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#1
burwelbo

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Does anyone know how to make proper Cul-De-Sacs for subdivisions using ArcGIS 9.0? I have road centerlines but I want to add the cul-de-sacs. One method I thought of was to extract the end vertices and make a seperate point file, then symbolize that to look like the cul-de-sac. Are there any other methods?

Thanks
Bruce

#2
Hans van der Maarel

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Just thinking out loud, I don't use ArcGIS, so I'm not sure whether this is actually possible...

I assume you want to show the cul-de-sac as a little circle at the end of the street line. Would it be possible to set up a directional line style in ArcGIS? I.e. use a style that has a standard style but with a different "end" (but not start!). Then change the order of the vertices so the end of the line is always at the cul-de-sac (I think I could pull that one off with FME).

Alternatively, the point method will work too, but then you'll be stuck with a lot of extra, unnecessary, points.
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#3
burwelbo

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I tried that but here were a few problems.

1. The end nodes were not always at the end where the cul-de-sac was (wrong direction).
2. It didn't produce the road casing effect I wanted. It just produced a circle on top. With the point idea at the end at least I can put the point underneath the road.

What do other people do? Just produce polygons. That doesn't seem very efficient. What can you do in Illustrator?

#4
CHART

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Maybe using a round cap at the end of the line in Illustrator would do the trick depending on the cul de sac effect your are looking for.
Chart

#5
Charlie Frye

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There's nothing that's going to make a really nice cul-de-sac based on centerlines and points. The best you can do there is to have a point layer where you've snapped point features to the endpoints of road lines with cul-de-sacs. You can symbolize the lines with a cased line and the points with a multi-layer marker that emulates the line cases. Then, the trick is to put both layers into a group layer and use the symbol level drawing feature at the group layer level to integrate the drawing of the layered symbols.

The reason you'll need to use the point layer is because not all roads spurs are cul-de-sacs, and if you want to get fancy, some are not centered at the end of the road. That means the editing is manual and you'll need the imagery to know whether a cul-de-sac actually exists. It's a shame as most road line data doesn't have an attributed specifying the line as ending in a cul-de-sac. I say that because at 9.2 we added, via the representations symbology a way to automatically find cul-de-sacs; but it doesn't know how to tell whether a street line is a cul-de-sac or not without an attribute; thus, once you have 9.2, use that tool and then just manually turn off the non-cul-de-sacs, as that will likely be less editing. As a benchmark, it took me about 2 hours to do this for a 1:24,000 quad sheet (Austin East) in Austin, TX.

You can get even fancier by creating a nicer looking cul-de-sac symbol (I've never gotten around to it) as an .emf file that you can import as a picture marker symbol. However, then you'll need to add a rotation angle attribute to the cul-de-sac point features and use the rotation option (Advanced button on symbology tab for point layers). That will require a good bit more time to edit; though in 9.2 with the representation symbology , you will be able to interactively rotate the marker, so not nearly as bad.

Have fun,

Charlie
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#6
burwelbo

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Thanks Charlie

So in 9.2 we should be able to assign an attribute specifying whether a road is a cul-de-sac or not. What about creating buffers around a point and line feature as a group layer and then dissolving them together? If the point wasin the middle of the cul-de-sac should it not work? I guess what you need is a method of specifying a radius for the vertex at the end of each line.

#7
Charlie Frye

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The buffer/merge method is fine too--it will give you effectively the same result, though and I think any resulting graphics files will be rather large. I would also warn that merging may produce some very large polygons (vertex-rich with many interior parts) that may choke or slow down ArcMap and other graphics software packages.

It's not just the radius for the vertex, it's also an elongation and second inflection point (on each side) connecting the sac to the road (the shape should look a bit more like a standard light bulb, not an oven light bulb).

Charlie
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