topic Re: create point shapefile of street intersections from polyline - ArcEditor in Data Management Questions

create point shapefile of street intersections from polyline - ArcEditor

MichaelCatsos — Wed, 09 Feb 2011 22:22:15 GMT

I'm trying to create a point shapefile of street intersections in downtown Phoenix, somehow deriving the points from a lone street centerline layer. I have tried extracting polyline nodes to points, but nodes do not exist at all of the necessary intersections. Intersect-related solutions don't seem to be any help since I am only working with one layer.

I'm not experienced enough to understand most scripting. Is there any procedure to split polyline features into segments between each intersection? After that I could extract the nodes, then turn them into points.

Another option I have explored is creating a small buffer around the polyline features. Theoretically, the points where the buffers around each segment overlap represent the intersections. This method is more inclusive, including all the potential intersections, but I can not figure out how to "overlay" the buffer with itself. Is there some way to use overlay to extract the small polygons where the individual buffered segments overlap, even though they are all in the same layer?

Re: create point shapefile of street intersections from polyline - ArcEditor

JohnSobetzer — Thu, 10 Feb 2011 12:37:40 GMT

I've used Hawth's Analysis Tools (free) to produce points at line intersections in the same layer, but I think it creates duplicates at each location which I removed by running a clean. That was many years ago. ETGeowizards has a Renode Wizard that from the help says it would analyze a line layer and it could create points representing the regular nodes where two lines intersect but it isn't one of the free tools.

Re: create point shapefile of street intersections from polyline - ArcEditor

AlexeyTereshenkov — Sat, 19 Feb 2011 17:09:14 GMT

Hi,

Could creating a geometric network solve the problem? (ArcCatalog > Geodatabase > Feature dataset > Geometric network). Junctions will be created automatically at the intersections of the streets.

Re: create point shapefile of street intersections from polyline - ArcEditor

BRaffel — Tue, 22 Feb 2011 18:14:07 GMT

You could use the Planarize tool - this will break all of the lines where they intersect.

Re: create point shapefile of street intersections from polyline - ArcEditor

JoshuaDamron — Wed, 09 Mar 2011 18:09:03 GMT

Alexey,
Thank you for your post!

Great idea, I just created a geometric network to place points at all of our street intersections. Quick and easy, had to do a little cleanup work as it placed points in all the cul-de-sac's as well. Now to complete my count on how many STOP signs we have...

I like it when I can place a thousand points in a few seconds 🙂

-Joshua

Re: create point shapefile of street intersections from polyline - ArcEditor

AlexeyTereshenkov — Wed, 09 Mar 2011 19:37:41 GMT

Hi Joshua,

Glad it worked out well for you. Geometric networks are indeed very good! But if you work with street data extensively, I encourage you to take a look at the Network Analyst geoprocessing tools - we have got quite a few new useful ones (ArcGIS 10). What's more, you can define your connectivity rules for your streets (end vertex or any vertex) and obtain system junctions that will get created upon the build of the network.

Consider using Topology toolbar as BRaffel mentioned as well! 🙂

Re: create point shapefile of street intersections from polyline - ArcEditor

RickEhlin__Jr — Fri, 06 May 2011 14:16:20 GMT

Is there someway to transfer the centerline names to a intersection_name field in the point file?

Re: create point shapefile of street intersections from polyline - ArcEditor

DarrenWiens2 — Fri, 06 May 2011 21:17:20 GMT

I just wanted to point out that you absolutely can run the intersect tool with only one input, select point as output type, and get the intersections.

Re: create point shapefile of street intersections from polyline - ArcEditor

AlexeyTereshenkov — Mon, 09 May 2011 06:02:32 GMT

Thank you very much for pointing this out, I have totally missed this!

However, I believe that creating a geometric network in the case of having billions of links is still more efficient time-wise. After editing the underlying data, to get the new points of intersection is a matter of rebuilding network, but when running the Intersection tool one is supposed to run the whole streets layer as the input.

Re: create point shapefile of street intersections from polyline - ArcEditor

RickEhlin__Jr — Mon, 09 May 2011 11:50:12 GMT

It looks like we've established how to get the point file (intersections) created, but that file has no usable data in it. How would you go about getting the street names that intersect into the intersection file? I can't find an automated solution to this...???

Re: create point shapefile of street intersections from polyline - ArcEditor

AlexeyTereshenkov — Mon, 09 May 2011 12:32:55 GMT

Rick, the attributes of the road segments will be transferred to the point features appropriately. Try to run the Intersect tool and check the attribute table of the output point layer.

Re: create point shapefile of street intersections from polyline - ArcEditor

RickEhlin__Jr — Mon, 09 May 2011 13:18:01 GMT

Rick, the attributes of the road segments will be transferred to the point features appropriately. Try to run the Intersect tool and check the attribute table of the output point layer.

I ran the intersect tool from toolbox and it worked.....BUT there are now points for every line that meets up there....time to figure out how to unite all data into one point.

Re: create point shapefile of street intersections from polyline - ArcEditor

JimW1 — Tue, 10 May 2011 19:45:02 GMT

I ran the intersect tool from toolbox and it worked.....BUT there are now points for every line that meets up there....time to figure out how to unite all data into one point.

Make a dissolve field that is a concatenation of the LAT/LON or X/Y.
So for example:
DISSOLVEID = �??-75.123456_45.123456�?�
Each point at this location should have the same string. You can then dissolve by the DISSOLVEID string.
Otherwise there is always topological buffers in VBA/Python.

Re: create point shapefile of street intersections from polyline - ArcEditor

MikeHargreaves — Wed, 11 May 2011 18:57:00 GMT

Okay, I'm confused. I did the Intersect on my centerline, setting the output to point. It created a multipoint feature, so I ran the multipoint to singlepoint. Then I added the DissolveID field, and did the dissolve, setting the street name first and last as the statistics fields. The problem I'm getting, is that at a T-junction, I have three points, with two having the same name, and sometimes the First and Last select those two and not the one with the different name. What happens when I have more than two streets coming together at an intersection?

Re: create point shapefile of street intersections from polyline - ArcEditor

MikeHargreaves — Wed, 11 May 2011 22:38:56 GMT

Okay, I've managed to get something, though it is not pretty. Here are my steps:
1) Create Version of centerline that only has named streets
2) Dissolve on full street name (e.g. MAIN ST - this will remove duplicates later)
3) Use Intersect on this layer with output type = point
4) Add XY coordinates to new point layer and create DissolveID field and set to X_Y as mentioned above
5) Dissolve on DissolveID field to end up with only one point per intersection
6) Add new field to your Dissolved Named Streets layer - make 150-200 characters to hold 4-5 street names, then use Field Calculator to fill it with street name and add an underscore "_" at the end (e.g. MAIN ST_)
7) Do a Spatial Join with your target being the intersection points, and the Join Features being the dissolved named streets layer. Right click on your new field in the Field Map of Join Features, and under Merge Rule choose Join. After running, your end result should look something like A ST_1ST ST_ All streets at the intersection will be included (I got up to 4), and only once each if you did the original dissolve.
😎 Use Field calculator to strip the last "_" and then replace the rest with " & " - set the Parser to Python, then use the following: !YourFieldName!.rstrip('_') and then !YourFieldName!.replace('_',' & ') Your final will look like A ST & 1ST ST

Now, all I have to do is create a model, so I'll remember how to do it the next time...!

Re: create point shapefile of street intersections from polyline - ArcEditor

JimW1 — Fri, 13 May 2011 13:33:12 GMT

Sorry for the delay. Your methodology is good.

From my experience look out for T-Intersections, places where road names change, highway interchanges, and crazy intersections (5+) as the spatial join and attribute carry can be weak.

I went through this about a month ago for a Canada-wide road network and broke down and used the topological buffer tool in VBA to get really clean intersection attributes.

Re: create point shapefile of street intersections from polyline - ArcEditor

MikeHargreaves — Fri, 13 May 2011 14:52:06 GMT

Thanks Jim,

As far as I can tell, road name changes and T-intersections all look fine. I debated whether to remove my freeways and such with overpasses from the original layer, but decided to leave them in, even if they are not really intersections, since folks still like to reference those locations. As far as I can tell, we don't have any intersections in the County with more than 4 streets. The last time I made intersections a couple of years ago, I did use some code that I found that used the buffer, but it was very slow, and I think my product this time was actually cleaner. Maybe it is not the same buffer - the one I used did not put all the street names into one field, but instead put them into separate fields, and then I had to run a model to compare each field to the others to make sure it was not a duplicate before adding it to the final intersection label field. After creating the new intersections this time, however, I found that someone was using those individual street name fields... So, does anyone have a suggestion on how I can strip individual streets from a field containing something like MAIN ST & 1ST ST & B ST ? I could load it onto the mainframe and use a programming language that I know, but I'm sure there should be a way to do it in Python - I just don't really know it at all. Seems like I should be able to search for the & and get its location, and then use that do a strip or something...

Re: create point shapefile of street intersections from polyline - ArcEditor

DarrenWiens2 — Sun, 12 Dec 2021 07:56:19 GMT

So, does anyone have a suggestion on how I can strip individual streets from a field containing something like MAIN ST & 1ST ST & B ST ?

In Python, you'd read the field values, using a SearchCursor, into a string variable. Then, use the Python .split method. For example:

array = yourstring.split("&")
firststreetname = array[0]
secondstreetname = array[1]
thirdstreetname = array[2]

Re: create point shapefile of street intersections from polyline - ArcEditor

MikeHargreaves — Fri, 13 May 2011 16:32:46 GMT

Thanks - that looks like just what I need. Will there be any problems when I try thirdstreetname = array[2] if there is not a third street?

Re: create point shapefile of street intersections from polyline - ArcEditor

DarrenWiens2 — Sun, 12 Dec 2021 07:56:22 GMT

Yes, there will be problems. I think you can tackle this with:

for i in range(0,len(array))
    streetname = array

...it may be len(array)-1