And it's guaranteed to give you the result you want, especially since computer technology has obviated the need for drawing skills (e.g., pen and ink).

Or....if that's just not practical, try this (most excellent) tool: http://www.mapshaper.org/

Charles Syrett
Map Graphics
http://www.mapgraphics.com

I am working on a series of maps at a continent level and am simplifying some of the base map layers. I have been using trial and error to try and get the level of simplification that looks good to my eye. My question is if there is a more scientific or best practice that could help speed up this process? I was thinking that there might be some rules that correlate the map scale with the simplification.

Any ideas?

### #3 Keith Posted 12 March 2009 - 11:21 AM

Keith

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If you want a level of simplification that looks right to the eye, why not just draw? You know.....trace the data? It takes a lot less time, and is a lot more enjoyable, than most people would suspect. And it's guaranteed to give you the result you want, especially since computer technology has obviated the need for drawing skills (e.g., pen and ink).

Charles Syrett
Map Graphics
http://www.mapgraphics.com

I am working on a series of maps at a continent level and am simplifying some of the base map layers. I have been using trial and error to try and get the level of simplification that looks good to my eye. My question is if there is a more scientific or best practice that could help speed up this process? I was thinking that there might be some rules that correlate the map scale with the simplification.

Any ideas?

I usually do redraw with lines (Highways or rivers) but have not had success with political boundaries. The level of accuracy I achieve and the time I put in usually make running a simplification more accurate and a lot less time consuming in order to have decent topology. The results look good as well. I am always a little concerned with amount of simplification and always so a quick comparison to the original file .

Is there a better way to draw these complex political boundaries that keeps the topology in tact?

### #4 Michael Schmeling Posted 12 March 2009 - 11:25 AM

Michael Schmeling

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I have good success with drawing the state area in black/white to a high resolution .png file and then autotracing the .png file with Illy. You can adjust the resolution by choosing the png file resolution and by playing with the autotrace options in Illy. You can even automate the process with a script.

### #5 Charles Syrett Posted 12 March 2009 - 11:27 AM

Charles Syrett

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Looks like you quoted my reply before I edited it. here's what I added:
Or....if that's just not practical, try this (most excellent) tool: http://www.mapshaper.org/

That being said, I would still prefer to draw. Maybe it's just my obsession with having complete control over the process.

Charles Syrett
Map Graphics
http://www.mapgraphics.com

I usually do redraw with lines (Highways or rivers) but have not had success with political boundaries. The level of accuracy I achieve and the time I put in usually make running a simplification more accurate and a lot less time consuming in order to have decent topology. The results look good as well. I am always a little concerned with amount of simplification and always so a quick comparison to the original file .

Is there a better way to draw these complex political boundaries that keeps the topology in tact?

### #6 MapMedia Posted 12 March 2009 - 09:46 PM

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If you really want to keep topology tight and a consistent simplification, I would use ArcMap's generalize polygon tool or MapShaper.

### #7 frax Posted 13 March 2009 - 02:29 AM

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to redraw polygons with decent topology - try live paint in illy, it helps a lot!
Hugo Ahlenius
Nordpil - custom maps and GIS
http://nordpil.com/

### #8 eli Posted 23 March 2009 - 01:32 PM

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