Make overlaped lines thicker

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05-24-2011 06:01 AM
JoeFred
New Contributor
Hey everyone!

Would be very nice if someone could help me!

I have many Polylines which are representing routes. They are in one shapefile and some of them are overlapping each other. I want to make a kind of a traffic stream map where the frequented streets are thicker than others.

Somethink like that http://www.region-frankfurt.de/media/custom/1169_207_1_m.JPG?1142392280

Which is the most simple solution for that?

Thanks for helping me!
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JimW1
by
Occasional Contributor II
On one 'Bored Friday', I once did something similar:

I took my transit network and selected my base street layer by the transit routes. I then took the subset of the streets layer and ran the 'Feature to Point' (ArcInfo) tool on it to give me center points of those street polylines. I then buffered those points by 1m and ran a 'Spatial Join' on the buffers against the original transit routes. This gave me a count per street of the transit routes.

I joined the counts back to the streets layer subset and then set my line widths to reflect the join counts.

I've skipped a few steps and my data was all derived from the same base streets layer but after a few hours of playing with it I got a pretty decent-looking transit flow maps.

Unfortunately not as nice looking as your example but once the graphic designers got the PDF they made it better looking. I'm not at the same firm now otherwise I'd attach a sample.
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JoeFred
New Contributor
Thanks very much!!! Thats interesting!

But than the whole route will be thicker and not only this parts where the routes are overlapping right?
Or i split them before ?!

I hoped there is a much more easier solution. Like i have to add only a offset to the lines when they are overlapping or something like that. Or is that also a way?
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JimW1
by
Occasional Contributor II
Thanks very much!!! Thats interesting!

But than the whole route will be thicker and not only this parts where the routes are overlapping right?
Or i split them before ?!

I hoped there is a much more easier solution. Like i have to add only a offset to the lines when they are overlapping or something like that. Or is that also a way?


Yes the routes need to be split into equal parts for the counts to work. So the arc for each route running down say Main Street must be the exact same geometry. If your data isn't already like that then ignore my methodology.

My apologies too as I thought you'd already tried offsets.

I found offsetting to be inconsistent -mainly due to the direction of the underlying arcs. For offsets to work well each routing polyline needs to be drawn in the same direction.

I also played with cartographic representations on some eco-corridors and had some success but that was mostly a manual exercise and far too time consuming.

Sorry... I don't have an easy method for you. I'd be interested in if anyone has found one but I find this forum is a little light on pure cartography discussions with ArcMap. In my experience, few GISers spend much time on cartography unless that is a mandate of their position. I just got sick of graphic designers making horribly inaccurate maps and have tried to leverage some advanced graphics out of ArcMap to compete (sorry ranting).
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